Sources: ETH Zürich [press release], PNAS [abstract]
quote: By your logic, there's no such thing as "digital circuit".
quote: The difference between "digital" and "analog" circuits is the way we interpret their input/output signals. If we only care about the specific ranges those signals fall into, rather than their precise values, then the signals are digital. If both input and output signals are digital, then the circuit is digital. If input is digital, and output is analog, or vice versa, then the circuit is mixed signal (for example, ADC or DAC). If both input and output signals are analog, then the circuit is analog.
quote: Presence of capacitors, or any particular physical implementation, has nothing to do with a circuit being digital or analog.
quote: You can build a digital circuit with wooden sticks, or an analog circuit with transistors.
quote: I've never called this circuit "digital".
quote: My point is that it does not make sense to call any circuit "digital", "analog", or "mixed signal" until you know what kind of signal flows through the circuit.
quote: That's why I disagreed with your original statement that this circuit can't be digital just because it has a capacitor.
quote: Your argument about a black box is not relevant, because I am looking inside the circuit.
quote: "If I am looking inside a DRAM cell, and the signal there appears digital, from my perspective, then the DRAM cell is a digital circuit to me."
quote: What's relevant here is, again, the nature of the signal, not the design of a circuit.
quote: Do you see my point?
quote: Just to be clear, what is your definition of a digital or analog circuit?
quote: it does not care about the circuit (it's not a circuit simulator anyway).