Heralded quasi-deterministic entanglement sources based on spontaneous parametric down-conversion

TL;DR

This paper introduces a double-heralding method for creating heralded entangled photon pairs via SPDC, optimizing resource efficiency and enabling quasi-deterministic long-range entanglement distribution with realistic detector considerations.

Contribution

The work presents a novel double-heralding technique that reduces resources and enhances efficiency over previous schemes for entangled photon pair generation.

Findings

Achieves resource-efficient entanglement with fewer sources and detectors.

Provides analytical expressions for pair probability and fidelity with realistic detector models.

Demonstrates potential for integration into photonic circuits for scalable quantum networks.

Abstract

A double-heralding technique is presented for producing heralded entangled photon pairs from spontaneous parametric down-conversion (SPDC). Compared to the swap-heralded schemes studied in previous cascaded SPDC and zero-added-loss multiplexing (ZALM) proposals, this double-heralding technique is found to yield the most resource-efficient implementation in terms of minimizing the total number of sources and detectors required to achieve a specified rate and fidelity. This is achieved by reducing the number of modes and mode-sorting optics needed on the heralding path. Specifically, by immediately detecting any two signal photons from an array of down-converters, the corresponding idler photons can be projected onto an anti-correlated pair state which is shown to be unitarily equivalent to the state produced by swap-heralded sources, and hence can be used directly for long-range entanglement distribution in a ZALM architecture. Quasi-deterministic operation through two distinct multiplexing techniques is analyzed. The analysis derives expressions for the heralded pair probability and fidelity assuming realistic detectors with losses, dark counts, and partial photon number resolution (PNR), providing a framework for implementation of the source on a photonic integrated circuit (PIC).