Polarization-entangled mode-locked photons from cavity-enhanced spontaneous parametric down-conversion

Wang, Haibo; Horikiri, Tomoyuki; Kobayashi, Takayoshi

doi:10.1103/physreva.70.043804

Cited by 68 publications

(57 citation statements)

References 18 publications

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“…The reduction in spectral bandwidth is compensated by the enhancement in the efficiency of the photon pair generation due to the cavity resonance. Without further filtering, the output of the cavity is spectrally multimode (Kuklewicz et al, 2006;Scholz et al, 2009;Wang et al, 2004;Wolfgramm et al, 2008). Ideally, a single cavity mode should be selected, such that the bandwidth of the parametric light is given by the width of the cavity mode.…”

Section: Narrow Band Photon Pair Sources Based On Parametric Down Conmentioning

confidence: 99%

Quantum repeaters based on atomic ensembles and linear optics

et al. 2011

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The distribution of quantum states over long distances is limited by photon loss. Straightforward amplification as in classical telecommunications is not an option in quantum communication because of the no-cloning theorem. This problem could be overcome by implementing quantum repeater protocols, which create long-distance entanglement from shorter-distance entanglement via entanglement swapping. Such protocols require the capacity to create entanglement in a heralded fashion, to store it in quantum memories, and to swap it. One attractive general strategy for realizing quantum repeaters is based on the use of atomic ensembles as quantum memories, in combination with linear optical techniques and photon counting to perform all required operations. Here we review the theoretical and experimental status quo of this very active field. We compare the potential of different approaches quantitatively, with a focus on the most immediate goal of outperforming the direct transmission of photons.

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Section: Narrow Band Photon Pair Sources Based On Parametric Down Conmentioning

confidence: 99%

Quantum repeaters based on atomic ensembles and linear optics

et al. 2011

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“…Experimentally, Ou et al [11] has realized a type-I source, in which the two photons generated have the same polarization, making it very difficult to generate entanglement. Wang et al [13] made a further step by putting two type-I nonlinear crystals within a ring cavity to generate polarization entanglement, but unfortunately the output is multi-mode which does not fit the requirement of an atomic quantum memory. While, a type-II configured source (down-converted photons have different polarizations) is more preferable for the ease of generating polarization entanglement, compared with a type-I source.…”

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Generation of Narrow-Band Polarization-Entangled Photon Pairs for Atomic Quantum Memories

et al. 2008

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We report an experimental realization of a narrow-band polarization-entangled photon source with a linewidth of 9.6 MHz through cavity-enhanced spontaneous parametric down-conversion. This linewidth is comparable to the typical linewidth of atomic ensemble based quantum memories. Single-mode output is realized by setting a reasonable cavity length difference between different polarizations, using of temperature controlled etalons and actively stabilizing the cavity. The entangled property is characterized with quantum state tomography, giving a fidelity of 94% between our state and a maximally entangled state. The coherence length is directly measured to be 32 m through two-photon interference.PACS numbers: 03.67. Bg, 42.65.Lm The storage of photonic entanglement with quantum memories plays an essential role in linear optical quantum computation (LOQC) [1] to efficiently generate large cluster states [2], and in long-distance quantum communication (LDQC) to make efficient entanglement connections between different segments in a quantum repeater [3]. For the atomic ensemble based quantum memories [4,5,6], typical spectrum linewidth required for photons is on the order of several MHz. While spontaneous parametric down-conversion (SPDC) is the main method to generate entangled photons [7], the linewidth determined by the phase-matching condition is usually on the order of several THz which is about 10 6 times larger, making it unfeasible to be stored. Moreover, interference of independent broad-band SPDC sources requires a synchronization precision of several hundred fs [8]. While in LDQC, for the distance on the order of several hundred km, it becomes extremely challenging for the current synchronization technology [9,10]. But for a narrowband continuous-wave source at MHz level, due to the long coherence time, synchronization technique will be unnecessary, while coincidence measurements with time resolution of several ns with current commercial singlephoton detectors will be enough to interfere independent sources.Passive filtering with optical etalons is a direct way to get MHz level narrow-band entangled photons from the broad-band SPDC source, but it will inevitably result in a rather low count rate. In contrast, cavity-enhanced SPDC [11,12] provides a good solution for this problem. By putting the nonlinear crystal inside a cavity, the generation probability for the down-converted photons whose frequency matches the cavity mode will be enhanced greatly. The cavity acts as an active filter. The frequency of the generated photons lies within the cavity mode, which can be easily set to match the required atomic linewidth. Experimentally, Ou et al.[11] has realized a type-I source, in which the two photons generated have the same polarization, making it very difficult to generate entanglement. Wang et al.[13] made a further step by putting two type-I nonlinear crystals within a ring cavity to generate polarization entanglement, but unfortunately the output is multi-mode which does not fit the requirement of an...

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“…By putting the nonlinear crystal inside a cavity, the linewidth of generated photon pairs is limited by the cavity linewidth and the generation probability for the down-converted photons whose frequency matches the cavity mode will be enhanced greatly. Significant progress has been made in this regard [19][20][21][22][23][24][25] . Recently, the generation of single-mode narrow-band polarization entangled source has been reported through cavity-enhanced SPDC [25] , and the storage of such entangled photons has been demonstrated in a cold atomic ensemble [26] In this paper, we also demonstrate a narrow-band polarization-entangled photon pairs at Rb D .…”

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confidence: 99%