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Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)

Quantum frequency conversion of visible single photons from a quantum dot to a telecom band

Andreas Lenhard, Sebastian Zaske, Christian Kessler, Jan Kettler, Carsten Arend, Christian Hepp, Roland Albrecht, W.-M. Schulz, Michael Jetter, Peter Michler, Christoph Becher

Published May 1, 2013• 0 citations
Publisher

Abstract

Establishing a network of quantum systems will be based on single photons as flying qubits. For a long range transmission, wavelengths in the low-loss telecom bands will be necessary. As such a network may consist of dissimilar systems emitting at different wavelengths, an interface will be required converting the photons to the telecom band without disturbing the single photon quantum properties. We here demonstrate frequency down-conversion of single photons from a quantum dot and prove the preservation of the single photon character [1].

DOI
10.1109/cleoe-iqec.2013.6801620

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Establishing a network of quantum systems will be based on single photons as flying qubits. For a long range transmission, wavelengths in the low-loss telecom bands will be necessary. As such a network may consist of dissimilar systems emitting at different wavelengths, an interface will be required converting the photons to the telecom band without disturbing the single photon quantum properties. We here demonstrate frequency down-conversion of single photons from a quantum dot and prove the preservation of the single photon character [1].
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On-demand indistinguishable single-photon sources are essential for quantum networking and communication. Semiconductor quantum dots are among the most promising candidates, but their typical emission wavelength renders them unsuitable for use in fiber networks. Here, we present quantum frequency conversion of near-infrared photons from a bright quantum dot to the telecommunication C-band, allowing integration with existing fiber architectures. We use a custom-built, tunable 2400 nm seed laser to convert single photons from 942 nm to 1550 nm in a difference-frequency generation process. We achieve an end-to-end conversion efficiency of ≃35%, demonstrate count rates approaching 1 MHz at 1550 nm with g(2)(0)=0.043(1), and achieve Hong-Ou-Mandel (HOM) visibilities of 60%. We expect this scheme to be preferable to quantum dot sources directly emitting at telecom wavelengths for fiber-based quantum networking.
Quantum network consisting of separate nodes processing information and linked by quantum channels is a promising and widely investigated general architecture for scalable and distributed quantum computing [1]. The most feasible proposals for realisation of such a network involve matter-based nodes (e.g. trapped atoms or ions or solid-state systems) communicating by photons [2]. This approach combines advantages of long-living and precisely manipulated systems for nodes with fast and convenient for long distance information transfer ones. Implementation of such a scheme opens up a lot of research challenges where establishing a reliable channel for quantum state transfer between two nodes by photons is essential, once the nodes are operating. It would by particularly convenient to have a standard channel that can different systems be talking to and the telecom band photons are good candidates for that because of well-established optical fiber infrastructure. In our work we implement a single photon frequency conversion to telecom band so that quantum systems with different emitting frequencies could be used in such a network. This approach also permits to minimize the losses and increase distances to 10s-kilometre range by exploiting the lowest attenuation band in fibers. The work is aimed in particular on developing device capable of converting photons produced by P3/2-D5/2transition in40Ca+ ion that corresponds to 854.2 nm wavelength as a promising candidate for the network nod.
In a typical quantum repeater scenario, remote quantum memories have to be interconnected by flying qubits transmitted in quantum channels. e.g. single photons in photonic fiber links. To establish long-distance communication, photons in the low-loss telecom wavlength regime are desirable. However, the majority of the candidates for quantum memories such as trapped atoms or ions, rare earth ensembles, color centers in diamond, atomic ensembles etc. possess optical transitions merely in the visible or near-infrared spectral regime below 1000 nm. One possible solution is the transduction of these wavelengths to the telecom region via quantum frequency conversion (QFC) based on three-wave-mixing processes in a nonlinear χ(2)-medium. Technical achievements in recent years enabled high conversion efficiencies and low conversion-induced noise contributions resulting in signal-to-background ratios high enough to demonstrate the preservation of several classical and quantum properties of the photons, e.g. first- and second-order coherence [1], time-bin entanglement [2], polarization entanglement [3] or indistinguishability [4]. QFC thus provides a powerful toolbox to interface quantum systems to the telecom bands and beyond that yet to interconnect dissimilar quantum systems.
Abstract On‐demand single‐photon sources emitting pure and indistinguishable photons at the telecommunication wavelength are critical assets toward the deployment of fiber‐based quantum networks. Indeed, single photons may serve as flying qubits, allowing communication of quantum information over long distances. Self‐assembled InAs quantum dots embedded in GaAs constitute an excellent nearly deterministic source of high‐quality single photons, but the vast majority of sources operate in the 900–950 nm wavelength range, precluding their adoption in a quantum network. A quantum frequency conversion scheme is presented here for converting single photons from quantum dots to the telecommunication C band, around 1550 nm, achieving 40.8% end‐to‐end efficiency, while maintaining both high purity and a high degree of indistinguishability during conversion with measured values of and , respectively.
We demonstrate efficient (>30%) quantum frequency conversion of visible single photons (711 nm) emitted by a quantum dot to a telecom wavelength (1313 nm). Analysis of the first- and second-order coherence before and after wavelength conversion clearly proves that pivotal properties, such as the coherence time and photon antibunching, are fully conserved during the frequency translation process. Our findings underline the great potential of single photon sources on demand in combination with quantum frequency conversion as a promising technique that may pave the way for a number of new applications in quantum technology.