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Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)

Enabling Hybrid Two-Photon Interference with a Time Lens

Jan Krzyżanowski, Jerzy Szuniewicz, Sanjay Kapoor, Filip Sośnicki, Michał Karpiński

Published Jun 23, 2025• 0 citations
Publisher

Abstract

Single-photon indistinguishability is a crucial property for many photonic quantum technologies, as it directly affects the visibility of two-photon interference [1], which is used for entanglement swapping, quantum teleportation etc. It is critical for experiments involving quantum information exchange between two mismatched systems such as different photon source types [2] or for quantum repeaters.

DOI
10.1109/cleo/europe-eqec65582.2025.11109861

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Single-photon indistinguishability is a crucial property for many photonic quantum technologies, as it directly affects the visibility of two-photon interference [1], which is used for entanglement swapping, quantum teleportation etc. It is critical for experiments involving quantum information exchange between two mismatched systems such as different photon source types [2] or for quantum repeaters.
Two-photon interference is a cornerstone of photonic quantum technologies. However, its practical use in hybrid architectures is constrained by the need for photon indistinguishability, particularly in linewidth and the associated time scale. While narrowband filtering can improve interference visibility, it introduces significant photon loss - a critical limitation for applications. Here, we experimentally demonstrate an efficient approach to enable non-classical two-photon interference between spectral-bandwidth mismatched photons using an electro-optic time lens. We increase the visibility of Hong-Ou-Mandel (HOM) interference between spectral bandwidth mismatched photons from (31.0±1.7)%(31.0\pm1.7)\%(31.0±1.7)%, to (91.7±2.6)%(91.7\pm2.6)\%(91.7±2.6)%, with correction for accidental coincidences, achieving highly non-classical two-photon interference visibility without spectral filtering. Moreover, we demonstrate a simultaneous correction of the central wavelength mismatch of ±1.1\pm1.1±1.1 nm, while maintaining the non-classical interference visibility. This result opens the possibility to efficiently integrate quantum systems operating at different time scales for hybrid quantum communication, teleportation, entanglement swapping, distributed sensing, and hybrid quantum computing.
A key requirement for implementing photonic quantum information networks is the mutual two-photon interference between photons emitted by spatially separated quantum light sources. In order to up-scale such networks, the deterministic fabrication of efficient sources of single and indistinguishable photons is of crucial importance. So far, few experiments reported on two-photon interference (TPI) from spatially separated QD-based single photon sources, which is required for entanglement swapping, and deterministic sources have been applied only recently [1]. However, narrowband enhancement of photon extraction in high-Q microcavities hinders their application for advanced quantum communication schemes based on polarization entangled photon pairs from the biexciton-exciton radiative cascade.
Abstract Indistinguishability of single photons from independent sources is critically important for scalable quantum technologies. We provide a comprehensive comparison of single-photon indistinguishability of different kinds of cavity quantum electrodynamics (CQEDs) systems by numerically simulating Hong–Ou–Mandel two-photon interference. We find that the CQED system using natural atoms exhibits superiority in indistinguishability, benefiting from the inherently identical features. Moreover, a Λ − type three-level atom shows essential robustness against variation of various system parameters because it exploits the two ground states with considerably smaller decay rates for single-photon generation. Furthermore, a machine learning-based framework is proposed to significantly and robustly improve single-photon indistinguishability for two non-identical CQED systems. This work may pave the way for designing and engineering reliable and scalable photon-based quantum technologies.
Entanglement swapping and heralding are at the heart of many protocols for distributed quantum information. For photons, this typically involves Bell-state measurements based on two-photon interference effects. In this context, hybrid systems that combine high rate, ultrastable, and pure quantum sources with long-lived quantum memories are particularly interesting. Here, we develop a theoretical description of pulsed two-photon interference of photons from dissimilar sources to predict the outcomes of second-order cross-correlation measurements. These are directly related to, and hence used to quantify, photon indistinguishability. We study their dependence on critical system parameters such as quantum state lifetime and emission frequency, and quantify the impact of time jitter, pure dephasing, and spectral wandering. We show that for a fixed lifetime of one of the two emitters, for each frequency detuning there is an optimal lifetime of the second emitter that leads to the highest photon indistinguishability. Expectations for different hybrid combinations involving III-V semiconductor quantum dots, color centers in diamond, atom-scale defects in two-dimensional materials and neutral atoms are quantitatively compared for real-world system parameters. Our work provides a theoretical basis for the treatment of dissimilar emitters and enables assessment of which imperfections can be tolerated in hybrid photonic quantum networks.