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Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE

Multipli-entangled photon spontaneous parametric down-conversion source

Michael L. Fanto, Reinhard K. Erdmann, Paul M. Alsing, Corey J. Peters, Enrique J. Galvez

Published May 13, 2011• 0 citations
Publisher

Abstract

In this work, we discuss a novel compact source that generates six pairs of entangled photons via spontaneous parametric down-conversion from a single pass of a pump beam through a crystal assembly. The experimental demonstrations reported are at 810 nm so as to utilize high quantum efficiency Si-APD detectors, but the design can be readily implemented in other wavelength regimes including the telecom bands near 1550 nm. An immediate application of this source enables particular multi-qubit cluster states to be generated in a highly compact unidirectional configuration. This can significantly simplify the interferometric stability, as well as feed-forward methods required in photon-based quantum logic circuitry.

DOI
10.1117/12.883261

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In this work, we discuss a novel compact source that generates six pairs of entangled photons via spontaneous parametric down-conversion from a single pass of a pump beam through a crystal assembly. The experimental demonstrations reported are at 810 nm so as to utilize high quantum efficiency Si-APD detectors, but the design can be readily implemented in other wavelength regimes including the telecom bands near 1550 nm. An immediate application of this source enables particular multi-qubit cluster states to be generated in a highly compact unidirectional configuration. This can significantly simplify the interferometric stability, as well as feed-forward methods required in photon-based quantum logic circuitry.
1. ABSTRACT In this work, we discuss a novel compact source that generates six pairs of entangled photons via spontaneous parametric down-conversion from a single pass of a pump beam through a crystal assembly. The experimental demonstrations reported are at 810 nm so as to utilize high quantum efficiency Si-APD detectors, but the design can be readily implemented in other wavelength regimes including the telecom bands near 1550 nm. An immediate application of this source enables particular multi-qubit cluster states to be generated in a highly compact unidirectional configuration. This can significantly simplify the interferometric stability, as well as feed-forward methods required in photon-based quantum logic circuitry.
This paper expands upon prior work on an entangled photon source generating six pairs of photons via spontaneous parametric down-conversion in a single pass configuration. Experimental results measuring entangled photons at 810 nm are shown and other wavelength regimes will be discussed. The design and fabrication considerations for a group velocity matched (GVM) superlattice photon source are discussed. An application of this source enables various multiqubit cluster states to be generated in a compact unidirectional configuration. This configuration simplifies the interferometric stability for any associated feed-forward methods required in photon-based quantum logic circuitry.
Using the process of spontaneous parametric down-conversion in a two-crystal geometry, we have generated a source of polarization-entangled photon pairs that is more than ten times brighter, per unit of pump power, than previous sources, with another factor of 30 to 75 expected to be readily achievable. We have measured a high level of entanglement between photons emitted over a relatively large collection angle, and over a 10-nm bandwidth. As a demonstration of the source capabilities, we obtained a 242-\ensuremath{\sigma} violation of Bell's inequalities in less than three minutes, and observed near-perfect photon correlations when the collection efficiency was reduced. In addition, both the degree of entanglement and the state purity should be readily tunable.
We present an experimental setup for generation of entangled-photon pairs via spontaneous parametric down-conversion, based on the femtosecond-pulsed laser. Our entangled-photon source utilizes a 76-MHz-repetition-rate, 100-fs-pulsewidth, mode-locked, ultrafast femtosecond laser, which can produce, on average, more photon pairs than a cw laser of an equal pump power. The output infrared pump photons (λ = 810 nm) are first up-converted to blue light (λ = 405 nm) and, subsequently, down-converted in a 1.5-mm-thick, type-II BBO crystal via spontaneous down-conversion. The resulting entangled pairs are counted by a pair of high-quantum-efficiency, single-photon, silicon avalanche photodiodes. The total down-conversion efficiency of our system, corresponding criterion of the pump power for real entangled coincident events, has been calculated to be 0.86 × 10-9. Our apparatus is intended as an efficient source/receiver system for the quantum communications and quantum cryptography applications.
Entangled photon sources (EPSs) are essential building blocks for scalable quantum communication and quantum key distribution (QKD). We present a stable, highly nondegenerate EPS based on type-0 spontaneous parametric down-conversion (SPDC) in a crossed-crystal configuration, generating photon pairs at 680~nm and 1550~nm when pumped by a 473~nm laser. This wavelength combination, reported here for the first time, simultaneously benefits from the peak detection efficiency of the most of the Si-SPADs in the visible/near-infrared spectral range and the low-loss fiber transmission of the telecom C-band. This configuration provides the most favorable balance between performance and cost for detection using Si-SPADs and InGaAs detectors. The source exhibits a measured spectral bandwidth of 300~GHz, corresponding to a spectral brightness of up to 1.9×1031.9\times 10^31.9×103~pairs~s−1^{-1}−1~mW−1^{-1}−1~GHz−1^{-1}−1. Heralding efficiencies reach 18~\% (signal) and 34~\% (idler) with Si-SPAD and superconducting nanowire single-photon detectors (SNSPD) detection. The entangled state achieves visibilities of (97.3±1.0) %(97.3\pm 1.0)\,\%(97.3±1.0)% in the H/V basis and (94.9±1.6) %(94.9\pm1.6)\,\%(94.9±1.6)% in the D/A basis, yielding a fidelity of ≥(96.1±1.3) %\geq(96.1\pm1.3)\,\%≥(96.1±1.3)%. These results establish the presented EPS as a practical wavelength-hybrid platform for fiber-based QKD and emerging long-haul quantum network architectures.