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arXiv:0710.1143 · New Journal of Physics

High coherence photon pair source for quantum communication

Matthäus Halder, A. Beveratos, Rob Thew, Corentin Jorel, Hugo Zbinden, Nicolas Gisin

Published Feb 18, 2008• 76 citations
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Abstract

This paper reports a novel single mode source of narrow-band entangled photon pairs at telecom wavelengths under continuous wave (CW) excitation, based on parametric down conversion. For only 7 mW of pump power it has a created spectral radiance of 0.08 pairs per coherence length and a bandwidth of 10 pm (1.2 GHz). The effectively emitted spectral brightness reaches 3.9 × 10 5 pairs s −1 pm −1 . Furthermore, when combined with low jitter single photon detectors, such sources allow for the implementation of quantum communication protocols without any active synchronization or path length stabilization. A Hong–Ou–Mandel (HOM)-dip with photons from two autonomous CW sources has been realized demonstrating the setup's stability and performance.

DOI
10.1088/1367-2630/10/2/023027

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This paper reports a novel single mode source of narrow-band entangled photon pairs at telecom wavelengths under continuous wave (CW) excitation, based on parametric down conversion. For only 7 mW of pump power it has a created spectral radiance of 0.08 pairs per coherence length and a bandwidth of 10 pm (1.2 GHz). The effectively emitted spectral brightness reaches 3.9 × 10 5 pairs s −1 pm −1 . Furthermore, when combined with low jitter single photon detectors, such sources allow for the implementation of quantum communication protocols without any active synchronization or path length stabilization. A Hong–Ou–Mandel (HOM)-dip with photons from two autonomous CW sources has been realized demonstrating the setup's stability and performance.
This paper reports a novel single mode source of narrow-band entangled photon pairs at telecom wavelengths under continuous wave excitation, based on parametric down conversion. For only 7 mW of pump power it has a created spectral radiance of 0.08 pairs per coherence length and a bandwidth of 10 pm (1.2 GHz). The effectively emitted spectral brightness reaches 3.9*10^5 pairs /(s pm). Furthermore, when combined with low jitter single photon detectors, such sources allow for the implementation of quantum communication protocols without any active synchronization or path length stabilization. A HOM-Dip with photons from two autonomous CW sources has been realized demonstrating the setup's stability and performance.
Polarization entangled photon pair source is widely used in many quantum information processing applications such as teleportation, quantum communications, quantum computation and high precision quantum metrology. We report on the generation of a continuous-wave pumped 1550 nm polarization entangled photon pair source at telecom wavelength using a type-II periodically poled KTiOPO(4) (PPKTP) crystal in a Sagnac interferometer. Hong-Ou-Mandel (HOM) interference measurement yields signal and idler photon bandwidth of 2.4 nm. High quality of entanglement is verified by various kinds of measurements, for example two-photon interference fringes, Bell inequality and quantum states tomography. The source can be tuned over a broad range against temperature or pump power without loss of visibilities. This source will be used in our future experiments such as generation of orbital angular momentum entangled source at telecom wavelength for quantum frequency up-conversion, entanglement based quantum key distributions and many other quantum optics experiments at telecom wavelengths.
Quantum information protocols tend to involve more and more entangled photon pairs, for enabling advanced quantum tasks. To compensate for the low success efficiency of these protocols, one can increase the repetition rate of the emitted pairs, up to current telecom standard (40 GHz). In this context, we propose a realization of ultra-fast photon pair sources, intended for either heralded quantum state engineering or entanglement swapping at telecom wave- length. In this paper, we present preliminary results consisting of a two-photon interference experiment using four photons where the achieved raw visibility of the Hong-Ou-Mandel (HOM) dip exceeds 98.6 %. The interfering photons are generated through spontaneous parametric down conversion process (SPDC) in two independent, separate, periodically poled lithium niobate (PPLN) waveguides.
Hong-Ou-Mandel (HOM) interferometry with entangled photons exhibits distinctive quantum features. By introducing frequency entanglement (discrete-color entangled states) into HOM interference, the characteristic HOM dip is modulated by sinusoidal fringes, which significantly enhance the sensitivity of HOM sensors. The frequency-entangled photon sources demonstrated to date rely on non-resonant parametric down-conversion (PDC), which limits the photon coherence length and, consequently, restricts the sensing dynamic range to the sub-millimeter scale. In this work, we demonstrate narrowband frequency-entangled photon source based on resonant PDC in a crystalline whispering gallery mode resonator. The MHz-level spectral bandwidth of photons enables a meter-scale dynamic range. With highly nondegenerate frequency-entangled photon pairs featuring a 96 THz frequency detuning, we observe high-contrast quantum beating with sub-picosecond resolution in the HOM experiment. Our WGMR-based frequency-entangled photon source has potential applications in quantum metrology and quantum information processing.
Hong–Ou–Mandel (HOM) interferometry with entangled photons exhibits distinctive quantum features. By introducing frequency entanglement (discrete-color entangled states) into HOM interference, the characteristic HOM dip is modulated by sinusoidal fringes, which significantly enhances the sensitivity of HOM sensors. The frequency-entangled photon sources demonstrated to date rely on non-resonant parametric down-conversion (PDC), which limits the photon coherence length and, consequently, restricts the sensing dynamic range to the millimeter scale. In this work, we demonstrate narrowband frequency-entangled photon source based on resonant PDC in a crystalline whispering gallery mode resonator. The MHz-level spectral bandwidth of photons enables a meter-scale dynamic range. With highly nondegenerate frequency-entangled photon pairs featuring a 96 THz frequency detuning, we observe high-contrast quantum beating with sub-picosecond resolution in the HOM experiment. Our WGMR-based frequency-entangled photon source has potential applications in quantum metrology and quantum information processing.
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.