This new experiment explores a fundamental limit for the storage and processing of information in silicon-based quantum computers. Here, the relevant qubits are the spin of electrons bound to isolated phosphor atoms. Applying a novel optical method to an ultrapure, isotopically enriched silicon crystal from the Avogadro project allows the unambiguous identification of the relevant spin relaxation processes and reveals spin relaxation times at low temperatures exceeding 20 hours.
Several groups worldwide envision quantum information processing based on the spin of isolated phosphor atoms in silicon and previous experiments have shown remarkable success concerning high-fidelity qubits and readout of individual spins. Currently, these experiments are limited technologically but in the long run the ultimate limit will be the intrinsic spin relaxation time. This spin relaxation time has been studied by electron spin resonance already half a century ago, but the results were so far inconclusive at low temperatures. The new experimental results provide this missing piece of the puzzle.
Further informations: Low Temperature Relaxation of Donor Bound Electron Spins in 28Si:P