Spectral compression of single photons

TL;DR

This paper demonstrates a method to compress and tune the spectral bandwidth of single photons using sum-frequency generation with chirped pulses, enabling advanced quantum information processing and interfacing.

Contribution

It introduces a novel spectral compression technique for single photons with tunability over a broad range, facilitating coherent quantum interfaces.

Findings

Bandwidth compression by a factor of 40

70-fold tunability of photon bandwidth

Enables ultrafast timing and waveform generation

Abstract

Photons are critical to quantum technologies since they can be used for virtually all quantum information tasks: in quantum metrology, as the information carrier in photonic quantum computation, as a mediator in hybrid systems, and to establish long distance networks. The physical characteristics of photons in these applications differ drastically; spectral bandwidths span 12 orders of magnitude from 50 THz for quantum-optical coherence tomography to 50 Hz for certain quantum memories. Combining these technologies requires coherent interfaces that reversibly map centre frequencies and bandwidths of photons to avoid excessive loss. Here we demonstrate bandwidth compression of single photons by a factor 40 and tunability over a range 70 times that bandwidth via sum-frequency generation with chirped laser pulses. This constitutes a time-to-frequency interface for light capable of converting time-bin to colour entanglement and enables ultrafast timing measurements. It is a step toward arbitrary waveform generation for single and entangled photons.