Interaction of Independent Single Photons based on Integrated Nonlinear Optics

TL;DR

This paper demonstrates photon-photon interactions using integrated nonlinear optics at telecom wavelengths, advancing quantum communication by enabling efficient, room-temperature, on-chip nonlinear effects suitable for long-distance quantum networks.

Contribution

It introduces a high-efficiency nonlinear waveguide for sum-frequency generation between single photons and coherent states at telecom wavelengths, suitable for scalable quantum communication.

Findings

Successful observation of photon-photon interaction via sum-frequency generation

Use of integrated, room-temperature device compatible with quantum communication

Potential for long-distance quantum networks and device-independent quantum key distribution

Abstract

Photons are ideal carriers of quantum information, as they can be easily created and can travel long distances without being affected by decoherence. For this reason, they are well suited for quantum communication. However, the interaction between single photons is negligible under most circumstances. Realising such an interaction is not only fundamentally fascinating but holds great potential for emerging technologies. It has recently been shown that even weak optical nonlinearities between single photons can be used to perform important quantum communication tasks more efficiently than methods based on linear optics, which have fundamental limitations. Nonlinear optical effects at single photon levels in atomic media have been studied and demonstrated but these are neither flexible nor compatible with quantum communication as they impose restrictions on photons' wavelengths and bandwidths. Here we use a high efficiency nonlinear waveguide to observe the sum-frequency generation between a single photon and a single-photon level coherent state from two independent sources. The use of an integrated, room-temperature device and telecom wavelengths makes this approach to photon-photon interaction well adapted to long distance quantum communication, moving quantum nonlinear optics one step further towards complex quantum networks and future applications such as device independent quantum key distribution.