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Places to Intervene in a System
Donella H. Meadows
Vadim Petrakov / Shutterstock.com
Editors' note: This article, first published in Whole Earth in winter 1997, is from NPQ's summer 2015 edition, "Nimble Nonprofits: The Land of the Frugal Visionary." We thank the Donella Meadows Institute for their kind permission.
Folks who do systems analysis have a great belief in "leverage points." These are places within a complex system (a corporation, an economy, a living body, a city, an ecosystem) where a small shift in one thing can produce big changes in everything.
The systems community has a lot of lore about leverage points. Those of us who were trained by the great Jay Forrester at MIT have absorbed one of his favorite stories. "People know intuitively where leverage points are. Time after time I've done an analysis of a company, and I've figured out a leverage point. Then I've gone to the company and discovered that everyone is pushing it in the wrong direction!"
The classic example of that backward intuition was Forrester's first world model. Asked by the Club of Rome to show how major global problems—poverty and hunger, environmental destruction, resource depletion, urban deterioration, unemployment—are related and how they might be solved, Forrester came out with a clear leverage point: Growth. Both population and economic growth. Growth has costs—among which are poverty and hunger, environmental destruction—the whole list of problems we are trying to solve with growth!
The world's leaders are correctly fixated on economic growth as the answer to virtually all problems, but they're pushing with all their might in the wrong direction.
Counterintuitive. That's Forrester's word to describe complex systems. The systems analysts I know have come up with no quick or easy formulas for finding leverage points. Our counterintuitions aren't that well developed. Give us a few months or years and we'll model the system and figure it out. We know from bitter experience that when we do discover the system's leverage points, hardly anybody will believe us.
Very frustrating. So one day I was sitting in a meeting about the new global trade regime, NAFTA and GATT and the World Trade Organization. The more I listened, the more I began to simmer inside. "This is a HUGE NEW SYSTEM people are inventing!" I said to myself. "They haven't the slightest idea how it will behave," myself said back to me. "It's cranking the system in the wrong direction—growth, growth at any price!! And the control measures these nice folks are talking about—small parameter adjustments, weak negative feedback loops—are PUNY!"
Suddenly, without quite knowing what was happening, I got up, marched to the flip chart, tossed over a clean page, and wrote: "Places to Intervene in a System," followed by nine items:
9. Numbers (subsidies, taxes, standards).
8. Material stocks and flows.
7. Regulating negative feedback loops.
6. Driving positive feedback loops.
5. Information flows.
4. The rules of the system (incentives, punishments, constraints).
3. The power of self-organization.
2. The goals of the system.
1. The mindset or paradigm out of which the goals, rules, feedback structure arise.
Everyone in the meeting blinked in surprise, including me. "That's brilliant!" someone breathed. "Huh?" said someone else.
I realized that I had a lot of explaining to do.
In a minute I'll go through the list, translate the jargon, give examples and exceptions. First I want to place the list in a context of humility. What bubbled up in me that day was distilled from decades of rigorous analysis of many different kinds of systems done by many smart people. But complex systems are, well, complex. It's dangerous to generalize about them. What you are about to read is not a recipe for finding leverage points. Rather it's an invitation to think more broadly about system change.
That's why leverage points are not intuitive.
Numbers ("parameters" in systems jargon) determine how much of a discrepancy turns which faucet how fast. Maybe the faucet turns hard, so it takes a while to get the water flowing. Maybe the drain is blocked and can allow only a small flow, no matter how open it is. Maybe the faucet can deliver with the force of a fire hose. These considerations are a matter of numbers, some of which are physically locked in, but most of which are popular intervention points.
Consider the national debt. It's a negative bathtub, a money hole. The rate at which it sinks is the annual deficit. Tax income makes it rise, government expenditures make it fall. Congress and the president argue endlessly about the many parameters that open and close tax faucets and spending drains. Since those faucets and drains are connected to the voters, these are politically charged parameters. But, despite all the fireworks, and no matter which party is in charge, the money hole goes on sinking, just at different rates.
The amount of land we set aside for conservation. The minimum wage. How much we spend on AIDS research or Stealth bombers. The service charge the bank extracts from your account. All these are numbers, adjustments to faucets. So, by the way, is firing people and getting new ones. Putting different hands on the faucets may change the rate at which they turn, but if they're the same old faucets, plumbed into the same system, turned according to the same information and rules and goals, the system isn't going to change much. Bill Clinton is different from George Bush, but not all that different.
Numbers are last on my list of leverage points. Diddling with details, arranging the deck chairs on the Titanic. Probably ninety-five percent of our attention goes to numbers, but there's not a lot of power in them.
Not that parameters aren't important—they can be, especially in the short term and to the individual who's standing directly in the flow. But they RARELY CHANGE BEHAVIOR. If the system is chronically stagnant, parameter changes rarely kick-start it. If it's wildly variable, they don't usually stabilize it. If it's growing out of control, they don't brake it.
Whatever cap we put on campaign contributions, it doesn't clean up politics. The Feds fiddling with the interest rate haven't made business cycles go away. (We always forget that during upturns, and are shocked, shocked by the downturns.) Spending more on police doesn't make crime go away.
However, there are critical exceptions. Numbers become leverage points when they go into ranges that kick off one of the items higher on this list. Interest rates or birth rates control the gains around positive feedback loops. System goals are parameters that can make big differences. Sometimes a system gets onto a chaotic edge, where the tiniest change in a number can drive it from order to what appears to be wild disorder.
Probably the most common kind of critical number is the length of delay in a feedback loop. Remember that bathtub on the fourth floor I mentioned, with the water heater in the basement? I actually experienced one of those once, in an old hotel in London. It wasn't even a bathtub with buffering capacity; it was a shower. The water temperature took at least a minute to respond to my faucet twists. Guess what my shower was like. Right, oscillations from hot to cold and back to hot, punctuated with expletives. Delays in negative feedback loops cause oscillations. If you're trying to adjust a system state to your goal, but you only receive delayed information about what the system state is, you will overshoot and undershoot.
Same if your information is timely, but your response isn't. For example, it takes several years to build an electric power plant, and then that plant lasts, say, thirty years. Those delays make it impossible to build exactly the right number of plants to supply a rapidly changing demand. Even with immense effort at forecasting, almost every electricity industry in the world experiences long oscillations between overcapacity and undercapacity. A system just can't respond to short-term changes when it has long-term delays. That's why a massive central-planning system, such as the Soviet Union or General Motors, necessarily functions poorly.
A delay in a feedback process is critical RELATIVE TO RATES OF CHANGE (growth, fluctuation, decay) IN THE SYSTEM STATE THAT THE FEEDBACK LOOP IS TRYING TO CONTROL. Delays that are too short cause overreaction, oscillations amplified by the jumpiness of the response. Delays that are too long cause dampened, sustained, or exploding oscillations, depending on how much too long. At the extreme they cause chaos. Delays in a system with a threshold, a danger point, a range past which irreversible damage can occur, cause overshoot and collapse.
Delay length would be a high leverage point, except for the fact that delays are not often easily changeable. Things take as long as they take. You can't do a lot about the construction time of a major piece of capital, or the maturation time of a child, or the growth rate of a forest. It's usually easier to slow down the change rate (positive feedback loops, higher on this list), so feedback delays won't cause so much trouble. Critical numbers are not nearly as common as people seem to think they are. Most systems have evolved or are designed to stay out of sensitive parameter ranges. Mostly, the numbers are not worth the sweat put into them.
The plumbing structure, the stocks and flows and their physical arrangement, can have an enormous effect on how a system operates.
When the Hungarian road system was laid out so all traffic from one side of the nation to the other had to pass through central Budapest, that determined a lot about air pollution and commuting delays that are not easily fixed by pollution control devices, traffic lights, or speed limits. The only way to fix a system that is laid out wrong is to rebuild it, if you can.
Often you can't, because physical building is a slow and expensive kind of change. Some stock-and-flow structures are just plain unchangeable.
The baby-boom swell in the U.S. population first caused pressure on the elementary school system, then high schools and colleges, then jobs and housing, and now we're looking forward to supporting its retirement. Not much to do about it, because five-year-olds become six-year-olds, and sixty-four-year-olds become sixty-five-year-olds predictably and unstoppably. The same can be said for the lifetime of destructive CFC molecules in the ozone layer, for the rate at which contaminants get washed out of aquifers, for the fact that an inefficient car fleet takes ten to twenty years to turn over.
The possible exceptional leverage point here is in the size of stocks, or buffers. Consider a huge bathtub with slow in and outflows. Now think about a small one with fast flows. That's the difference between a lake and a river. You hear about catastrophic river floods much more often than catastrophic lake floods, because stocks that are big, relative to their flows, are more stable than small ones. A big, stabilizing stock is a buffer.
The stabilizing power of buffers is why you keep money in the bank rather than living from the flow of change through your pocket. It's why stores hold inventory instead of calling for new stock just as customers carry the old stock out the door. It's why we need to maintain more than the minimum breeding population of an endangered species. Soils in the eastern U.S. are more sensitive to acid rain than soils in the west, because they haven't got big buffers of calcium to neutralize acid. You can often stabilize a system by increasing the capacity of a buffer. But if a buffer is too big, the system gets inflexible. It reacts too slowly. Businesses invented just-in-time inventories, because occasional vulnerability to fluctuations or screw-ups is cheaper than certain, constant inventory costs—and because small-to-vanishing inventories allow more flexible response to shifting demand.
There's leverage, sometimes magical, in changing the size of buffers. But buffers are usually physical entities, not easy to change.
The acid absorption capacity of eastern soils is not a leverage point for alleviating acid rain damage. The storage capacity of a dam is literally cast in concrete. Physical structure is crucial in a system, but the leverage point is in proper design in the first place. After the structure is built, the leverage is in understanding its limitations and bottlenecks and refraining from fluctuations or expansions that strain its capacity.
