# Quantum Storage of Frequency-Multiplexed Heralded Single Photons

## TL;DR

This paper demonstrates the quantum storage of a frequency-multiplexed heralded single photon with 15 frequency modes and 130 total modes using an integrated rare-earth doped waveguide, preserving its non-classical properties.

## Contribution

It introduces a method to store a complex, frequency-multimode single photon in a solid-state quantum memory with high mode capacity and preserves its quantum features.

## Key findings

- Successfully stored a 15-mode frequency-multimode photon
- Preserved non-classical properties after storage
- Achieved about 130 total stored modes

## Abstract

We report on the quantum storage of a heralded frequency-multiplexed single photon in an integrated laser-written rare-earth doped waveguide. The single photon contains 15 discrete frequency modes separated by 261 MHz and spaning across 4 GHz. It is obtained from a non-degenerate photon pair created via cavity-enhanced spontaneous down conversion, where the heralding photon is at telecom wavelength and the heralded photon is at 606 nm. The frequency-multimode photon is stored in a praseodymium-doped waveguide using the atomic frequency comb (AFC) scheme, by creating multiple combs within the inhomogeneous broadening of the crystal. Thanks to the intrinsic temporal multimodality of the AFC scheme, each spectral bin includes 9 temporal modes, such that the total number of stored modes is about 130. We demonstrate that the storage preserves the non-classical properties of the single photon, and its normalized frequency spectrum.