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arXiv:1803.05171 · Applied Physics Letters

High fidelity field stop collection for polarization-entangled photon pair sources

Alexander Lohrmann, Aitor Villar, Arian Stolk, Alexander Ling

Published Oct 22, 2018• 17 citations
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Abstract

We present an experimental demonstration of a bright and high fidelity polarization entangled photon pair source. The source is constructed using two critically phase matched β-Barium Borate crystals with parallel optical axes, and photon pairs are collected after filtering with a circular field stop. Near-unity fidelities are obtained with detected pair rates exceeding 100 000 pairs/s mW, approaching the brightness of practical quasi-phase matched entangled photon sources. We find that the brightness scales linearly with the crystal length. We present models supporting the experimental data and propose strategies for further improvement. The source design is a promising candidate for emerging quantum applications outside of laboratory environments.

DOI
10.1063/1.5046962

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We present an experimental demonstration of a bright and high fidelity polarization entangled photon pair source. The source is constructed using two critically phase matched β-Barium Borate crystals with parallel optical axes, and photon pairs are collected after filtering with a circular field stop. Near-unity fidelities are obtained with detected pair rates exceeding 100 000 pairs/s mW, approaching the brightness of practical quasi-phase matched entangled photon sources. We find that the brightness scales linearly with the crystal length. We present models supporting the experimental data and propose strategies for further improvement. The source design is a promising candidate for emerging quantum applications outside of laboratory environments.
We present an experimental demonstration of a bright and high fidelity entangled photon source. The source is constructed using two critically phase matched β\betaβ-Barium Borate crystals with parallel optical axes and photon pairs are collected after filtering with a circular field-stop. Near unity fidelities are obtained with detected pair rates exceeding 100000 pairs/s/mW. Calculations of the angle dependent phase difference support the experimental data, and suggest strategies for further improvement. The source design is a promising candidate for emerging quantum applications outside of laboratory environments.
We present a polarization-entangled photon pair source operating in the visible light range around 532 nm. Employing a collinear crossed-crystal scheme with type-I degenerate phase matching in barium borate (BBO), our source achieves a brightness of 9.5 k pairs/s/mW and a quantum state fidelity of 98.3%, making it a candidate for integration in microscopes and make use of the advantages of mid-visible optimized single-photon detection technologies. In order to study potential applications, we present a trade-off between source brightness and polarization entanglement visibility and propose use cases for different filtering configurations of the source, capable of a brightness up to 1.23 M pairs/s/mW.
We present recent findings towards developing brighter entangled photon sources in critically phase matched (CPM) nonlinear crystals. Specifically, we use type-I collinear phase matching at non-degenerate wavelengths in parallel β-Barium Borate (BBO) crystals to generate pairs of polarization entangled photons for free-space quantum key distribution (QKD). We first review the entangled source configuration and then discuss ways to further improve the source brightness by means of tailoring the pump and collection modes. We present preliminary results that may lead to brighter entangled photon sources that are intrinsically robust to changes in their environment.
We present an optical design where polarization-entangled photon pairs are generated within two β\betaβ-Barium Borate crystals whose optical axes are parallel. This design increases the spatial mode overlap of the emitted photon pairs enhancing single mode collection without the need for additional spatial walk-off compensators. The observed photon pair rate is at least 65000 pairs/s/mW with a quantum state fidelity of 99.37±0.13%99.37\pm0.13\%99.37±0.13% when pumped with an elliptical spatial profile.
We report on an ultrabright beamlike source of polarization-entangled photon pairs that is suitable for the task of multiphoton quantum information processing. The photon pairs are generated from a beamlike type-II parametric downconversion process in two adjacently located but 180 degrees rotated beta-barium borate crystals. Approximately 30,000 s(-1) entangled photon pairs are recorded experimentally with only 100 mW pump power. The fidelity of the generated entangled state as compared with a Bell state is measured to be 0.974 with the method of quantum state tomography. With this source, we also obtain a violation of Bell's inequality by 61 standard deviations in just a few seconds.