Now we're beginning to move from the physical part of the system to the information and control parts, where more leverage can be found. Nature evolves negative feedback loops and humans invent them to keep system states within safe bounds.
A thermostat loop is the classic example. Its purpose is to keep the system state called "room temperature" fairly constant at a desired level. Any negative feedback loop needs a goal (the thermostat setting), a monitoring and signaling device to detect excursions from the goal (the thermostat), and a response mechanism (the furnace and/or air conditioner, fans, heat pipes, fuel, etc.).
A complex system usually has numerous negative feedback loops it can bring into play, so it can self-correct under different conditions and impacts. Some of those loops may be inactive much of the time—like the emergency cooling system in a nuclear power plant, or your ability to sweat or shiver to maintain your body temperature. One of the big mistakes we make is to strip away these emergency response mechanisms because they aren't often used and they appear to be costly. In the short term we see no effect from doing this. In the long term, we narrow the range of conditions over which the system can survive.
One of the most heartbreaking ways we do this is in encroaching on the habitats of endangered species. Another is in encroaching on our own time for rest, recreation, socialization, and meditation.
The "strength" of a negative loop—its ability to keep its appointed stock at or near its goal—depends on the combination of all its parameters and links—the accuracy and rapidity of monitoring, the quickness and power of response, the directness and size of corrective flows.
There can be leverage points here. Take markets, for example, the negative feedback systems that are all but worshiped by economists—and they can indeed be marvels of self-correction, as prices vary to keep supply and demand in balance. The more the price—the central signal to both producers and consumers—is kept clear, unambiguous, timely, and truthful, the more smoothly markets will operate. Prices that reflect full costs will tell consumers how much they can actually afford and will reward efficient producers. Companies and governments are fatally attracted to the price leverage point, of course, all of them pushing in the wrong direction with subsidies, fixes, externalities, taxes, and other forms of confusion. The REAL leverage here is to keep them from doing it. Hence antitrust laws, truth-in-advertising laws, attempts to internalize costs (such as pollution taxes), the removal of perverse subsidies, and other ways of leveling market playing fields.
The strength of a negative feedback loop is important RELATIVE TO THE IMPACT IT IS DESIGNED TO CORRECT. If the impact increases in strength, the feedbacks have to be strengthened too.
A thermostat system may work fine on a cold winter day—but open all the windows and its corrective power will fail. Democracy worked better before the advent of the brainwashing power of centralized mass communications. Traditional controls on fishing were sufficient until radar spotting and drift nets and other technologies made it possible for a few actors to wipe out the fish. The power of big industry calls for the power of big government to hold it in check; a global economy makes necessary a global government.
Here are some other examples of strengthening negative feedback controls to improve a system's self-correcting abilities: preventive medicine, exercise, and good nutrition to bolster the body's ability to fight disease, integrated pest management to encourage natural predators of crop pests, the Freedom of Information Act to reduce government secrecy, protection for whistleblowers, impact fees, pollution taxes, and performance bonds to recapture the externalized public costs of private benefits.
A positive feedback loop is self-reinforcing. The more it works, the more it gains power to work some more.
The more people catch the flu, the more they infect other people. The more babies are born, the more people grow up to have babies. The more money you have in the bank, the more interest you earn, the more money you have in the bank. The more the soil erodes, the less vegetation it can support, the fewer roots and leaves to soften rain and runoff, the more soil erodes. The more high-energy neutrons in the critical mass, the more they knock into nuclei and generate more.
Positive feedback loops drive growth, explosion, erosion, and collapse in systems. A system with an unchecked positive loop ultimately will destroy itself. That's why there are so few of them.
Usually a negative loop kicks in sooner or later. The epidemic runs out of infectable people—or people take increasingly strong steps to avoid being infected. The death rate rises to equal the birth rate—or people see the consequences of unchecked population growth and have fewer babies. The soil erodes away to bedrock, and after a million years the bedrock crumbles into new soil—or people put up check dams and plant trees.
In those examples, the first outcome is what happens if the positive loop runs its course, the second is what happens if there's an intervention to reduce its power.
Reducing the gain around a positive loop—slowing the growth—is usually a more powerful leverage point in systems than strengthening negative loops, and much preferable to letting the positive loop run.
Population and economic growth rates in the world model are leverage points, because slowing them gives the many negative loops, through technology and markets and other forms of adaptation, time to function. It's the same as slowing the car when you're driving too fast, rather than calling for more responsive brakes or technical advances in steering.
The most interesting behavior that rapidly turning positive loops can trigger is chaos. This wild, unpredictable, unreplicable, and yet bounded behavior happens when a system starts changing much, much faster than its negative loops can react to it.
For example, if you keep raising the capital growth rate in the world model, eventually you get to a point where one tiny increase more will shift the economy from exponential growth to oscillation. Another nudge upward gives the oscillation a double beat. And just the tiniest further nudge sends it into chaos.
I don't expect the world economy to turn chaotic any time soon (not for that reason, anyway). That behavior occurs only in unrealistic parameter ranges, equivalent to doubling the size of the economy within a year. Real-world systems do turn chaotic, however, if something in them can grow or decline very fast. Fast-replicating bacteria or insect populations, very infectious epidemics, wild speculative bubbles in money systems, neutron fluxes in the guts of nuclear power plants. These systems are hard to control, and control must involve slowing down the positive feedbacks.
In more ordinary systems, look for leverage points around birth rates, interest rates, erosion rates, "success to the successful" loops, any place where the more you have of something, the more you have the possibility of having more.
There was this subdivision of identical houses, the story goes, except that the electric meter in some of the houses was installed in the basement and in others it was installed in the front hall, where the residents could see it constantly, going round faster or slower as they used more or less electricity. Electricity consumption was 30 percent lower in the houses where the meter was in the front hall.
Systems-heads love that story because it's an example of a high leverage point in the information structure of the system. It's not a parameter adjustment, not a strengthening or weakening of an existing loop. It's a NEW LOOP, delivering feedback to a place where it wasn't going before.
In 1986 the U.S. government required that every factory releasing hazardous air pollutants report those emissions publicly. Suddenly everyone could find out precisely what was coming out of the smokestacks in town. There was no law against those emissions, no fines, no determination of "safe" levels, just information. But by 1990 emissions dropped 40 percent. One chemical company that found itself on the Top Ten Polluters list reduced its emissions by 90 percent, just to "get off that list."
Missing feedback is a common cause of system malfunction. Adding or rerouting information can be a powerful intervention, usually easier and cheaper than rebuilding physical structure.
The tragedy of the commons that is exhausting the world's commercial fisheries occurs because there is no feedback from the state of the fish population to the decision to invest in fishing vessels. (Contrary to economic opinion, the price of fish doesn't provide that feedback. As the fish get more scarce and hence more expensive, it becomes all the more profitable to go out and catch them. That's a perverse feedback, a positive loop that leads to collapse.)
It's important that the missing feedback be restored to the right place and in compelling form. It's not enough to inform all the users of an aquifer that the groundwater level is dropping. That could trigger a race to the bottom. It would be more effective to set a water price that rises steeply as the pumping rate exceeds the recharge rate.
Suppose taxpayers got to specify on their return forms what government services their tax payments must be spent on. (Radical democracy!) Suppose any town or company that puts a water intake pipe in a river had to put it immediately DOWNSTREAM from its own outflow pipe. Suppose any public or private official who made the decision to invest in a nuclear power plant got the waste from that plant stored on his/her lawn.
There is a systematic tendency on the part of human beings to avoid accountability for their own decisions. That's why there are so many missing feedback loops—and why this kind of leverage point is so often popular with the masses, unpopular with the powers that be, and effective, if you can get the powers that be to permit it to happen or go around them and make it happen anyway.
The rules of the system define its scope, boundaries, degrees of freedom. Thou shalt not kill. Everyone has the right of free speech. Contracts are to be honored. The president serves four-year terms and cannot serve more than two of them. Nine people on a team, you have to touch every base, three strikes and you're out. If you get caught robbing a bank, you go to jail.
Mikhail Gorbachev came to power in the USSR and opened information flows (glasnost) and changed the economic rules (perestroika), and look what happened.
Constitutions are strong social rules. Physical laws such as the second law of thermodynamics are absolute rules, if we understand them correctly. Laws, punishments, incentives, and informal social agreements are progressively weaker rules.
To demonstrate the power of rules, I ask my students to imagine different ones for a college. Suppose the students graded the teachers. Suppose you come to college when you want to learn something, and you leave when you've learned it. Suppose professors were hired according to their ability to solve real-world problems, rather than to publish academic papers. Suppose a class got graded as a group, instead of as individuals.
Rules change behavior. Power over rules is real power.
That's why lobbyists congregate when Congress writes laws, and why the Supreme Court, which interprets and delineates the Constitution—the rules for writing the rules—has even more power than Congress.
If you want to understand the deepest malfunctions of systems, pay attention to the rules, and to who has power over them.
That's why my systems intuition was sending off alarm bells as the new world trade system was explained to me. It is a system with rules designed by corporations, run by corporations, for the benefit of corporations. Its rules exclude almost any feedback from other sectors of society. Most of its meetings are closed to the press (no information, no feedback). It forces nations into positive loops, competing with each other to weaken environmental and social safeguards in order to attract corporate investment. It's a recipe for unleashing "success to the successful" loops.
The most stunning thing living systems can do is to change themselves utterly by creating whole new structures and behaviors. In biological systems that power is called evolution. In human economies it's called technical advance or social revolution. In systems lingo it's called self-organization.
