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 3.9×105 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.
Highlights
The detection signals are sent to a time to amplitude converter (TAC) with a nominal temporal resolution of 45.5 ps
The two output modes are each connected to a superconducting single photon detector (SSPD) as shown in figure 3, and for the case where both SSPDs click, the arrival time difference τ of the photons is recorded by a time to digital converter (TDC), connected to a computer
We have realized a set-up of two autonomous continuous wave (CW) photon pair sources with long coherence times in combination with new-generation high resolution detectors
Summary
The different components of our source are described in detail. Pairs of energy-time entangled photons are created by SPDC in a nonlinear crystal pumped at λp = 780 nm. The crystal is a 50 mmlong PPLN waveguide (HC Photonics). Phase matching is such that SPDC produces degenerate pairs of signal and idler photons at 1560 nm; with a spectral distribution of λ0 = 80 nm. The created photons have the same polarization and exit the PPLN waveguide collinearly. They are coupled into a standard optical single mode fibre with an efficiency of 30%.
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