A technique for making rewritable computer chips uses laser light to control the spin of an atom’s nucleus to encode information, bringing ultrafast quantum computing a step closer to reality. Current electronic devices, which are approaching the upper limits in processing speed, rely on etching a pattern into a semiconductor to create a chip or integrated circuit. These interconnection patterns serve as highways to shuttle information around circuits, but there is a drawback. Inside this apparatus, a probe sends radio-frequency pulses onto the coil used for pulsed spin manipulation of a semiconductor sample. The technique could be used to make computer chips rewritable. “Once the chip is printed, it can only be used one way,” said Dr. Jeffrey Reimer, a University of California, Berkeley (UCB), professor of chemical and biomolecular engineering. Now, scientists from UCB and The City College of New York (CCNY) have looked to the emerging sciences of spintronics and quantum computing to remedy these problems. They used laser light to pattern the alignment of spin within atoms so that the pattern can be rewritten on-the-fly. The technique could lead to rewritable spintronic circuits. Although conventional computing and digital electronics rely on translating electrical charges into the binary code of zeros and ones, spintronics computers use the quantum property of electron spin, which enables the electron to store any number between zero and one. This allows multiple computations to be completed simultaneously, and processing power to be significantly increased. Attempts to use electrons for quantum computing have been plagued, however, by their spins’ tendency to switch back and forth rapidly. This makes them very unstable vehicles for holding information. To suppress the random switching of electrons back and forth, the scientists used laser light to produce long-lasting nuclear spin “magnets” that pull, push or stabilize the spins of the electrons. This was achieved by illuminating a sample of gallium arsenide with a pattern of light, similar to how lithography etches a physical pattern onto traditional integrated circuits. The illuminated pattern aligned the spins of all the atomic nuclei, along with the electrons, all at once, creating a spintronic circuit. “What you could have is a chip you can erase and rewrite on-the-fly with just the use of a light beam,” said Carlos Meriles, a CCNY professor of physics. Changing the pattern of light altered the layout of the circuit instantly. “If you can actually rewrite with a beam of light and alter this pattern, you can make the circuit morph to adapt to different requirements,” he said. “Imagine what you can make a system like that do for you.” The results were published in Nature Communications (doi: 10.1038/ncomms1918).