Entanglement in an ensemble of electron and nuclear spins in silicon
Entanglement is the basis of quantum computing. Although spin ensembles, such as those used in liquid-state nuclear magnetic resonance have been examined, the results contain no entanglement and ultimately constitute classical simulations of quantum algorithms.
One of the causes of the problem is short coherence time of a quantum bit in the host material. Researchers have engineered phosphorus-doped silicon to be composed solely of 28Si stable isotope.
High-field (3.4 T), low-temperature (2.9 K) electron spin resonance of P in Si was combined with hyperpolarization of the 31P nuclear spin to obtain an initial state of sufficient purity to create a non-classical, inseparable state. The state was verified using density matrix tomography based on geometric phase gates, and entanglement operation was performed simultaneously on high density spin pairs as large as 1010.
Researchers suggest that the present result satisfies one of the essential requirements for a silicon-based quantum information processor. A column of Nature News pointed out the importance of the result and cited several challenges suggested by specialists toward quantum information processor.
More information:
Stephanie Simmons, et al., "Entanglement in a solid-state spin ensemble", Nature, Published online 19 January 2011, DOI: doi:10.1038/nature09696
Provided by National Institute for Materials Science