Self-organization means changing any aspect of a system lower on this list—adding or deleting new physical structure, adding or deleting negative or positive loops or information flows or rules. The ability to self-organize is the strongest form of system resilience, the ability to survive change by changing.
The human immune system can develop responses to (some kinds of) insults it has never before encountered. The human brain can take in new information and pop out completely new thoughts.
Self-organization seems so wondrous that we tend to regard it as mysterious, miraculous. Economists often model technology as literal manna from heaven—coming from nowhere, costing nothing, increasing the productivity of an economy by some steady percent each year. For centuries people have regarded the spectacular variety of nature with the same awe. Only a divine creator could bring forth such a creation.
In fact the divine creator does not have to produce miracles. He, she, or it just has to write clever RULES FOR SELF-ORGANIZATION. These rules govern how, where, and what the system can add onto or subtract from itself under what conditions.
Self-organizing computer models demonstrate that delightful, mind-boggling patterns can evolve from simple evolutionary algorithms. (That need not mean that real-world algorithms are simple, only that they can be.) The genetic code that is the basis of all biological evolution contains just four letters, combined into words of three letters each. That code, and the rules for replicating and rearranging it, has spewed out an unimaginable variety of creatures.
Self-organization is basically a matter of evolutionary raw material—a stock of information from which to select possible patterns—and a means for testing them. For biological evolution the raw material is DNA, one source of variety is spontaneous mutation, and the testing mechanism is something like punctuated Darwinian selection. For technology the raw material is the body of understanding science has accumulated. The source of variety is human creativity (whatever THAT is) and the selection mechanism is whatever the market will reward or whatever governments and foundations will fund or whatever tickles the fancy of crazy inventors.
When you understand the power of self-organization, you begin to understand why biologists worship biodiversity even more than economists worship technology. The wildly varied stock of DNA, evolved and accumulated over billions of years, is the source of evolutionary potential, just as science libraries and labs and scientists are the source of technological potential. Allowing species to go extinct is a systems crime, just as randomly eliminating all copies of particular science journals, or particular kinds of scientists, would be.
The same could be said of human cultures, which are the store of behavioral repertoires accumulated over not billions, but hundreds of thousands of years. They are a stock out of which social evolution can arise. Unfortunately, people appreciate the evolutionary potential of cultures even less than they understand the potential of every genetic variation in ground squirrels. I guess that's because one aspect of almost every culture is a belief in the utter superiority of that culture.
Any system, biological, economic, or social, that scorns experimentation and wipes out the raw material of innovation is doomed over the long term on this highly variable planet.
The intervention point here is obvious but unpopular. Encouraging diversity means losing control. Let a thousand flowers bloom and ANYTHING could happen!
Who wants that?
Right there, the push for control, is an example of why the goal of a system is even more of a leverage point than the self-organizing ability of a system.
If the goal is to bring more and more of the world under the control of one central planning system (the empire of Genghis Khan, the world of Islam, the People's Republic of China, Wal-Mart, Disney), then everything further down the list, even self-organizing behavior, will be pressured or weakened to conform to that goal.
That's why I can't get into arguments about whether genetic engineering is a good or a bad thing. Like all technologies, it depends upon who is wielding it, with what goal. The only thing one can say is that if corporations wield it for the purpose of generating marketable products, that is a very different goal, a different direction for evolution than anything the planet has seen so far.
There is a hierarchy of goals in systems. Most negative feedback loops have their own goals—to keep the bath water at the right level, to keep the room temperature comfortable, to keep inventories stocked at sufficient levels. They are small leverage points. The big leverage points are the goals of entire systems.
People within systems don't often recognize what whole-system goal they are serving. To make profits, most corporations would say, but that's just a rule, a necessary condition to stay in the game. What is the point of the game? To grow, to increase market share, to bring the world (customers, suppliers, regulators) more under the control of the corporation, so that its operations become ever more shielded from uncertainty. That's the goal of a cancer cell too and of every living population. It's only a bad one when it isn't countered by higher-level negative feedback loops with goals of keeping the system in balance. The goal of keeping the market competitive has to trump the goal of each corporation to eliminate its competitors. The goal of keeping populations in balance and evolving has to trump the goal of each population to commandeer all resources into its own metabolism.
I said a while back that changing the players in a system is a low-level intervention, as long as the players fit into the same old system. The exception to that rule is at the top, if a single player can change the system's goal.
I have watched in wonder as—only very occasionally—a new leader in an organization, from Dartmouth College to Nazi Germany, comes in, enunciates a new goal, and single-handedly changes the behavior of hundreds or thousands or millions of perfectly rational people.
That's what Ronald Reagan did. Not long before he came to office, a president could say, "Ask not what government can do for you, ask what you can do for the government," and no one even laughed. Reagan said the goal is not to get the people to help the government and not to get government to help the people, but to get the government off our backs. One can argue, and I would, that larger system changes let him get away with that. But the thoroughness with which behavior in the U.S. and even the world has been changed since Reagan is testimony to the high leverage of articulating, repeating, standing for, insisting upon new system goals.
Another of Jay Forrester's systems sayings goes: It doesn't matter how the tax law of a country is written. There is a shared idea in the minds of the society about what a "fair" distribution of the tax load is. Whatever the rules say, by fair means or foul, by complications, cheating, exemptions or deductions, by constant sniping at the rules, the actual distribution of taxes will push right up against the accepted idea of "fairness."
The shared idea in the minds of society, the great unstated assumptions—unstated because unnecessary to state; everyone knows them—constitute that society's deepest set of beliefs about how the world works. There is a difference between nouns and verbs. People who are paid less are worth less. Growth is good. Nature is a stock of resources to be converted to human purposes. Evolution stopped with the emergence of Homo sapiens. One can "own" land. Those are just a few of the paradigmatic assumptions of our culture, all of which utterly dumbfound people of other cultures.
Paradigms are the sources of systems. From them come goals, information flows, feedbacks, stocks, flows.
The ancient Egyptians built pyramids because they believed in an afterlife. We build skyscrapers, because we believe that space in downtown cities is enormously valuable. (Except for blighted spaces, often near the skyscrapers, which we believe are worthless.) Whether it was Copernicus and Kepler showing that the earth is not the center of the universe, or Einstein hypothesizing that matter and energy are interchangeable, or Adam Smith postulating that the selfish actions of individual players in markets wonderfully accumulate to the common good.
People who manage to intervene in systems at the level of paradigm hit a leverage point that totally transforms systems.
You could say paradigms are harder to change than anything else about a system, and therefore this item should be lowest on the list, not the highest. But there's nothing physical or expensive or even slow about paradigm change. In a single individual it can happen in a millisecond. All it takes is a click in the mind, a new way of seeing. Of course individuals and societies do resist challenges to their paradigm harder than they resist any other kind of change.
So how do you change paradigms? Thomas Kuhn, who wrote the seminal book about the great paradigm shifts of science, has a lot to say about that. In a nutshell, you keep pointing at the anomalies and failures in the old paradigm, you come yourself, loudly, with assurance, from the new one, you insert people with the new paradigm in places of public visibility and power. You don't waste time with reactionaries; rather you work with active change agents and with the vast middle ground of people who are open-minded.
Systems folks would say one way to change a paradigm is to model a system, which takes you outside the system and forces you to see it whole. We say that because our own paradigms have been changed that way.
0. The power to transcend paradigms.
Sorry, but to be truthful and complete, I have to add this kicker.
The highest leverage of all is to keep oneself unattached in the arena of paradigms, to realize that NO paradigm is "true," that even the one that sweetly shapes one's comfortable worldview is a tremendously limited understanding of an immense and amazing universe.
It is to "get" at a gut level the paradigm that there are paradigms, and to see that that itself is a paradigm, and to regard that whole realization as devastatingly funny. It is to let go into Not Knowing.
People who cling to paradigms (just about all of us) take one look at the spacious possibility that everything we think is guaranteed to be nonsense and pedal rapidly in the opposite direction. Surely there is no power, no control, not even a reason for being, much less acting, in the experience that there is no certainty in any worldview. But everyone who has managed to entertain that idea, for a moment or for a lifetime, has found it a basis for radical empowerment. If no paradigm is right, you can choose one that will help achieve your purpose. If you have no idea where to get a purpose, you can listen to the universe (or put in the name of your favorite deity here) and do his, her, its will, which is a lot better informed than your will.
It is in the space of mastery over paradigms that people throw off addictions, live in constant joy, bring down empires, get locked up or burned at the stake or crucified or shot, and have impacts that last for millennia.
Back from the sublime to the ridiculous, from enlightenment to caveats. There is so much that has to be said to qualify this list. It is tentative and its order is slithery. There are exceptions to every item on it. Having the list percolating in my subconscious for years has not transformed me into a Superwoman. I seem to spend my time running up and down the list, trying out leverage points wherever I can find them. The higher the leverage point, the more the system resists changing it—that's why societies rub out truly enlightened beings.
I don't think there are cheap tickets to system change. You have to work at it, whether that means rigorously analyzing a system or rigorously casting off paradigms. In the end, it seems that leverage has less to do with pushing levers than it does with disciplined thinking combined with strategically, profoundly, madly letting go.
Donella Meadows is an ecologist and founder of the Donella Meadows Institute who died suddenly of meningitis on February 20, 2001. Meadows wrote extensively about economic systems and sustainability, and wrote and worked tirelessly on behalf of the Earth.
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text:
import * as React from 'react'
import {Link} from 'react-router-dom'
import {connect} from 'react-redux'

