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arXiv · 1705.05272

Correlations and entanglement of microwave photons emitted in a cascade decay

Simone Gasparinetti·Marek Pechal·Jean-Claude Besse·Mintu Mondal·Christopher Eichler·Andreas Wallraff
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Abstract

An excited emitter decays by radiating a photon into a quantized mode of the electromagnetic field, a process known as spontaneous emission. If the emitter is driven to a higher excited state, it radiates multiple photons in a cascade decay. Atomic and biexciton cascades have been exploited as sources of polarization-entangled photon pairs. Because the photons are emitted sequentially, their intensities are strongly correlated in time, as measured in a double-beam coincidence experiment. Perhaps less intuitively, their phases can also be correlated, provided a single emitter is deterministically prepared into a superposition state, and the emitted radiation is detected in a phase-sensitive manner and with high efficiency. Here we have met these requirements by using a superconducting artificial atom, coherently driven to its second-excited state and decaying into a well-defined microwave mode. Our results highlight the coherent nature of cascade decay and demonstrate a novel protocol to generate entanglement between itinerant field modes.

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Simone Gasparinetti, Marek Pechal, Jean-Claude Besse, Mintu Mondal, Christopher Eichler, Andreas Wallraff. 2017-05-15. Correlations and entanglement of microwave photons emitted in a cascade decay. https://doi.org/10.1103/physrevlett.119.140504

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