Southwest Quantum Information and Technology

Heralded-multiplexed high-efficiency cascaded source of dual-rail polarization-entangled photon pairs using spontaneous parametric down conversion

Presenting Author: Prajit Dhara, University of Arizona
Contributing Author(s): Spencer J. Johnson, Christos N. Gagatsos, Paul G. Kwiat, Saikat Guha

Deterministic sources of high-fidelity entangled qubit pairs encoded in the dual-rail photonic basis are a key enabling technology of many applications of quantum information processing, including high-rate high-fidelity quantum communications over long distances. The most popular and mature sources of such photonic entanglement, e.g., those that leverage spontaneous parametric down conversion (SPDC) generate an entangled quantum state that contains contributions from high-order photon terms that lie outside the span of the dual-rail basis, which is detrimental to most applications. One often uses low pump power to mitigate the effects of those high-order terms. However that reduces the pair generation rate, and the source becomes inherently probabilistic. We investigate a cascaded source that performs a linear-optical entanglement swap between two SPDC sources, to generate a heralded photonic entangled state that has a higher fidelity (to the ideal Bell state) compared to a free-running SPDC source. Further, with the Bell swap providing a heralding trigger, we show how to build a multiplexed source, which despite reasonable switching losses and detector loss and noise, yields a Fidelity versus Success Probability trade-off of a high-efficiency source of high-fidelity dual-rail photonic entanglement. We find however that there is a threshold of 1.5dB of loss per switch, beyond which multiplexing hurts the Fidelity versus Success probability.

Read this article online: https://arxiv.org/abs/2107.14360

(Session 5 : Thursday from 12:00pm-2:00 pm)