import * as messages from '../messages'
import * as user from '../user'
import * as events from '../events'
import * as bookings from '../bookings'

import {withRouter} from 'react-router-dom';
import {matchPath}  from 'react-router'

import {
    Container,
    Row,
    Col
} from 'reactstrap';

class App extends React.Component<any, any> {

    constructor(props) {
        super(props);
    }

    componentWillMount() {
        this.props.getUser();
        this.props.getEvents();
        this.props.getUserBookings();
    }

    componentWillReceiveProps(nextProps) { //refresh bookings/events if we log in/out
        if (this.props.User !== null && this.props.User !== nextProps.User) {
            this.props.getUserBookings();
            this.props.getEvents(); //need to drop the detailed event models if present
        }
    }

    render() {

        //prevent render until we have the basic data available, this makes child components much simpler.
        if (this.props.User === null || this.props.Events === null || this.props.Bookings === null) return (

);

        const envMarker = this.props.Env === 'dev' ?

TEST

 : null;

        const inManage = !!matchPath(location.pathname, {
            path:   "/event/:eventId/manage",
            exact:  false,
            strict: false
        });

        return (
            <React.Fragment>
                {envMarker}
                <Container fluid={inManage}>
                    <Row className="align-items-center">
                        <Col>

{window.location.hostname}

                        </Col>
                        <Col sm="auto">

                        </Col>
                    </Row>
                    <Row>
                        <Col>
                            <Link to="/">Home</Link>
                        </Col>
                        <Col sm="auto">
                            <user.loginStatus/>
                        </Col>
                    </Row>
                    <Row>
                        <messages.messages/>
                    </Row>
                    {this.props.children}
                    <Row>
                        <Col>

© 2018 Woodcraft
                                Folk, Source on Github.

                        </Col>
                    </Row>
                </Container>
            </React.Fragment>
        );
    }
}

//store.dispatch(user.actions.getUser());

const mapStateToProps = (state) => {
    let User = state.getIn(["User", "user"]);
    let Events = state.getIn(["Events", "events"]);
    let Bookings = state.getIn(["Bookings", "bookings"]);
    let Env = state.get("App");
    return {User, Events, Bookings, Env};
};

const mapDispatchToProps = {
    getUser: user.actions.getUser,
    getEvents: events.actions.getEvents,
    getUserBookings: bookings.actions.getUserBookings
};

var VisibleApp = connect(
    mapStateToProps,
    mapDispatchToProps
)(App);

export default withRouter(VisibleApp);

redpajama_set_name: RedPajamaGithub


All wagons numbered in the private owner series carry a prefix to indicate their ownership. A list of all known codes is given below. Note that some codes were issued but not actually used on any wagons, particularly in the case of RIV wagons. Codes are not re-used; where two or more names are given, this is due to the company having been taken over or re-named. Codes in italic are those carried by privately-owned coaching stock during the time when such vehicles were assigned PO numbers. Not all the coach ownership codes may be included as some were only registered for a short period. Codes in bold were still in use as of late 2006.
EWS 2006- English Welsh and Scottish Railway Only appears on TEA tanks numbered in railway-owned series.
PDS 1990-? Powell Duffryn Standard Only carried by PDS28100?


text:
Fire Escape Collapse Pulitzer Prize Winning Photographs
click here to purchase images
The Story Behind the Photos
Written in 1975, By Stanley Forman
Except for the tragedy itself, the whole experience has been fantastic. Other newsmen will know what I mean, even if a lot of crank letter writers do not.
For nine years as a photographer with the Hearst papers in Boston, I would look at some fantastic news shot and day dream about when I would do it.
Now that I've taken a shot that has gotten world-wide recognition, the most frightening thing is the guys in the office who say I've reached my peak at age 30, that I'll never do it again. I hope they're wrong.
Meanwhile the after effects of the fire escape pictures have been just about the way I dreamed it would be. Both AP and UPI made it a point to get me tear sheets of papers around the World and combined with those that have been sent by other photographers, editors and just nice people, there are more than 200 so far, from Australia to Paris, Honolulu to Bangor.
Lou Garcia, formerly with the AP in Paris and now with UPI in Paris, sent me the French papers, but the only words I could understand were my name. The European papers really use a lot of pictures though.
There's been a lot of mail; some of it critical from people who I don't think know why newspapers exist. But there's also been a lot of positive mail, especially from fire departments and other public safety agencies who want to study the pictures or post them as a warning to their departments. There have even been letters and calls from guys I went to school with and haven't seen in 10 years.
Both wire services were generous financially, even though they didn't have to be. And my office gave me a bonus the next day and a raise just this month.
The pictures have already won the NPPA clip contest and the Herald American monthly in-house contest. I also go a plaque from the School of Modern Photography. I'm looking forward to the yearend contests. But I cringe a little every time I see another good shot or some nut aims a gun at President Ford. I keep remembering there's still three months left in 1975.
Win or lose though, at least I'm no longer remembered only as the photographer who got beaten up by the women at Harvard. (And anyway I didn't get beaten up).
Andre Kenner - After 35 Years, Fire Escape Collapse
© 2022 www.stanleyformanphotos.com

