Abstract
We report a bright source of polarization-entangled photon pairs using spontaneous parametric down-conversion (SPDC) in a 10 mm long type-II PPKTP crystal pumped by a broadband multi-mode diode laser with the coherence length of 330 μm. Ordinarily, the huge mismatch between the pump coherence length and the PPKTP length would degrade the polarization entanglement completely. By employing the universal Bell-state synthesizer scheme, we remove the spectral/temporal distinguishability of the biphoton amplitudes entirely to recover high-visibility and high-fidelity two-photon polarization entanglement. The pair detection rates are 7,000 pairs/mW via single-mode fibers (with 99.2% fidelity) and 90,900 pairs/mW via multi-mode fibers (with 96.8% fidelity). We also analyze the scheme theoretically to show the effect of broadband multi-mode pumping on the phase matching condition of the type-II PPKTP.
Highlights
A source of polarization-entangled photons is an essential resource in various quantum information applications, including quantum computing, quantum teleportation, and quantum communication
Solid state and atomic systems have recently shown the feasibility of entangled photon generation [1,2,3], spontaneous parametric down-conversion (SPDC) in a nonlinear optical crystal is by far the most versatile source of entangled photons due to comparably high generation rates and wide varieties of photonic quantum states SPDC can generate with high purity and fidelity
We report a bright source of polarization-entangled photon pairs using a 10 mm long type-II PPKTP pumped by a broadband multi-mode cw diode laser with the coherence length of 330 μm
Summary
A source of polarization-entangled photons is an essential resource in various quantum information applications, including quantum computing, quantum teleportation, and quantum communication. The first scheme made use of non-collinear type-I SPDC pumped by a monochromatic continuous-wave (cw) laser and a non-polarizing beam splitter for quantum interference of the photon pairs [4]. The schemes for generating polarization entangled photon pairs based on the monochromatic cw laser pumped SPDC include non-collinear type-II SPDC [5, 6], collinear type-II SPDC [7], two non-collinear type-I SPDC [8, 9], two collinear type-I SPDC [10,11,12], beamlike type-II SPDC [13,14,15,16], overlapping type-II emission cones [17], linear double pass scheme [18], etc
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