Generation of spectrally factorable photon pairs via multi-order quasi-phase-matched spontaneous parametric downconversion

TL;DR

This paper demonstrates a method to generate spectrally factorable photon pairs in the telecom band using multi-order quasi-phase-matching in SPDC, achieving over 95% photon purity for quantum information applications.

Contribution

The authors experimentally realize a technique to produce highly factorable photon pairs by shaping the nonlinear profile of a crystal with standard poling, approximating the phase-matching function to a Gaussian.

Findings

Photon pairs are highly factorable with >95% single-photon purity.

The phase-matching function can be approximated to a Gaussian form.

The method is applicable in the telecom band for quantum information.

Abstract

For advanced quantum information technology, sources of photon pairs in quantum mechanically factorable states are of great importance for realizing high-fidelity photon-photon quantum gate operations. Here we experimentally demonstrate a technique to produce spectrally factorable photon pairs utilizing multi-order quasi-phase-matching (QPM) conditions in spontaneous parametric downconversion (SPDC). In our scheme, a spatial nonlinearity profile of a nonlinear optical crystal is shaped with current standard poling techniques, and the associated phase-matching function can be approximated to a Gaussian form. By the measurement of a phase-matching function and the second-order autocorrelation function, we demonstrate that telecom-band photon pairs produced by our custom-poled crystal are highly factorable with > 95% single-photon purity.