Integrated quantum buffers for photonic quantum computing

About the project

Photonic quantum computers require the ability to temporarily store photons while measurements and feed-forward operations are performed. This project will develop integrated quantum buffers by combining rare-earth-ion-doped crystals with silicon nitride photonic circuits, replacing bulky optical-fibre delays with compact devices suitable for scalable photonic quantum processors.

Integrated photonics is a promising platform for large-scale quantum computing, enabling photon sources, optical circuits and detectors to be realised on a single chip. However, photons cannot simply be stopped while a quantum processor decides what to do next. Current systems route photons off-chip through hundreds of metres of optical fibre to provide the delays needed for measurement and feed-forward. As processors scale, these bulky fibre buffers present a major obstacle to fully integrated photonic quantum computers.

To overcome this challenge, this project will develop compact quantum buffers by integrating rare-earth-ion-doped crystals with silicon nitride (SiN) photonic circuits. You'll investigate thulium-doped yttrium aluminium garnet (TmYAG), using its exceptional optical coherence and controllable absorption to temporarily store GHz-bandwidth photons. The aim is to realise microsecond-scale delays within a millimetre-scale integrated device, replacing hundreds of metres of optical fibre.

You'll gain hands-on experience in cryogenic quantum optics, rare-earth-ion spectroscopy, integrated photonics and single-photon experiments. You'll develop atomic frequency comb quantum buffers, characterise their efficiency and coherence, and ultimately interface the devices with integrated single-photon sources. The project also provides opportunities to explore electrically controlled, on-demand photon retrieval.

You'll work within a multidisciplinary team spanning quantum memories and integrated photonics, with access to Southampton’s quantum optics laboratories and nanofabrication facilities. The project has strong links with the UK quantum industry, including ORCA Computing and Duality Quantum Photonics, providing opportunities to understand how these technologies could be translated into future photonic quantum processors.

Dr Patrick Ledingham PhD

• Quantum light-matter interactions
• Alkali vapour quantum memories
• Rare-earth-ion quantum memories

Supervisors

• Supervisors: Dr Alberto Politi Associate Professor

Dr Alberto Politi

• Dr Alberto Politi: Associate Professor

Entry requirements

You must have at least a UK 2:1 honours degree or its international equivalent .

Fees and funding

Funding is available on a competitive basis through the EPSRC Centre for Doctoral Training in Quantum Technology Engineering at the University of Southampton.

UK students receive a 4 year UKRI TechFirst tax-free stipend of £30,000 per year. Studentships at the UKRI minimum rate are available for EU, Horizon Europe and International students.

Overseas students who have or are seeking external funding are welcome to apply.

While undertaking your research project, you'll also receive substantial training in scientific, technical and commercial skills.

How to apply

Apply now

Please apply via the online portal and select:

Applications should include:

• Academic year: 2027/28
• If you will be full time or part time
• Faculty: Engineering and Physical Sciences
• Search for PhD Quantum Tech Eng
• Add the name of the supervisor in section 2 of the application
• your CV (resumé)
• 2 academic references
• degree transcripts and certificates to date

Faculty of Engineering and Physical Sciences

For questions about applying, email the Centre for Doctoral Training in Quantum Technology Engineering (qte@soton.ac.uk) .

Project leader

For an initial conversation, email Dr Patrick Ledingham (P.Ledingham@soton.ac.uk) .

Research areas