redpajama_set_name: RedPajamaCommonCrawl


text:
Katy Perry Shares Sweet Never-Before-Seen Photos with Fiancé Orlando Bloom on His 44th Birthday
"So glad my moon found it's sun, love you whole world doe," the singer wrote of Orlando Bloom
Katy Perry Says Sleep Has Been a 'Challenge' Since Welcoming Daughter Daisy Dove: 'Where Did It Go?'
The singer welcomed her first child — daughter Daisy Dove — with fiancé Orlando Bloom in August
Miranda Kerr shares secret to co-parenting with Orlando Bloom and Katy Perry: 'We all really respect each other'
The former Victoria's Secret model has nothing but love for the pop star. "I adore Katy."
Katy Perry Uses a Breast Pump in Jane Fonda Workout Video to Encourage Getting 'Pumped to Vote'
"Whoever said pumping isn't a sport ... I'd like to twist their nipples clockwise for one week straight," Katy Perry joked alongside the video
Katy Perry shares candid motherhood selfie days after giving birth: 'Hair n makeup by exhaustion'
The new mom gives followers a look into her first days with baby Daisy.
Katy Perry and Orlando Bloom Welcome Daughter Daisy Dove: 'We Are Floating with Love'
The new addition is the first child for Katy Perry and second for Orlando Bloom, who also shares 9½-year-old son Flynn with ex-wife Miranda Kerr
The It List: Dev Patel is David Copperfield in Armando Iannucci's new film, Tyler Perry's Madea takes her final bow, Katy Perry drops 'Smile' and the best in pop culture the week of Aug. 24, 2020
Here are our pop culture picks for Aug. 24-30, including the best deals we could find for each.
Katy Perry Jokes About How Pregnancy Lasts for '10+ Months' as She Awaits Daughter's Birth
Katy Perry and fiancé Orlando Bloom are expecting their first child, a daughter
Sofia Vergara defends relationship with Ellen DeGeneres after old videos emerge: 'I was never a victim'
Sofia Vergara clarified that her relationship with Ellen DeGeneres is based on humor, after old videos showed the talk show host mocking her accent.
Katy Perry, Luke Bryan, Lionel Richie Back as American Idol Judges for Show's Fourth Season on ABC
Ryan Seacrest will also return to host the singing competition series
Pregnant Katy Perry Shares First Look at Her Baby Girl's Nursery and Adorable Orlando Bloom Onesie
Katy Perry is gearing up to welcome her first child, a daughter, with fiancé Orlando Bloom
Katy Perry turned to Sia during dark time: 'She had a real breakdown'
Perry met Sia in 2014, and they bonded over their struggles with mental health issues.
Pregnant Katy Perry Shows Off Bare Baby Bump Dancing Outside of Car to Viral Song
The "Smile" singer is expecting her first child — a girl — with fiancé Orlando Bloom
18 Celebs Who Have Clapped Back at Ellen DeGeneres, From Playful Ribbing to Genuine Disdain (Photos)
Sean Hayes: In a spontaneous game of "The Battle of the Gays," DeGeneres and the "Will & Grace" star one-up'd each other with digs about the other's career. It began with Hayes calling DeGeneres "Helen," while applauding that her talk show has been on-air for 15 years. "I've also done other things in the past," she smiled. Segueing into talking about "Will & Grace," she asked, "How long was it [on-air] the first time around… before y'all got canceled?" He picked up his mug and, looking pensive, answered, "I think it was longer than your sitcom was." But DeGeneres won the round, adding, "Yeah, that's right. I had to come out first for y'all do that sitcom."Dakota Johnson: When DeGeneres asked the "Fifty Shades of Grey" actress why she wasn't invited to her celeb-studded 30th birthday party, Johnson said, "Actually no. That's not the truth, Ellen. You were invited… Last time I was on the show last year, you gave me a bunch of s— about not inviting you, but I didn't even know you wanted to be invited. I didn't even know you liked me!" Caught off guard, DeGeneres insisted, "Of course I like you," followed by some rather awkward silence. It only got worse when DeGeneres asked about comedian Tig Notaro performing at the party. Johnson responded, "She's my favorite comedian…other than you!"Michelle Obama: The former first lady proved she has a great sense of humor when she appeared on "Ellen" and gifted here with a bottle of Metamucil, saying, "something to keep you flowing." Before the Obamas moved out of the White House, DeGeneres took her to CVS, to show her how to survive a normal lifestyle. There, Obama was challenged by the comedian's behavior that included opening packages, eating food without paying for it, announcing to the store that Obama had "a rash" and singing through a megaphone to a sleeping baby. Finally, Obama said, "Ya know, you're really annoying. It's like taking a 3-year-old to the store."Katy Perry: DeGeneres had another memory lapse when she forgot that the "Smile" singer had been married to actor Russell Brand. Perry looked surprised when the host asked, "Were you [married]?" Perry whispered, "His name was Russell Brand. Remember, you gave me some wedding gifts on this show?" Perry smiled into the camera and mimed scissors, as if she was cutting the exchange. On the flip side, Perry is one of the few celebrities who has defended DeGeneres in recent weeks. "I think we all have witnessed the light and continual fight for equality that she has brought on the world through her platform for decades. Sending you love and a hug, friend Ellen," Perry tweeted.Justin Timberlake: In a 2016 appearance on "Ellen," Timberlake joked about her tequila-influenced flub of the lyrics to his song, "Can't Stop the Feeling." She, apparently, loves that song, and after having a little too much of Timberlake's brand of tequila with friends, she was recorded singing and dancing to it, but messing up the lyrics in the process. Timberlake said she sang the line, "Just electric, just electric, just electric" when, he said, "It pretty clearly says 'just imagine.'" Appearing to be a little embarrassed, DeGeneres asked the audience to back her up. "I don't think anyone raised their hand," he grinned.Hasan Minhaj: Within a minute of sitting down with DeGeneres, the stand-up comedian and political commentator best known for his Netflix show "Patriot Act" corrected her pronunciation of his name. "At Starbucks, I just go by Timothée Chalamet," he said.Blake Shelton: When "The Voice" judge appeared on "Ellen," she told the story of how she gave Jennifer Lopez a clock with a photo of her and A-Rod kissing on it, so she could remind him "the clock is ticking, time is passing," as an incentive for them to get engaged. And a week later he proposed. Well, DeGeneres gave Shelton a similar clock with him and Gwen Stefani on it. But it turned out that she didn't give it to Shelton after all. "I walked backstage and somebody back there was, like, 'Hey, thanks for being on the show. Can I have that?' and they took it." He joked that, whoever her next guest is, the show will just "replace the picture and do the same crap to them."Giada De Laurentiis: In a cooking segment on "Ellen," the Food Network's popular chef was trying to show DeGeneres and Nicole Kidman how to make arancini balls — an Italian snack of risotto coated in flour, bread crumbs and then fried — and innuendos started to fly. When DeGeneres questioned how to roll it into a ball, De Laurentiis replied, "Haven't you made any… kind of… balls… before?" stuttering as she realized how it sounded as she was saying it. DeGeneres grinned and shook her head no, causing the audience to burst into laughter. The host's culinary skills didn't get much better, which De Laurentiis pointed out. Looking at the mixture in DeGeneres' hand, she said, "That looks like dog food now."Wendy Williams: The two daytime talk show queens had a bit of a clash in 2013 when Williams first appeared on "Ellen," when the comedian called her mean and asked if she had ever gotten in trouble by speaking badly about other celebs. DeGeneres then invited her to a game of Heads Up, in which Willaims is shown the name of someone and has to describe them in hopes of DeGeneres figuring out who it is. When Justin Bieber's name popped up, Williams' clue included, "Some people say that he looks like you." DeGeneres looked puzzled. Williams defended herself, asking the crowd, "I've heard that! You've never heard that?!" DeGeneres laughed it off.Justin Bieber: DeGeneres put the "Yummy" singer on the spot when she interrogated him about a paparazzi photo that showed him naked on the balcony of a Bora Bora hotel, with a female seen sitting inside. She asked him who the girl was, and he said she was just a friend and they weren't dating. DeGeneres pressed, "You just brought a friend to Bora Bora? And you're just naked with your friend?" Bieber covered his face with his hands, saying, "Why are you putting me on the spot like this?" But she relented, "Wow. I have friends, I've never seen them naked like that. And they don't bring me to Bora Bora." Bieber responded, "Stop. You're making me blush, dude."Taylor Swift: The "Cardigan" singer's love life is frequently the topic of the tabloid, and DeGeneres pretty much jumped on that bandwagon during one stop Swift made on the show. DeGeneres asked who her 2012 song "We Are Never Ever Getting Back Together" was about. When Swift declined to answer, the host put up a series of photos of Swift with different guys, handed her a bell and said if the guy was someone she dated, ring the bell. Photos of Swift with everyone from John Mayer to Danny DeVito popped up, prompting Swift to beg that DeGeneres stop. "This makes me feel so bad about myself," she said. "Every time I come up here, you put like a different dude up there on the screen, and it just really makes me question what I stand for as a human being."Mark Ruffalo: A photo of DeGeneres attending a football game with former president George W. Bush and her defense of their friendship started a firestorm on social media. "Just because I don't agree with someone on everything doesn't mean I'm not going to be friends with them," she said. But Mark Ruffalo (and Susan Sarandon) took exception to her justification. "Sorry, until George W. Bush is brought to justice for the crimes of the Iraq War, (including American-lead torture, Iraqi deaths & displacement, and the deep scars–emotional & otherwise–inflicted on our military that served his folly), we can't even begin to talk about kindness," Ruffalo tweeted.Piers Morgan: Another photo got DeGeneres in hot water, this one was of the talk show host wishing Katy Perry happy birthday by tweeting a picture of herself appearing to ogle Perry's breasts. The caption to the photo read, "Happy birthday, @KatyPerry! It's time to bring out the big balloons!" Many, including Morgan, accused her of making a sexist joke. "If a man made this joke, Ellen would lead the cries of 'SEXIST PIG!'" Morgan wrote.NikkieTutorials: The makeup artist, YouTube celebrity and beauty influencer said on the Dutch talk show "De Wereld Draait Door" that her experience as a guest on "The Ellen Show" was not a pleasant one. She said she was "greeted by an angry intern who was a bit overworked," adding, "I was expecting a Disney show but got 'Teletubbies After Dark.'" She went on to say, "Every guest at 'Ellen's' had a private toilet, but I didn't. I was not allowed to use the nearest toilet because it was reserved for the Jonas Brothers."Kathy Griffin: The outspoken comedian got defensive when DeGeneres decided against paying tribute to Joan Rivers after her death because she thought Rivers' humor was mean-spirited. Griffin, in turn, called DeGeneres an untalented hack. In her book, "Kathy Griffin's Celebrity Run-Ins: My A-Z Index," Griffin wrote, "I'm almost positive a certain beloved daytime talk show host once had me kicked out of a backstage dressing room at the Emmy Awards. I can't prove it, but this person, who has short blonde hair, has a mean streak that all of Hollywood knows about."Brad Garrett: As rumblings of a toxic workplace environment behind-the-scenes on "The Ellen Show" surfaced and after DeGeneres made a public apology, the "Everybody Loves Raymond" actor spoke out about his experience as a guest on her show. "Sorry but it comes from the top @TheEllenShow," Garrett tweeted. "Know more than one who were treated horribly by her. Common knowledge."Lea Thompson: The "Back to the Future" actress backed Garrett's assessment of the environment at the talk show and that DeGeneres herself was the cause of it. Responding to Garrett's tweet, Thompson replied simply, "True story. It is."Kevin T. Porter: Comedian Kevin T. Porter put his money where his mouth is when it comes to disdain he has for DeGeneres. He tweeted, "Right now we all need a little kindness. You know, like Ellen Degeneres always talks about! She's also notoriously one of the meanest people alive Respond to this with the most insane stories you've heard about Ellen being mean & I'll match every one w/ $2 to @LAFoodBank."Read original story 18 Celebs Who Have Clapped Back at Ellen DeGeneres, From Playful Ribbing to Genuine Disdain (Photos) At TheWrap
Kevin Hart publicly supports Ellen DeGeneres as criticism grows: She's shown me 'love and respect from day 1'
Kevin Hart is showing his support for Ellen DeGeneres amid the scandal surrounding her daytime talk show.
Katy Perry reveals she had suicidal thoughts in 2017: 'I just crashed'
Katy Perry says her mental health was in a very bad place in 2017.
Katy Perry says she 'became very upset and clinically depressed' after last album performed poorly
Katy Perry's mental health suffered after she was disappointed by the reception to her album "Witness."
Pregnant Katy Perry strips down in idyllic 'Daisies' music video
Perry's profile pose is reminiscent of other iconic au naturel maternity shots, like Demi Moore and Serena Williams's famous Vanity Fair covers.
Katy Perry, John Legend, Christina Aguilera, DWTS Pros and More Join Disney Family Singalong 2
The Disney Family Singalong: Volume II airs on Sunday, May 10
Katy Perry Shares a Photo of the Madonna-Inspired Look She Would Have Worn to the Met Gala
Katy Perry gave fans a sneak peek at the ensemble that she was planning to wear the 2020 Met Gala, revealing that she was going to pay homage to Madonna. See the stunning look here.
Katy Perry Mourns the Death of Her Cat Kitty Purry: 'Thanks for the Cuddles and Companionship'
"I hope she rests in salmon fillets and tuna tartare way up in catnip heaven," Katy Perry wrote in a touching tribute to her late cat
Katy Perry and Orlando Bloom are expecting a baby girl
Katy Perry had been hoping for a girl all along, she told fans at a March concert.
Pregnant Katy Perry Shares Makeup-Free Selfie While Self-Isolating: 'Blackheads and All Baby'
"Hope your stay-at-home plans tonight include joining me for a beautiful and breezy episode of AmericanIdol" the singer wrote on Instagram
Katy Perry Wins Appeal in 'Dark Horse' Infringement Case
Judge reverses previous $2.8 million decision in favor of Christian rapper Flame
Katy Perry, Madonna duped by balcony videos from Italy's coronavirus lockdown
Celebrities are falling for doctored videos of Italians singing their songs during coronavirus lockdown.
Barb & Star Go to Vista Del Mar
F9: Fast And Furious 9
The Addams Family 2


text:
Aintree Grand National 2011
site map jockey ----------- Home Page ----------- Latest News ----------- Accessories Associations Bloodstock Agents Betting Exchanges Betting Strategy Bookmakers Cheltenham Festival Epsom Derby Equine Art & Gifts Fun and Games Grand National Horses Hospitality & Tickets Information Jockeys Laying Horses Links Sites Overseas Odds Comparison Portals Punchestown Racecourses Racing News Royal Ascot Sales Software Studs Syndicates Trainers ----------- Submit Site
grand national 2011 /
John Smith's Grand National Legends – Shortlist Announced
John Smith's and Aintree have announced their shortlist of ten 'Legends' aiming to be inducted into the John Smith's Grand National Legends.
www.grandnationallegends.com
The Legends was launched last year and celebrates the greats from Grand National history with Ginger McCain, Jenny Pitman and Sir Peter O'Sullevan among the first inductees in 2010.
This year's shortlist was compiled by a selection panel of racing experts who were asked to consider the star performers – equine and human – from the 1830s through to the present day. A website has been developed to allow the public to choose the identity of the 2011 Legends and this is now live and open for voting. The five Legends selected by public vote will be invited to Aintree racecourse on Grand National Day – Saturday 9th April.
Go to www.grandnationallegends.com to vote now.
The 2011 contenders are as follows:
Fred Rimell
Brian Fletcher
Vincent O'Brien
Fred Winter
Bob Champion and Aldaniti
Tommy Carberry
West Tip
Tim Forster
Duke of Alburquerque
Richard Dunwoody
Aintree and John Smith's are also searching for Grand National 'People's Legends' and are inviting local communities to nominate people and pubs that make their own contribution to the John Smith's Grand National? The best five nominations will be invited to Aintree on Liverpool Day, Thursday 7th April for a presentation ceremony as they join the John Smith's Grand National People's Legends.
Grand National winning jockey, Mick Fitzgerald was part of the selection committee:
"The John Smith's Grand National Legends was one of the highlights of last year's National meeting and it was fantastic to see Ginger McCain and Jenny Pitman alongside the People's Legends, like Liverpudlian Edie Roche. The great race always seems to throw up interesting stories and I'm looking forward to see how the public vote and who they nominate."
Voting for the John Smith's Grand National Legends closes on March 20 and voters will automatically be entered into a draw to win a VIP trip to Aintree and the chance to meet some of the Grand National Legends at the John Smith's Grand National on Saturday 9th April.
home | associations | bloodstock agents | bookmakers | links | information | jockeys | portals | racecourses | race horse trainers | sales | studs | syndicates | submit site


