Partially Nondestructive Continuous Detection of Individual Traveling Optical Photons

Abstract

We report the continuous and partially nondestructive measurement of optical photons. For a weak light pulse traveling through a slow-light optical medium (signal), the associated atomic-excitation component is detected by another light beam (probe) with the aid of an optical cavity. We observe strong correlations of g ð2Þ sp ¼ 4.4ð5Þ between the transmitted signal and probe photons. The observed (intrinsic) conditional nondestructive quantum efficiency ranges between 13% and 1% (65% and 5%) for a signal transmission range of 2% to 35%, at a typical time resolution of 2.5 μs. The maximal observed (intrinsic) device nondestructive quantum efficiency, defined as the product of the conditional nondestructive quantum efficiency and the signal transmission, is 0.5% (2.4%). The normalized cross-correlation function violates the Cauchy-Schwarz inequality, confirming the nonclassical character of the correlations. DOI: 10.1103/PhysRevLett.116.033602 Photons are unique carriers of quantum information that can be strongly interfaced with atoms for quantum state generation and processing [1][2][3][4][5][6][7][8][9]. Quantum state detection, a particular type of processing, is at the heart of quantum mechanics and has profound implications for quantum information technologies. Photons are standardly detected by converting a photon's energy into a measurable signal, thereby destroying the photon. Nondestructive photon detection, which is of interest for many quantum optical technologies [10][11][12], is possible through strong nonlinear interactions [12] that ideally form a quantum nondemolition measurement [13]. To date, quantum nondemolition measurement of single microwave photons bound to cooled cavities has been demonstrated with high fidelity using Rydberg atoms [14][15][16], and in a circuit cavity quantum electrodynamics system using a superconducting qubit [17].For quantum communication and many other photonics quantum information applications [18,19], it is desirable to detect traveling optical photons instead of photons bound to cavities. Previously, a single-photon transistor was realized using an atomic ensemble inside a high finesse cavity where one stored photon blocked the transmission of more than one cavity photon and could still be retrieved [5]. Such strong cross-modulation [20] can be used for all-optical destructive detection of the stored optical photon, but the parameters in that experiment did not allow nondestructive detection with any appreciable efficiency. High-efficiency pulsed nondestructive optical detection has recently been achieved using a single atom in a cavity [21]. In that implementation, the atomic state is prepared in 250 μs, altered by the interaction with an optical pulse reflected from the cavity, and read out in 25 μs.In this Letter, we realize partially nondestructive, continuous detection of traveling optical photons with microsecond time resolution. The signal photons to be detected propagate through an atomic ensemble as slow-light polaritons [22] under conditions of electro...

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Heralded Interaction Control between Quantum Systems

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“…When we operate on cavity and atomic resonance, t is given by t ¼ 1=ð1 þ ηÞ, where η ¼ 8.6 is the single-atom cooperativity [24].…”