Cavity-enhanced two-photon interference using remote quantum dot sources

Abstract

Quantum dots in cavities have been shown to be very bright sources of indistinguishable single photons. Yet the quantum interference between two such bright quantum dot sources, a critical step for photon-based quantum computation, still needs to be investigated. Here, we report on such a measurement, taking advantage of a deterministic fabrication of the devices. We show that cavity quantum electrodynamics can efficiently improve the quantum interference between remote quantum dot sources: Poorly indistinguishable photons can still interfere with good contrast with high quality photons emitted by a source in the strong Purcell regime. Our measurements and calculations show that cavity quantum electrodynamics is a powerful tool for interconnecting several quantum dot devices. Recent years have seen impressive progress in the implementation of quantum functionalities using semiconductor quantum dots (QDs). These artificial atoms [1] have been used to generate flying quantum bits in the form of single photons [2] or entangled photon pairs [3,4], to map and optically manipulate the quantum information encoded onto a single stationary electron [5,6] or hole spin [7], as well as to implement optical logic gates [8][9][10]. The potential of QD-based single photon sources lies in their deterministic and pure quantum statistics, as opposed to the parametric down-conversion sources currently used in quantum optics. At saturation, the QD emits a single photon with a probability close to one and a vanishing probability of emitting a second photon. However, collecting single photons emitted by a QD is challenging: The collection efficiency is limited to 1%-2% for a QD in bulk [11] and to 5%-10% for a QD in a planar cavity structure. New strategies have been developed to reach high collection efficiencies (in the 40%-90% range) such as inserting the QD in one-dimensional photonic crystal or nanowire waveguides [11][12][13][14], in photonic crystal nanocavities [15], microdisk cavities [16], or micropillar cavities [17].Since the first demonstration in 2002 [18], the coalescence of photons successively emitted by a single QD has been widely investigated. Various strategies have been developed to minimize the environment-induced dephasing (phonons, charge noise). One approach consists of using a strictly resonant excitation to create the carriers directly into the QD state and reduce the time jitter of the photon emission [9,[19][20][21][22][23]. Another approach consists of using the Purcell effect by inserting the QD in a microcavity. The acceleration of spontaneous emission reduces the effect of dephasing * Present address: Institut fur Halbleriteroptik und Funktionelle Grenzflachen, Universitat Stuttgart, Germany.† pascale.senellart@lpn.cnrs.fr [17,18,23] and leads to an efficient extraction of photons: Ultrabright sources of highly indistinguishable photons were recently reported using this approach [17]. The scalability of a quantum network based on QDs relies on the possibility of interconnecting two QD devices. Pioneer...

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