text:
DEMOCRATIC GOVERNANCE AND RULE OF LAW
WOMEN'S RIGHTS AND BODILY INTEGRITY
ECONOMIC JUSTICE AND CLIMATE GOVERNANCE PROGRAM
Clean Water, Sanitation and Hygiene (WASH)
Education and Life Skills Enhancement
NEWS AND INFORMATION RESOURCES
Citizens in Action Southern Africa
Protect, Develop and Empower
info@ciasouthernafrica.org
Headquarters Office 2nd Floor ,Msasa Windsor House Herbet Chitepo St Mutare, Zimbabwe
+263773323470Phone Number
The organization has been established by a group of women activists coming together in recognition and belief that the organization can make a significant and positive impact in Southern Africa and beyond the region. The CIASA formation was therefore meant to tackle important issues at a scale where it can achieve significant and measurable impacts. The organizations ability to take risks and make long-term and relatively large commitments should allow it to undertake challenges not accessible to many other organizations. This is against the realization that marginalized women and girls are being left behind in the development discourse of several Southern African countries.
CIASA seeks durable change, thus CIASA, is a specialized organization which was established as one of the major outcomes of the baseline, needs assessment and research conducted across Southern Africa. The research was organized in response to the solidarity and movement building crisis ailing countries in addressing national crisis especially around lack of proper democratic and economic governance, barriers in accessing comprehensive SRHR integrated with Sexual Gender Based Violence (SGBV) and women exclusion in natural resources governance in the turn of the millennium that primarily affected countries in Southern Africa. The research recommended that an organization should be established immediately to providing training oversight and think tanking around women and girl child related interest to climate change implications, child protection, environmental sustainability and democratic and economic governance.
Most low income developing countries in Southern Africa are characterised with low living standards which is threatening social harmony for women especially those in hard to reach areas. Despite the global efforts to end poverty through the Sustainable Development Goals, living standards have gotten worse for many women in African countries. For instance in Zimbabwe, the breadbasket has increased against extreme poverty for women despite the fact that the country is well endowed with natural resources such as minerals, and fertile land. The rich are getting richer given the opaqueness of the economy and the economic privileges created by political patronage. Worse still, inequalities on income and access to social services has been widened by Covid-19 with those poor not accessing such services as SRHR and education for a girl child, leaving the women and children vulnerable. Differential access to natural resources has widened the disparity between the elites and those who are wallowing in deep poverty with women being the most vulnerable groups. Zimbabwe amongst other African countries is now characterised by perennial labour disputes and industrial actions due to concerns over the welfare of the public service labour force which is largely constituted by women. From a feminist perspective, the provision of water, sanitation, health, education and other social services remain significantly poor, making it difficult for women to perform their caregiving role.
Exacerbated by COVID19 pandemic, poverty remains a daunting challenge in many African countries despite the fact that poverty reduction is at the priority list in national, continental and global development plans. Over the past decade, poverty levels are at unprecedented levels with urban poverty now widespread. Access to basic social services such as water and sanitation, health and education have turned out from being a right into a privilege in both rural and urban areas. The organization is a non-political and non-profit making non-governmental organization formed by young women activities with particular focus on marginalized women and girl child. This movement targets marginalized women and girls as heterogenous groups, in lobby and advocacy; influencing the policies as it relates to the rights of women and girls in their diversity and advance the rights-based approach to women and girl child development through well-thought citizens driven and led constitutional reforms premised under the pinnacles of transparency, accountability and good governance. The Citizen in Action Southern Africa is there to create and facilitate space for marginalized women and girls to have a collective voice to challenge oppressive systems and structural barriers and in turn effectively participate in key decision-making processes across the cultural, political, social, environmental, technological and economic spectrum.


text:
Q: Char pointer storing address of int type data Experts here I want to know that what's actually happening in this program. Because here the pointer is of char type and var1 is of integer type.
#include<stdio.h>
void main()
{
    char *ptr;
    int var1;
    ptr=&var1;
    *ptr=495;
    printf("\n%d %c",var1,var1);
    *ptr='495';
    printf("\n%d %c",var1,var1);
}

When I tried running this program, these are the warnings that I got-
v.c:6:4: warning: assignment from incompatible pointer type [-Wincompatible-pointer-types]
 ptr=&var1;
    ^
v.c:7:6: warning: overflow in implicit constant conversion [-Woverflow]
 *ptr=495;
      ^
v.c:9:6: warning: multi-character character constant [-Wmultichar]
 *ptr='495';
      ^
v.c:9:6: warning: overflow in implicit constant conversion [-Woverflow]

And the output of this program is-
239 �

53 5

Here I don't understand that why is it saying data overflow.
My analysis of the program-
As pointer is of character type and as size of char is 1 byte, so pointer will only point to the base address of var1. And hence value stored in the first byte of var1 will be the output. As the other 3 bytes won't be accessed by the pointer.
So I think in 1st printf 239 is printed as it is stored in the first byte of var1 and � is printed because %c means a character whose ASCII value is 495 which isn't possible.
And in 2nd printf 495 is a character constant. But by 53 and 5 is printed.
I don't understand. Please help. Thank you!

A: You are trying to point to an integer variable using a character pointer.
Pointer declaration needs to know which data type it is intended to point to. As it will be needed while dereferencing it. (How much bytes of data to be read from the memory?)
Here you are telling the compiler that the pointer points to 1 byte (char) and actually trying to point to integer (4 or 2 bytes); hence the errors. Also, '495', is multi character string.

redpajama_set_name: RedPajamaStackExchange


text:
\section*{Features of CV-MDI-QKD}

First of all, contrary to the claims of Xu et al.~\cite{Fehiu}, the CV
experiment of~\cite{CVMDIQKD} is performed with cheap room-temperature
components (optical modulators and homodyne detectors) in a regime of
parameters which are easily achievable in practice. Modulations of
$\varphi\simeq60$ shot noise units are relatively low with respect to what is
achievable ($100$ and more). Reconciliation efficiencies of $\xi\simeq97\%$
are currently state-of-the-art in CV-QKD
experiments~\cite{Jouguet,Elkouss,RMP}. An experimental excess noise
$\varepsilon\simeq0.01$ is not low but typical, fully comparable with the
values reported in the fibre-optic experiment of~\cite{Grangier2}, where the
experimental excess noise was estimated to be $\varepsilon\simeq0.001$ at
$10^{8\text{ }}$data points and $\varepsilon\simeq0.008$ at $10^{6\text{ }
$data points, for Bob's detection at $53$~km. At lower distances $\lesssim
25$~km (as is in our case), the excess noise is expected to be smaller, which
means that our experimental value $\varepsilon\simeq0.01$ can even be
considered relatively high. The robustness of CV-MDI-QKD against excess noise
can also be appreciated from the analysis done in the Supplementary Section
IE6 of~\cite{CVMDIQKD} (in particular, see Fig.~5 there), where the security
thresholds are proven to be robust against much higher excess noise
($\varepsilon=$ $0.1$).

Then, Xu et al.\cite{Fehiu} completely missed an important advantage of
CV-MDI-QKD, which is the extremely good performance of CV\ detection performed
at the relay. This crucial feature relies on two basic facts:

\begin{description}
\item[(1)] The detection setup of CV-MDI-QKD is completely different from that
of one-way CV-QKD\ protocols.

\item[(2)] CV Bell detection is deterministic and highly efficient (also in
telecom setups).
\end{description}

\noindent Let us explain these points in detail and the reader may also refer
to the panels in Fig.~\ref{PMscheme}.

In one-way (or point-to-point) CV-QKD protocols (see
Fig.~\ref{PMscheme}a), Alice prepares outgoing quantum states
while Bob detects states incoming from the channel. Because of
this configuration, only the loss within Alice's station can be
trusted and, therefore, neglected by re-scaling the signal level
at the output of Alice's box. The loss within Bob's station cannot
be re-scaled since it is added on top of channel loss and noise
(any re-scaling will also amplify the loss and noise of the
channel, without any signal-to-noise advantage). For this reason,
Bob's overall quantum efficiency is limited and this clearly
affects fibre-optic implementations at telecom wavelengths. For
instance, a quantum efficiency of $60\%$ was reported in
Ref.~\cite{Grangier2} due to optical manipulations and
photo-detection (however, note that this specific value of $60\%$
can be improved and, therefore, should not be considered as a
fundamental limit for the detection in one-way CV-QKD
protocols).\begin{figure*}[ptbh] \vspace{-3cm}
\par
\begin{center}
\includegraphics[width=0.99\textwidth] {loss3.eps}
\end{center}
\par
\vspace{-3.4cm}\caption{Experimental loss in CV-QKD configurations
(see text for more details). \textbf{a}, One-way CV-QKD protocol
with limited efficiency within Bob's station, due to unscalable
loss. \textbf{b}, Proof-of-principle demonstration of
CV-MDI-QKD~\cite{CVMDIQKD} in free-space at optical/infrared
regime ($1064$~nm) with $\simeq98\%$ efficiency for the CV Bell
detection. \textbf{c}, Proposal for a fibre-optic telecom
implementation of CV-MDI-QKD, where fibre-outcoupling and
free-space CV Bell detection achieve
$\simeq95\%$ efficiency.
\label{PMscheme
\end{figure*}

By contrast, in the setup of CV-MDI-QKD depicted in Fig.~\ref{PMscheme}b,
\textit{both} Alice and Bob prepare outgoing quantum states in their private
stations, where loss and noise are trusted. For this reason, both the signal
levels of Alice and Bob can be set at the output of their stations, so that
the effect of the internal losses can be completely neglected. Untrusted loss
and noise will only affect the channels and the detection at the relay. The
latter has extremely high efficiencies, indeed $\eta_{d}\simeq98\%$ in our
free-space experiment at optical wavelengths ($1064$ nm).

