Abstract
Entangling a single spin to the polarization of a single incoming photon, generated by an external source, would open new paradigms in quantum optics such as delayed-photon entanglement, deterministic logic gates or fault-tolerant quantum computing. These perspectives rely on the possibility that a single spin induces a macroscopic rotation of a photon polarization. Such polarization rotations induced by single spins were recently observed, yet limited to a few 10−3 degrees due to poor spin–photon coupling. Here we report the enhancement by three orders of magnitude of the spin–photon interaction, using a cavity quantum electrodynamics device. A single hole spin in a semiconductor quantum dot is deterministically coupled to a micropillar cavity. The cavity-enhanced coupling between the incoming photons and the solid-state spin results in a polarization rotation by ±6° when the spin is optically initialized in the up or down state. These results open the way towards a spin-based quantum network.
Highlights
Entangling a single spin to the polarization of a single incoming photon, generated by an external source, would open new paradigms in quantum optics such as delayed-photon entanglement, deterministic logic gates or fault-tolerant quantum computing
Another venue to spin–photon interfacing is to make use of the rotation of optical polarization induced by a single spin placed at the centre of a cavity-quantum electrodynamics (QED) device
Faraday or Kerr polarization rotation in a magnetized medium is routinely used for magnetic material characterization[19], observations of Kerr rotation induced by a single spin were reported only recently[20,21,22], with rotation angles in the few 10 À 3 degree range
Summary
Entangling a single spin to the polarization of a single incoming photon, generated by an external source, would open new paradigms in quantum optics such as delayed-photon entanglement, deterministic logic gates or fault-tolerant quantum computing. Spin–photon entanglement has been demonstrated between a photon emitted by a quantum emitter and the spin degree of freedom of the same emitter[6,7,8] Another venue to spin–photon interfacing is to make use of the rotation of optical polarization (so-called Faraday or Kerr rotation) induced by a single spin placed at the centre of a cavity-quantum electrodynamics (QED) device. This approach allows interfacing a resident spin with a photon generated by an external source, opening new possibilities in quantum optics. We show how quantum measurements and quantum entanglement can be implemented with realistic cavity-QED devices
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