The Hub's work around photonics for quantum computing takes place at the universities of Bristol, Bath and Cardiff, along with Imperial College, London.
Our teams at Bristol and Imperial are largely working on developing quantum simulators, mature technologies such as integrated photonics and optical fibres, on addressing problems related to molecular dynamics, that will one day allow us to design new materials and cleaner sources of fuel.
At Bath and Cardiff Hub researchers are developing deeper photonic technologies such as single photon sources and quantum memories. They are working towards interfacing a single photon source and a quantum memory.
An important application for photonics is in simulating quantum chemistry. For example, the task of Gaussian Boson Sampling involves interfering squeezed states of light in an interferometer and measuring photons at the outputs. Depending on what interferometer and states of light are used, the output statistics can be used to sample Franck-Condon factors for vibronic transitions of molecules.
A key process of industrial interest is steam reformation: methane and water react to produce hydrogen. There is strong experimental evidence that specific excitation of vibrational modes increases the yield. We want to simulate this on a photonic chip using photons to mimic the bosonic behaviour of phonons.
Challenges
A large number of indistinguishable photons are required for high quality interference.
Low losses are vital to be able to simulate large number of modes.
Reconfigurability of optical circuits for accurate control of large number of modes and ability to dial in different chemical conditions.
Interfacing micropillar quantum dots with fibre and quantum memories (Bath/Cardiff)
Background
Quantum dots are a promising platform for generating many high-quality photons, but their emission wavelength is typically not compatible with telecom fibres or atomic memories.
Aim to use optically-driven Bragg-scattering four-wave mixing for ultratunablefrequency conversion up to 1550nm for low-loss propagation in fibre. Additionally, conversion down to 780nm to interface with ORCA Rb memory would unlock potential for multiplexing.
Challenges
Efficient out-coupling of quantum dot microcavity emission into a microstructured fibre.
Re-timing/routing of photons emitted from InAs/GaAs dot via optically-driven Bragg scattering requires high conversion efficiencies.
New simulable systems for photonics (Imperial)
Background
We are working to support efforts to scale up demonstrations of Gaussian Boson Sampling using photon-number resolving detectors.
Investigating new systems amenable to photonic simulation, such as boson-fermion couplings in high-temperature superconductors.
Simulating tensor networks using interference of time-bin encoded photons in a reconfigurable interferometer.
Challenges
As with Bristol's work on programmable quantum photonic silicon devices, these require large numbers of high-quality photons interfering in a reconfigurable interferometer.
Identification of efficient encoding schemes for coupled systems of single and/or mixed symmetry using photons, with assessment of role of imperfections and scalability.
