Generation of entanglement between a highly wave-packet-tunable photon and a spin-wave memory in cold atoms

TL;DR

This paper demonstrates the control of the waveform length of a photon entangled with an atomic spin-wave memory by varying light-atom interaction time in cold atoms, enabling Bell inequality violations over a wide duration range.

Contribution

It introduces a method to control the waveform of entangled photons with atomic memories by adjusting interaction time, a novel approach in quantum network interconnectivity.

Findings

Bell inequality violations achieved for photon pulses from 40 ns to 50 μs.

Bell parameter S decreases as photon pulse duration increases.

Photon noise probability increases with pulse duration, affecting entanglement quality.

Abstract

Controls of waveforms (pulse durations) of single photons are important tasks for effectively interconnecting disparate atomic memories in hybrid quantum networks. So far, the waveform control of single photon that is entangled with an atomic memory remains unexplored. Here, we demonstrated control of waveform length of the photon that is entangled with an atomic spin-wave memory by varying light-atom interaction time in cold atoms. The Bell parameter S as a function of the duration of photon pulse is measured, which shows that violations of Bell equality can be achieved for the photon pulse in the duration range from 40 ns to 50 us, where, S=2.64+/-0.02 and S=2.26+/-0.05 for the 40-ns and 50-{\mu}s durations, respectively. The measured results show that S parameter decreases with the increase in the pulse duration. We confirm that the increase in photon noise probability per pulse with the pulse-duration is responsible for the S decrease.