Methods towards photonic quantum error detection and correction

A key challenge in quantum computing involves dealing with errors which may arise from environmental noise or imperfections in the hardware. Error mitigation and correction strategies are essential to the development of practical quantum computing devices. In recent years, photonic quantum computing has emerged as a promising platform for quantum computing and demonstrating a genuine quantum advantage. Quantum states of light (QSoL) are robust to environmental noise and can be easily manipulated and measured using simple optical components at room temperature. Additionally, QSoL can be transmitted over long distances using optical fibres, which makes them an attractive option for quantum communication and networking.

Errors can manifest in many ways, for example, from imperfect state preparation, improper circuit operations and photon loss. The latter—photon loss—is perhaps the most challenging source of error to overcome in photonic quantum information processing. Photon loss can lead to degradation or an immediate loss of the QSoL. Photonic implementations usually rely on heterogeneous integration of optimised components (sources, circuits, and detectors) with dissimilar optical properties which often lead to photon loss due to mode-mismatch. Furthermore, imperfect manufacture of optical components can also contribute to loss. Aside from loss, the optical components, which form the building blocks of quantum circuits, perform the desired operation to within a limited precision causing errors in quantum algorithms. Thus, mitigating or correcting these errors is critical for the development of practical photonic quantum computers.

Error-mitigation techniques may involve modifying the quantum circuit to reduce the impact of errors on the computation or performing several measurements and post-processing the outcomes to infer what the error-free result should be. One approach to error-correction involves using quantum error-correcting codes (ECCs). ECCs involve encoding the quantum state in a larger Hilbert space, which is protected against certain types of errors. Bosonic ECCs, using non-Gaussian QSoL, utilise the full harmonic-oscillator nature of light meaning that a single QSoL can encode the logical information and still have the redundancy necessary for error-correction.

RUQu is seeking a talented and motivated student to undertake research in photonic quantum information technologies with a focus on error handling in both near-term quantum computers such as Gaussian Boson Samplers, and future universal photonic quantum computers. The research will be experimental in nature, although a proclivity for theoretical quantum optics will be deemed an advantage.

The project is supported by a total of £1.97 million UK Research & Innovation and UK National Quantum Technologies programme funding and will involve close collaboration with partners in both academia and industry.

The successful applicant will perform experiments to demonstrate error mitigation and error-correction. They will work as part of a team to translate theoretical proposals into experimental demonstrations. Specifically, they will:

  • Build high-gain squeezed light sources based on bulk optics and waveguides in non-linear materials.
  • Learn how to design, characterise, and use photonic integrated circuits in materials such as silicon, silicon nitride, and lithium niobate.
  • Work with collaborators in industry and academia to mitigate loss in integrated photonic circuits. They will be involved in developing low-loss photonic interconnects which facilitate the transmission of QSoL between sources, circuits, and detectors.
  • Investigate error mitigation strategies for noisy intermediate-scale quantum computing approaches such as Gaussian Boson Sampling.
  • Study the suitability of these strategies for specific use cases and applications.
  • Use squeezed light sources and photon-number resolving detection to engineer non-Gaussian QSoL relevant to Bosonic error-correction codes.

Aside from these research goals, the successful student will be supported in the development of their research career. The goal of the PhD is to train the student to become an independent researcher. This training will be delivered through daily mentorship by senior PhD students, postdocs, and their PhD supervisor and supplemented by training courses hosted at Imperial College London. The student will:

  • Learn to take initiative in the planning of research.
  • Learn to develop ideas and to communicate them within the project.
  • Learn to prepare effective and engaging presentations in oral and poster formats.
  • Represent RUQu at national and international conferences and present findings to colleagues and attendees.
  • Learn to draft publications and prepare them for submission to peer-reviewed journals.
  • Contribute to the drafting of proposals for research grants.
  • Learn how to supervise junior students (undergraduate and masters students) on small research projects.
  • Learn how to manage laboratory resources and contribute to the daily operations of the group and laboratory.


For futher information please contact Dr Raj Patel.