Quantum Communications from Space

Quantum key distribution (QKD) is a mature quantum communication technology that aims to connect remote users with unbreakable security. It is based on optical signals that can be transmitted over various channels including optical fibre and the Earth’s atmosphere, with requirements that depend on the underlying communication channel and protocol. Earlier QKD experimental demonstrations and commercial deployments were based on point-to-point fibre optical links with quantum signals co-existing with classical data channels.

The attenuation in the fibre link limits the achievable transmission distance in a point-to-point connection. For longer transmission distances, for example at continental distances, the viability of the satellite-based quantum signal distribution (also reception) has been demonstrated. In a typical LEO satellite-to-ground link the major contribution to signal loss is from the geometrical divergence of the optical beam, of a few 10s of dB loss (In a clear sky condition, the loss from atmospheric scattering and absorption is a few dB ). Compared to 100dB loss in a 500km fibre optic channel (0.2dB/km), LEO satellite-based quantum communication clearly shows the advantage.

Most of the satellite quantum communication systems demonstrated as well as in the development phases, are based on single photon generation at the satellite and subsequent detection on the ground. The daytime ambient background light restricts the operation of such quantum satellites to the nighttime when the noise photons are at a minimal level. However, quantum communication based on coherent quantum signal modulation and shot-noise limited detection can tolerate the background noise to a comparatively higher level than the single photon detection-based systems. This enables quantum coherent communication suitable for day and night operations.

At York, we have expertise in quantum coherent communications and have built and demonstrated systems for fibre as well as for free-space channels. In this project, we will develop systems and methods for increasing the free-space transmission distance of quantum coherent communication. The prime goal of this study is to improve the link budget quantum communication system. Increasing the link budget removes the need for large aperture telescopes for signal collection, resulting in the low-cost, transportable optical ground station for space quantum communication based on coherent communication. At the same time, this study will bring the quantum payload based on coherent communication close to the commercial market.

Academic entry requirements: at least a class 2:1 MSc or MPhys degree in Physics.

How to apply:

Applicants must apply via the University’s online application system at https://www.york.ac.uk/study/postgraduate-research/apply/. Please read the application guidance first so that you understand the various steps in the application process. To apply, please select the PhD in Physics for October 2023 entry. Please specify in your PhD application that you would like to be considered for this studentship.