Entanglement in an Ensemble of Electron and Nuclear Spins in Silicon

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 10^10.

Researchers suggest that the present result satisfies one of the essential requirements for a silicon-based quantum information processor. A column of “Nature News” (see link below) pointed out the importance of the result and cited several challenges suggested by specialists toward quantum information processor.

Journal information

Stephanie Simmons, Richard M. Brown, Helge Riemann, Nikolai V. Abrosimov, Peter Becker, Hans-Joachim Pohl, Mike L. W. Thewalt, Kohei M. Itoh & John J. L. Morton , “Entanglement in a solid-state spin ensemble”, Nature, Published online 19 January 2011, DOI: doi:10.1038/nature09696