Here it is worth remarking that the CV version of\ Bell detection can be done
deterministically with simple linear optics and
photodetection~\cite{telereview}, contrarily to the $25\%$ probability success
affecting DV-MDI-QKD and the\ typical $50\%$ value bounding teleportation
experiments with photonic qubits~\cite{telereview,Bell1,Bell2,Bell3}. Most
importantly, the quantum efficiency of the homodyne detectors in CV Bell
detections is extremely high. Contrary to the incorrect claims of Xu et
al.~\cite{Fehiu}, homodyne detectors with high efficiencies have been seen in
both optical and telecom setups:

\begin{description}
\item[{[Optical Setups]}] These include the various free-space CV
teleportation experiments~\cite{telereview}, but also fibre-based experiments,
such as Ref.~\cite{Yone,Yoko}, where coupling efficiency to a fibre can be as
high as $98-99\%$ and the quantum efficiency of photo-detectors can be
$>99\%$, with an overall efficiency of about $97-98\%$~\cite{Akira}.

\item[{[Telecom Setups]}] For instance, see Ref.~\cite{Tobias2}, where the
performance of a balanced homodyne detection at $1550~$nm is $98\%$, by means
of InGaAs PIN diodes with an active area of $500~\mu$m in diameter and a
quantum efficiency of $\sim99\%$, together with a fringe visibility of
$99.5\%$ at the beamsplitter. See also Ref.~\cite{Tobias1}, where the overall
efficiency of the balanced homodyne detector at $1550~$nm is $95\%$. This is
performed in free space at the output of a $10$~m fibre, and the total $95\%$
efficiency includes both fibre in-coupling (the largest source of loss) and
outcoupling (estimated to be $0.1\%$)~\cite{Tobiasnote}.
\end{description}

A simple fibre-optic implementation of CV-MDI-QKD at telecom
wavelengths can be done as shown in Fig.~\ref{PMscheme}c. Here the
loss within Alice's and Bob's stations (e.g., associated with
fibre connections and modulators) can all be re-scaled as trusted
loss. At the relay, the CV Bell detection can be done in free
space. The efficiency associated with fibre out-coupling is close
to $100\%$ if the fibre facet is anti-reflection coated. The
efficient of the subsequent CV Bell detection is basically
determined by the homodyne detectors which may have $98\%$
efficiency at $1550~$nm~\cite{Tobias2}. For instance, the CV Bell
detection can be done in the simplified setup of
Ref.~\cite{CVMDIQKD} involving a balanced beam-splitter and two
photodectors. Considering $0.2$ dB insertion loss for the beam
splitter and $99\%$ efficiency for the diodes~\cite{Tobias2}, one
realizes a CV Bell detection with $\simeq95\%$ efficiency. This
means that the performance of our proof-of-principle experiment
can be achieved in a future fibre-optic telecom
implementation, contrary to the conjectures made by Xu et al.~\cite{Fehiu
\thinspace\ where the protocol was analysed by assuming too low efficiencies
for the detection at the relay (down to $85\%$).

Unfortunately, yet other claims made by Xu et al.~\cite{Fehiu} were wrong.
Contrarily to what they state:

\smallskip

\noindent\textbf{(i)~The asymptotic rate of~\cite{CVMDIQKD} is not an upper
bound but a lower bound with respect to all possible attacks}. In fact, the
experimental rate is computed from Alice and Bob's shared classical data
assuming the whole environment belongs to Eve. Then, the theoretical rate is
derived against optimal attacks. More precisely, this is minimized over all
two-mode Gaussian attacks in normal form after the application of the de
Finetti theorem and the extremality of Gaussian states~\cite{RMP}. This is in
contrast with the partial (and purely numerical) analyses in~\cite{Li,MaXC}
which only considered the simple case of two independent entangling cloner
attacks, as thoroughly discussed in Ref.~\cite{Carlo}. More details may be
found in~\cite{Notaprova}.

\smallskip

\noindent\textbf{(ii)~Finite-size effects against coherent
attacks~\cite{Jouguet,Elkouss,RMP} and composable security in the presence of
collective attacks~\cite{Leverrier} support our results}. It is true that our
theoretical rate is derived in the asymptotic limit of infinite signals but
there is no evidence that it would be sensibly affected by finite-size
analyses. In fact, the current finite-size analyses tend to the asymptotic
limit for blocks of $\gtrsim10^{8}$ data points (e.g., see Fig.~1\ of
\cite{Leverrier}), which is the size considered in
our\ experiment~\cite{CVMDIQKD}. This is also the size of data blocks
considered in the experiment of Ref.~\cite{Grangier2}, where the finite-size
key rate is shown to well-approximate the asymptotic regime, especially below
$30$~km, as is clear from Fig.~2 of \cite{Grangier2}. Note that
(point-to-point) coherent-state protocols are composable-secure against
general coherent attacks, but the present proof techniques are not sufficient
to prove fast convergence~\cite{Leverrier2,RevDIA}. The fact that a proof is
currently missing does not mean that such convergence cannot be shown with
another method, i.e., there is no fundamental reason to conjecture that the
composable-secure key rates of\ coherent-based CV-QKD\ protocols should not
fastly converge to the asymptotic values. Indeed this fast convergence has
been already proven in the most general case for squeezed-state
CV-QKD~\cite{RevDIA}. By contrast, we note that finite-size analysis seems to
be very demanding\ for DV-MDI-QKD, where blocks of $\gtrsim10^{10}$ data
points are needed for achieving reasonably non-zero rates with practical
detectors (see Fig.~4 of~\cite{CurtyFIN}).

\smallskip

\noindent\textbf{(iii)~The relay doesn't need to be in Alice's lab}. In fact,
all configurations (symmetric or asymmetric) show a non-trivial advantage with
respect to DV-MDI-QKD at metropolitan distances ($5-25$km).

\smallskip

\noindent\textbf{(iv)~The use of a single local oscillator is not a major
security flaw in CV-QKD and its removal is no longer an experimental
challenge}. The use of a single local oscillator is typical in all CV-QKD
implementations so far. Practical security against its potential manipulation
can be achieved if one implements an accurate real-time measurement of the
experimental shot noise~\cite{Loscill,RevDIA}. Furthermore, CV-QKD can also be
implemented using two independent local oscillators followed by classical
post-processing~\cite{Qi2,Soh,NoteREMAP}. Thus, the \textquotedblleft source
requirements\textquotedblright\ brought up by Xu et al.\ (Appendix~D
of~\cite{Fehiu}) are easily overcome. Regarding this issue of using a single
laser, it is important to remark that Xu et al.'s comment~\cite{Fehiu} is not
just against CV-MDI-QKD but the entire field of CV-QKD. According to Xu et
al.'s `criteria', all CV-QKD protocols implemented so far, including the first
ground-breaking table-top experiment of Ref.~\cite{Grangier} and the
long-distance experiment of Ref.~\cite{Grangier2} wouldn't be, as they put it,
\textquotedblleft properly designed QKD\ demonstrations\textquotedblright\ for
their use of a single local oscillator.

