Abstract
We demonstrate a novel alignment-free all-fiber source for generating telecom-band polarization-entangled photon pairs. Polarization entanglement is created by injecting two relatively delayed, orthogonally polarized pump pulses into a piece of dispersion-shifted fiber, where each one independently engages in four-photon scattering, and then removing any distinguishability between the correlated photon-pairs produced by each pulse at the fiber output. Our scheme uses a Michelson-interferometer configuration with Faraday mirrors to achieve practically desirable features such as ultra-stable performance and turnkey operation. Up to 91.7% two-photon-interference visibility is observed without subtracting the accidental coincidences that arise from background photons while operating the source at room temperature.
Highlights
Quantum entanglement is a key resource in most quantum-communication protocols such as quantum cryptography [1] and quantum teleportation [2]
They are injected into a piece of optical fiber where each pump pulse independently engages in four-photon scattering (FPS)
As in other entangled-photon sources, pump power can be tuned to a level such that with high probability only one photon pair is emitted from the two FPS processes
Summary
Quantum entanglement is a key resource in most quantum-communication protocols such as quantum cryptography [1] and quantum teleportation [2]. Before leaving the source fiber, the FPS processes originating from each pump pulse with definite polarization are coherently combined while removing information such as the relative time delay This makes the created photon pairs from the two FPS processes indistinguishable from each other and polarization entanglement is established. In Ref. 5 a free-space Michelson interferometer is employed for preparing 30 ps relative delay between the two orthogonally polarized 5-ps-duration pump pulses This time delay is erased by passing the signal-idler photon pairs, which are generated in a 300-mlong fiber Sagnac loop made of dispersion-shifted fiber (DSF), through 20 m of polarization maintaining fiber. Fiber-birefringence induced polarization fluctuations need to be carefully compensated before sending the photon pairs through the polarization maintaining fiber for accurately removing the time delay This scheme is too complicated for practical usage. The scheme utilizes fiber-pigtailed optical components which have been fully integrated for turnkey operation
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