Nature 491, 426–430 (2012) Nature 491, 421–425 (2012)

A combination of the long-distance transport offered by flying qubits — quantum information stored in light — and the storage capabilities of stationary matter-based qubits is central to many of the designs for future quantum-information processors. Two teams of researchers have now demonstrated how this can be achieved in nanoscale semiconductor devices by entangling a single spin with a single photon.

Both Weibo Gao and Kristiaan De Greve and their respective co-workers investigated quantum dots that stored a single electron. To this they added an optically excited electron–hole pair, which emitted a photon as it relaxed. The researchers demonstrated a quantum correlation between the properties of this photon and the spin of the electron left behind.

Gao and colleagues demonstrated entanglement between spin and photon wavelength; De Greve et al., on the other hand, chose the polarization of the photon. This allowed them to shift the wavelength of the light from 900 nm to potentially more useful telecommunication wavelengths.