Millimetre-wave multiplexed qubit control through on-chip nonreciprocal space-time superconducting frequency multipliers

About the project

Today's quantum computers need a dedicated microwave source per qubit, a wiring bottleneck limiting scale-up. This project builds an on-chip superconducting device where a single microwave frequency source drives an entire qubit array at distinct frequencies up to the millimetre-wave range, using space-time-modulated Josephson junctions for nonreciprocal multiplexing.

Superconducting quantum processors are limited not just by qubit coherence but by wiring: each qubit typically needs its own microwave control line, and this overhead grows rapidly as processors scale toward hundreds or thousands of qubits. This project addresses that bottleneck by developing a fundamentally new class of on-chip control hardware: a nonreciprocal, space-time-modulated superconducting frequency multiplier that converts a single drive into a full comb of directionally isolated tones spanning up to millimetre-wave frequencies, with each tone addressing a different qubit, removing the need for a dedicated high-frequency source per qubit.

Building on theoretical and simulation work recently published by the supervisory team (IEEE Transactions on Antennas and Propagation), you'll take this device from simulation to hardware: developing the circuit and Hamiltonian models, designing and fabricating superconducting thin-film prototypes, and integrating them with a small array of flux-tunable transmon qubits. You'll characterise harmonic-comb generation, nonreciprocal isolation, and the resulting suppression of Purcell decay and qubit-qubit crosstalk at millikelvin temperatures, establishing whether this architecture can genuinely reduce the wiring burden of scalable quantum computing.

Dr Sajjad Taravati

• Metamaterials/metasurfaces/antennas
• Electromagnetics/telecommunications
• Superconducting quantum circuits

Entry requirements

You must have at least a UK 2:1 honours degree, or its international equivalent , in one of the following:

• quantum science
• physics
• electromagnetics
• electronic engineering
• applied mathematics

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 Sajjad Taravati (S.Taravati@soton.ac.uk) .

Research areas