Enabling quantum entanglement distribution with photonic crystal fibre

The University of Bath is inviting applications for the following PhD project commencing on 30 September 2024 under the supervision of Dr Alexander Davis and Prof William Wadsworth in the Department of Physics.

This project will be funded by the EPSRC Quantum Technologies Doctoral Training Partnership (DTP) – for more information about eligibility for funding, please see the Funding Notes section below.

Overview of the Research:

Quantum entanglement distributed over optical fibre links is critical for technologies such as quantum cryptography and distributed quantum computing. The range of current devices is hampered by losses in available fibre. Classical network repeaters (where the signal is simply measured, electronically processed and re-emitted) cannot be used in quantum networks, because measurement-induced wavefunction collapse destroys the coherences that give quantum technologies their usefulness. So-called quantum repeaters provide a solution by successively entangling subsections (“elementary links”) of the interconnector by quantum teleportation.

Losses over each elementary link limit the eventual end-point entanglement, so a few high-quality entangled states must be prepared from many lossy attempts. This process, involving incomplete quantum measurements on the received signal, is known as entanglement distillation, and is necessary for quantum networks to scale much beyond a few tens of kilometres. A practical approach is heralded photon addition, where the attenuated signal is used to stimulate photon pair production. The detection of a successful pair generation event both adds a photon to the signal and projects the received signal into a more highly entangled state.

The University of Bath is a global centre of expertise in photonic crystal fibre (PCF) and its applications in quantum technologies. The University operates its own fibre fabrication facility, giving our researchers the opportunity to develop and test novel fibre designs in-house, as well as state-of-the-art superconducting nanowire single-photon detectors (SNSPDs). In this project, we will design and build a quantum optical transmitter, or entangled beam source, using PCF. Using the same fibre and our SNSPDs, we will also build a photon addition gate to realise distribution and distillation of quantum entanglement over long distances. This project will present the student with exciting opportunities to investigate both emerging quantum technologies and fundamental questions in quantum mechanics.

Project keywords: entanglement, quantum technologies, photonics, quantum optics, nonlinear optics, quantum networks, photonic crystal fibre

Candidate Requirements:

Applicants should hold, or expect to receive, a First Class or high Upper Second Class UK Honours degree (or the equivalent) in physics or a closely allied subject. A master’s level qualification would also be advantageous.

Non-UK applicants must meet our English language entry requirement.

Enquiries and Applications:

Applicants are encouraged to contact Dr Alexander Davis (email: aocd20@bath.ac.uk) or Prof William Wadsworth (email: pyswjw@bath.ac.uk) before applying to find out more about the project and to discuss their suitability for the role.

Formal applications should be made via the University of Bath’s online application form for a PhD in Physics.

In the ‘Funding your studies’ section of the application form, please select ‘EPSRC DTP’ from the first drop-down menu. In the ‘Your PhD project’ section, please quote the project title and lead supervisor’s name in the appropriate fields. Failure to complete these steps will cause a delay in processing your application and may cause you to miss the deadline.

More information about applying for a PhD at Bath may be found on our website.

NOTE: Applications may close earlier than the advertised deadline if a suitable candidate is found; therefore, we recommend that you contact Dr Alex Davis prior to applying and submit your formal application as early as possible.

Equality, Diversity and Inclusion:

We value a diverse research environment and aim to be an inclusive university, where difference is celebrated and respected. We welcome and encourage applications from under-represented groups.

If you have circumstances that you feel we should be aware of that have affected your educational attainment, then please feel free to tell us about it in your application form. The best way to do this is a short paragraph at the end of your personal statement.