\smallskip

\noindent\textbf{(v)~Fast homodyne detectors exist plus CVs remain
superior even on slower clocks}. In the optical range, homodyne
detection can be done at GHz-bandwidths~\cite{HomGHZ}, with
$80$MHz detectors being available with efficiencies
$\gtrsim86\%$~\cite{BHD80} and, more recently, $100$MHz detectors
at $99\%$ efficiency~\cite{AkiraLAST}. This is a technology which
has large room of development at telecom wavelengths, where a
field implementation of CV-QKD has been already achieved at $1$MHz
clock~\cite{Grangier2}. This scenario has to be compared with the
$75$MHz clock rate implemented in DV-MDI-QKD~\cite{Tang}, while
$1$GHz has only been used for point-to-point BB84, with detector
efficiencies of about $20\%$~\cite{Luca} (now increasable up to
$55\%$~\cite{Shields1}). Here it is important to note that the
difference, in terms of bits per use, can be so large that CVs may
achieve higher rates than DVs while using much slower clocks. For
instance, in the case of point-to-point QKD, a $50$MHz-clock CV
protocol is already sufficient to outperform a $1$GHz-clock
protocol with DVs at metropolitan distances~\cite{Elkouss}. Since
there are about three orders-of-magnitude in the rate (bits per
use) between practical CV-MDI-QKD and practical DV-MDI-QKD, the CV
protocol could run on clocks which are three orders-of-magnitude
slower and still achieve the same performances of DVs. For this
reason, a fibre-based telecom implementation of CV-MDI-QKD at
$1~$MHz is hard to beat by any practical implementation of
DV-MDI-QKD (see below for a full clarification of the word
\textquotedblleft practical\textquotedblright\ in this
context).\begin{figure*}[ptbh] \vspace{-0.2cm}
\par
\begin{center}
\includegraphics[width=0.99\textwidth] {figureREPLY5.eps}
\end{center}
\par
\vspace{-0.9cm}\caption{Comparison between the rates (bits per
relay use) of CV-MDI-QKD and DV-MDI-QKD versus total Alice-Bob
distance (in fibre-equivalent at 0.2dB/km) and assuming different
configurations for the relay in the various panels
\textbf{a}-\textbf{d}. \textbf{a}, relay in Alice's lab. From
bottom to top we consider: (1) Rate of practical DV-MDI-QKD\ with
standard semiconductor detectors ($\eta_{d}\simeq14.5\%$,
$e_{d}\simeq1.5\%$, $Y_{0}\simeq6\times10^{-6}$, $f_{e}=1.16$).
(2) Rate of the optimal realistic DV-MDI-QKD\ with the best
semiconductor detectors ($\eta_{d}\simeq55\%$,
$Y_{0}\simeq5\times10^{-4}$). Lower bound of the gray band refers
to typical error $e_{d}\simeq1.5\%$, while the upper bound refers
to $e_{d}\simeq0.1\%$ ($f_{e}=1.16$ in all cases) (3) Rate of
ideal DV-MDI-QKD with cryogenic
93\%-efficiency SNSPDs ($\eta_{d}\simeq93\%$, $e_{d}\simeq0.1\%$, $Y_{0
\simeq10^{-6}$, $f_{e}=1.16$). (4) Rate of practical CV-MDI-QKD
with room-temperature cheap components ($\eta_{d}\simeq98\%$,
$\varepsilon \simeq0.01$, $\varphi\simeq60$, $\xi=97\%$); squares
are experimental data. (5) Rate of CV-MDI-QKD with ideal
reconciliation efficiency (as before but $\xi=100\%$). (6)
Secret-key capacity of the total channel between Alice and Bob,
lowerbounded by~\cite{Pirandola2009,reverse} and upperbounded
by~\cite{TGW}. \textbf{b}, as in \textbf{a}\ but with a 100m-fibre
between Alice and the relay. \textbf{c}, as in \textbf{a}\ but
with 1km-fibre between Alice and the relay. \textbf{d}, symmetric
case where Alice and Bob are equidistant (in simulated fibre) from
the relay; no experimental data for this specific configuration.}
\label{figure}
\end{figure*}

\bigskip

\section*{Actual comparison between CVs and DVs}

Having refuted the various incorrect claims and conjectures made by Xu et al.
regarding CVs, we now perfom a detailed comparison between CVs and DVs,
considering a realistic analysis of DV-MDI-QKD. We can easily see that
practical parameters and cheap components for DVs are certainly \textbf{not}
those stated in Xu et al.'s comment~\cite{Fehiu} but those considered by four
of these same authors in an earlier paper on \textquotedblleft practical
aspects\textquotedblright\ of DV-MDI-QKD~\cite{Xu}. Practical DV-MDI-QKD
involves standard single-photon detectors with $\eta_{d}\simeq14.5\%$
efficiency and a $Y_{0}\simeq6\times10^{-6}$ dark count rate, together with
typical values of the intrinsic error rate $e_{d}\simeq1.5\%$ and error
correction efficiency parameter $f_{e}=1.16$~\cite{Brassard}. This is
state-of-the-art for room-temperature (20
{{}^\circ
$C) or thermoelectrically cooled (-50
{{}^\circ
$C) semiconductor (InGaAs) avalanche photodiodes (APD)
detectors~\cite{Shields2,Zbinden}, typically operating at $10-30\%$ efficiency
but with increasing dark counts (see Fig.~2 of~\cite{Shields2}).

Assuming these realistic and practical parameters, one can easily compute an
estimate of the rate for DVs by assuming infinite decoy states, neglecting
finite-size effects and other errors such as time-jitter and mode mismatch
(see Appendix for details). From Fig.~\ref{figure} we see how the rate of the
practical DV-MDI-QKD is below that of the practical CV-MDI-QKD by $3-4$
orders-of-magnitude over metropolitan distances, from $6$km in the symmetric
case up to $25$km in the most asymmetric configuration.

It is interesting to study the maximum rate that one can achieve
with DVs by using semiconductor detectors. Since we are interested
in short to medium distances and high rates, the choice is for
detectors with the highest efficiency (despite their high dark
counts). The best solution appears to be the very recent
InGaAs/InP APDs operated in optimized self-differencing mode at
room temperature by Toshiba~\cite{Shields1}. These achieve
$\eta_{d}\simeq55\%$ efficiency with background rates $Y_{0}\simeq
5\times10^{-4}$ at 20
{{}^\circ
$C. Fixing $f_{e}=1.16$ and considering $e_{d}$ in the range $0.1\%-1.5\%$ we
can estimate the optimal performance of realistic DV-MDI-QKD in the lower gray
band shown in Fig.~\ref{figure}. As we see from the figure, the optimal
DV-MDI-QKD with semiconductor detectors is very good but still between 2 and 3
orders of magnitude below the already experimentally achieved CV rate over
typical metropolitan ranges.

In their comment, Xu et al.~\cite{Fehiu} compared our practical CV
experiment with a purely-theoretical numerical extrapolation for
DVs, which is based on nearly-ideal parameters and devices. In
particular, they consider an extremely-low intrinsic error rate
$e_{d}\simeq0.1\%$~\cite{Tang} (which would be very demanding to
realise with real-time modulators in a scalable practical
network)\ and the most advanced superconducting nanowire
single-photon detectors (SNSPDs). These detectors operate below 2K
with $\eta_{d}\simeq93\%$ efficiency and a
$Y_{0}\simeq6\times10^{-6}$ background rate~\cite{Marsili}. It is
interesting to note that two of the authors of Xu et
al.~\cite{Fehiu} seem to be aware of the limitations of the
applicability of these SNSPDs to a
real practical scenario, as they openly admitted in a previous publication
\begin{align*}
&  \text{\textquotedblleft The main drawback of these novel SNSPDs, }\\
&  \text{however, is their operating temperature, }\\
&  \text{which is currently of the order of }0.1\text{~K.\textquotedblright}\\
&  \text{[Lo, Curty \& Tamaki, \textit{Nature Photon. }\textbf{8},
595-604
(2014)]
\end{align*}
It is evident that such an ideal and cryogenic version of DV-MDI-QKD is too
demanding for the realistic construction of a scalable network (more details
may be found in~\cite{Notareti}). Remarkably, even considering these
over-optimistic parameters, our practical CV protocol is still $\simeq1$
order-of-magnitude better than this ideal extrapolation with DVs in all the
configurations of Fig.~\ref{figure}.

Furthermore, one can easily verify that the DV rate collapses down by another
$1-2$ orders-of-magnitude by employing more standard SNSPDs with $\eta
_{d}\lesssim45\%$~\cite{Tang}. By contrast, slight improvements in the
reconciliation efficiency of classical protocols of error correction and
privacy amplifications may provide further non-trivial gains for CVs. As we
see in Fig.~\ref{figure}, the CV theoretical rates with ideal reconciliation
($\xi=100\%$) is very close to the secret-key capacity of the total Alice-Bob
channel~\cite{CVMDIQKD}, achievable by CV-QKD protocols.

That being said, our analysis here does not want to discourage the
implementation of DV-MDI-QKD at metropolitan distances. While Xu et al.'s
cryogenic version of DV-MDI-QKD does not seem to be suitable for building a
realistic and low-cost metropolitan network, an implementation of DV-MDI-QKD
with room-temperature (or slightly-cooled) semiconductor-based single-photon
detectors is not only realistic but appealing, and may be the basis of a
secure quantum network with intermediate rates. We therefore strongly
encourage serious and careful research in this direction. It would also be
interesting to explore potential hybrid DV-CV approaches, as it is now
happening for other quantum protocols (e.g., see quantum
teleportation~\cite{telereview}).

In conclusion, our take-home message is the following: DV-MDI-QKD is very good
for long distances~\cite{Tang,EXP1,EXP2}, but its rate struggles to be
increased at various distances, thus motivating the proposal of alternate
strategies by the community~\cite{ignore}. By contrast,
CV-MDI-QKD~\cite{CVMDIQKD,Carlo} struggles with long distances but can
potentially provide much higher rates at the metropolitan range ($5-25$km),
extending what happens for point-to-point CV-QKD~\cite{Elkouss,ScaraniRMP}.
This statement must not come as a surprise since CV systems are fragile to
loss (limiting distance) but they can encode a lot of information thanks to
their theoretically infinite-dimensional Hilbert space~\cite{RMP}.
Furthermore, besides the use of cheap and practical devices, CVs can easily go broadband.

\bigskip

\textbf{Acknowledgments.} Authors thank feedback from J. H. Shapiro, A.
Furusawa, Z. Zhang, H. Zbinden, F. Grosshans, A. Leverrier, and E. Diamanti.
S.P. also would like to thank R. Filip, V. Usenko, N. L\"{u}tkenhaus, Q.
Zhang, and V. Scarani for comments/discussions on CV-MDI-QKD and CV-QKD. This
work has been supported by the EPSRC `UK Quantum Communications HUB'
(EP/M013472/1) and `qDATA' (EP/L011298/1), the Leverhulme Trust, the H. C.
{\O }rsted postdoc programme, and the Danish Agency for Science, Technology
and Innovation (Sapere Aude project).

\bigskip

redpajama_set_name: RedPajamaArXiv


text:
Jean-Pierre Le Goff peut désigner :
 Jean-Pierre Le Goff (1716-1790), orfèvre français du  ;
 Jean-Pierre Le Goff (1942-2012), écrivain, poète et plasticien français ;
 Jean-Pierre Le Goff (1948-), professeur de mathématiques, historien des sciences, des techniques et des arts français ;
 Jean-Pierre Le Goff (1949-), sociologue et philosophe français.

redpajama_set_name: RedPajamaWikipedia


text:
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The post Influencer Marketing Trends to Know in 2019 appeared first on B Squared Media.