Quantum-Dot-Spin Single-Photon Interface

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In this paper SOLID researcher A. Imamoglu and colleagues at ETH-Zürich show how the spin-state-dependent resonance fluorescence from a charged quantum dot can be used to realize a classical single spin-photon interface. The measurement is background free and shows how detecting the scattered photon intensity with 300 ps time resolution projects the quantum dot spin into a definite spin eigenstate with a fidelity exceeding 99%. The bunching of resonantly scattered photons reveals information about electron spin dynamics. High-fidelity fast spin-state initialization heralded by a single photon enables the realization of quantum information processing tasks such as nondeterministic distant spin entanglement. Given that the group could suppress the measurement back action to well below the natural spin-flip rate, the work shows how a quantum non-demolition measurement of a single spin could be achieved by increasing the fluorescence collection efficiency by a factor of 10 or more using a photonic nanostructure.

S. T. Yılmaz, P. Fallahi, and A. Imamoğlu
Phys. Rev. Lett. 105, 033601 (2010)