Producing high fidelity single photons with optimal brightness via waveguided parametric down-conversion

TL;DR

This paper demonstrates how spectral filtering in waveguided parametric down-conversion can produce high-fidelity single photons with optimal brightness, advancing quantum photonics applications.

Contribution

It introduces an optimized method for generating high-fidelity single photons by spectral filtering in waveguided PDC, improving state purity and brightness.

Findings

Achieved a 78% fidelity of the single-photon state.

Showed reduction of mixedness through spectral filtering.

Validated the approach via quantum interference measurements.

Abstract

Parametric down-conversion (PDC) offers the possibility to control the fabrication of non-Gaussian states such as Fock states. However, in conventional PDC sources energy and momentum conservation introduce strict frequency and photon number correlations, which impact the fidelity of the prepared state. In our work we optimize the preparation of single-photon Fock states from the emission of waveguided PDC via spectral filtering. We study the effect of correlations via photon number resolving detection and quantum interference. Our measurements show how the reduction of mixedness due to filtering can be evaluated. Interfering the prepared photon with a coherent state we establish an experimentally measured fidelity of the produced target state of 78%.