Optimizing time-entanglement between two sources

TL;DR

This paper presents a compact, spectrally and spatially minimized entangled photon source capable of generating GHZ states, with optimized coherence and high count rates for quantum communication applications.

Contribution

The authors design a source with minimal spectral and spatial entanglement and demonstrate removal of timing information to enhance entanglement coherence.

Findings

Achieved high coherence between sources via Hong-Ou-Mandel interference.

Measured a count rate of 13,600 counts/sec per mW of pump power.

Validated low multi-pair production rate with second order correlation measurements.

Abstract

We demonstrate a compact source of four entangled telecommunication wavelength photons, which is used to generate a GHZ state, with minimal spectral and spatial entanglement. The spatial and spectral degree of freedom are minimized by careful source design. To optimize the entanglement between the two sources, distinguishing temporal information must be removed. We demonstrate this high degree of coherence, between pairs of sources, by performing a Hong-Ou-Mandel measurement. This measurement enables the optical path lengths within the system to be equalized, removing timing information from photons. We also measure the second order correlation function to test the rate of multi-pair production from a single pump pulse. With these optimizations completed, we measure a count rate of 13,600 counts/s per mW of pump power.