Work

Coherent temporal filtering of multimode parametric down-conversion using a quantum pulse gate

Year: 2026

Type: preprint

Abstract: Spectrally pure and indistinguishable single photons are essential for quantum network platforms, where high-visibility interference underpins many quantum information protocols. However, most practical single-photon sources emit spectrally multimode states with reduced purity. Conventional spectral intensity filtering can partially improve purity but cannot select a well-defined temporal mode (TM). Here, we demonstrate coherent temporal filtering of a multimode parametric down-conversion (PDC) source using a quantum pulse gate (QPG) and benchmark its performance against conventional intensity filtering. The generated PDC photons exhibit strong spectral correlations, rendering extraction of pure heralded photons from the pair a challenge. We demonstrate that QPG filtering consistently generates heralded photons with purities above 0.90 regardless of the filter shape. Contrariwise, using spectral intensity filters yields mixed photons. Photon purities are probed with chronocyclic Q-function tomography. Furthermore, we demonstrate the versatility of QPG filtering by extracting structured TMs, including superposition of picosecond time bins. These results establish the QPG as a practical coherent filtering tool for quantum network applications.

Source: arXiv (Cornell University)

DOI: 10.48550/arxiv.2608.12544

Authors: Bhattacharjee, Abhinandan, Folge, Patrick, Serino, Laura, Lengeling, Sebastian, Brecht, Benjamin, Silberhorn, Christine

Institutions: Paderborn University, The University of Queensland

Topic: Quantum Information and Cryptography

Subfield: Artificial Intelligence

Field: Computer Science

Domain: Physical Sciences

Open Access status: green

Funders: European Commission, HORIZON EUROPE Framework Programme

Awards: G8534662092, Spectral-Temporal Metrology with Tailored Quantum Measurements

OpenAlex ID: W7203468635

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