Telecom C‐Band Source of Triggered Polarization‐Entangled Photon Pairs Combining High Coincidence Rates, Fidelities and Single‐Photon Purity

Many protocols of future quantum networks rely on the availability of entangled qubits which enable links among remotenodes due to their unique properties. Therefore, the efficient generation of entangled photons constitutes a key goal toward theimplementation of such quantum networks. However, currently available sources are bound by intrinsic limitations, as for instanceprobabilistic nature of emission. Deterministic quantum emitters pose a potential solution for this issue, however, the maturity oftheir device platforms still needs to be improved for truly on-demand emission. While record efficiencies are currently found atnear-infrared wavelengths, sources at telecommunication wavelengths will likely be the ideal choice for quantum networks. Thatmotivates the development of efficient sources of entangled photons in the telecom regime. This work addresses that challengepresenting a telecom C-band source of polarization entangled photons based on semiconductor quantum dots incorporated ina planar cavity structure. In this way, triggered emission of entangled photon pairs with a coincidence rate of 201 ± 13 kcps(biexciton/exciton fiber-coupled single-photon count rates of 5.04 ± 0.16 Mcps/1.97 ± 0.06 Mcps) combined with 𝑔$^{(2)}$ (0) valuesof 0.009 ± 0.001/0.015 ± 0.001 is achieved. ... mehrFull quantum state tomography of the two-photon state demonstrates simultaneouslyentanglement fidelities of up to 0.964 ± 0.001 to the Φ$^+$ Bell state.