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Efficient heralding of pure single-photons at telecom wavelength from pulsed cavity-enhanced SPDC

Xavier Barcons Planas, Helen M. Chrzanowski, Leon Meßner, Janik Wolters

Published Jan 1, 2024• 0 citations
Publisher

Abstract

Highly efficient sources of pure single photons are essential for photonic quantum technologies. We present a source of pure single-photons with 85% heralding efficiency based on pulsed spontaneous parametric down-conversion in a monolithic cavity.
DOI
10.1364/cleo_fs.2024.ftu3o.6

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Photonic quantum technologies require efficient sources of pure single photons. We present a heralded single-photon source based on spontaneous parametric down-conversion in a monolithic cavity optimized for high spectral and spatial purity. The source heralds single photons at a wavelength of 1540 nm and a spectral bandwidth of 168 MHz, with a maximum heralding efficiency of 70% including all transmission and detection losses, while keeping the multi-photon contamination below 3%. The cavity enhancement predominantly generates photons into the central cavity mode, with a theoretical upper bound on the spectral purity of 79.4% arising from nonzero overlap with adjacent cavity modes. Spectral isolation of the central cavity mode with an etalon yields an increased measured spectral purity of (96.2 ±\pm± 2.7)%.
Photonic quantum technologies require efficient sources of pure single photons. We present a heralded single-photon source based on spontaneous parametric down-conversion in a monolithic cavity optimized for high spectral and spatial purity. The source heralds single photons at a wavelength of 1540 nm and a spectral bandwidth of 168 MHz, with a maximum heralding efficiency of 70% including all transmission and detection losses, while keeping the multi-photon contamination below 3%. The cavity enhancement predominantly generates photons into the central cavity mode, with a theoretical upper bound on the spectral purity of 79.4% arising from nonzero overlap with adjacent cavity modes. Spectral isolation of the central cavity mode with an etalon yields an increased measured spectral purity of (96.2±2.7)%.
Photonic quantum technologies rely on two-photon interference, which is fundamentally constrained by photon purity. Consequently, the efficient generation of highly pure single photons is essential for scalability. Heralded single photons from spontaneous parametric down-conversion (SPDC) photon-pair sources are a viable option; however, multimode emission reduces both their purity and heralding efficiency. Techniques such as waveguide geometries, group velocity matching, and cavity resonators improve single-mode behaviour. A monolithic cavity design [1] has been considered for further stability, tunability and robustness. In this work, we present a photon-pair source using pulsed SPDC in a monolithic non-linear crystal cavity, where cavity confinement ensures well-defined spatial and spectral modes.
The generation of high purity single photons and entangled photon pairs is a crucial first step in many quantum optics experiments, including those that require quantum teleportation [1], entanglement swapping [2], and the generation of multi-photon entanglement [3]. The most widely used and established approach for creating photon pairs is spontaneous parametric down conversion (SPDC) - where pump photons undergo a non-linear optical process to create a down-converted photon pair [4]. Traditionally, the generation of high-purity heralded single photons required severe spectral filtering, introducing additional loss. However, through careful engineering of spectral correlations of the down-converted photon pairs one can circumvent the need for filtering and avoid the accompanying reduction in heralding efficiency.