Ultrabright narrow-band telecom two-photon source for long-distance quantum communication

TL;DR

This paper presents an ultrabright, narrow-band two-photon source at 1.5 μm for long-distance quantum communication, achieving unprecedented spectral brightness and linewidth, suitable for quantum repeater applications.

Contribution

The work introduces a highly efficient two-photon source with record spectral brightness and linewidth at telecom wavelengths, advancing quantum communication technology.

Findings

Achieved a cavity enhancement factor of 4.06×10^4.

Measured a linewidth of 2.4 MHz, the narrowest in this band.

Reported the highest spectral brightness of 3.94×10^5 pairs/(s·MHz·mW).

Abstract

We demonstrate an ultrabright narrow-band two-photon source at the 1.5 -\mu m telecom wavelength for long-distance quantum communication. By utilizing a bow-tie cavity, we obtain a cavity enhancement factor of $4.06\times 10^4$. Our measurement of the second-order correlation function $G^{(2)} ({\tau})$ reveals that the linewidth of $2.4$ MHz has been hitherto unachieved in the 1.5 -\mu m telecom band. This two-photon source is useful for obtaining a high absorption probability close to unity by quantum memories set inside quantum repeater nodes. Furthermore, to the best of our knowledge, the observed spectral brightness of $3.94\times 10^5$ pairs/(s$\cdot$MHz$\cdot$mW) is also the highest reported over all wavelengths.