Entanglement Swapping for Generation of Heralded Time-Frequency-Entangled Photon Pairs

TL;DR

This paper explores entanglement swapping in the time-frequency domain using three-wave mixing to generate high-purity, heralded biphoton states, emphasizing the importance of frequency-resolving measurements for optimal results.

Contribution

It introduces a realistic model for continuous-variable entanglement swapping with pulsed pumps and analyzes the impact of herald photon frequency resolution on biphoton purity.

Findings

Frequency-resolving measurement is essential for high-purity biphotons.

A trade-off exists between entanglement swapping rate and biphoton quality.

Low-gain three-wave mixing effectively enables heralded entangled photon generation.

Abstract

Photonic time-frequency entanglement is a promising resource for quantum information processing technologies. We investigate swapping of continuous-variable entanglement in the time-frequency degree of freedom using three-wave mixing in the low-gain regime with the aim of producing heralded biphoton states with high purity and low multi-pair probability. Heralding is achieved by combining one photon from each of two biphoton sources via sum-frequency generation to create a herald photon. We present a realistic model with pulsed pumps, investigate the effects of resolving the frequency of the herald photon, and find that frequency-resolving measurement of the herald photon is necessary to produce high-purity biphotons. We also find a trade-off between the rate of successful entanglement swapping and both the purity and quantified entanglement resource (negativity) of the heralded biphoton state.