International Network on Quantum Annealing (INQA)

Quantum annealing (QA) is an application-specific alternative paradigm to universal gate-based quantum computation (GBQC). The application for which QA was originally proposed is optimisation, though more recently applications in quantum simulation and machine learning have also been proposed. QA makes less stringent demands on the coherence of the underlying qubits than does GBQC. This has enabled experimentalists to demonstrate many diverse optimisation use-case proofs of principle using QA, exploiting the superconducting flux-qubit-based annealing system developed by D-Wave Systems. Such applications include materials simulation, financial portfolio optimisation, traffic routing, fraud detection, circuit fault diagnosis and website recommendation engines.

Nevertheless at present there is scant (if any) experimental evidence of any quantum speedup for any real world application, and it is at least arguable that merely increasing the number of flux qubits in the existing hardware without any new qualitative design features will never lead to a scaling speedup. Several global collaborations have therefore been set up in the US, UK, EU and Japan to identify what qualitative features could be added to future implementations of quantum annealing devices which would enable a transformational scaling speedup (at least for some class of hard problems) by comparison with classical benchmarks.

A key discriminator for these collaborations by comparison with the existing D-Wave implementation is the focus of the former on coherent qubits. In the QAFS programme in the US, for example, use of the aluminium capacitively-shunted flux qubits developed at MIT Lincoln Lab has enabled coherence lifetimes which are both more than three orders of magnitude longer than the niobium qubits currently used by D-Wave and which exceed the typical anneal durations of around 1 microsecond. Fully coherent annealing may offer a number of benefits, most notable being the ability to transition through the minimum gap which acts as a bottleneck for computational speedup in hard (i.e. small gap) problems. Fully coherent annealing is also closer in spirit to closed-system adiabatic quantum computation (AQC) for which there is a proven equivalence to GBQC (and therefore provable quantum speedup).

The International Network in Quantum Annealing (INQA) will for the first time establish a mechanism by which four global collaborations come together to share technical and intellectual know-how and critically analyse developments in theoretical and experimental research in quantum annealing. The network will be led by Prof. Paul Warburton of UCL, who is a co-investigator in the UK's Quantum Computation and Simulation (QCS) Hub and in the recently-announced QEVEC project. He was also previously a co-investigator in the US-led QEO and QAFS collaborations. Other UK researchers who are named network participants in INQA are Prof. Martin Weides of the University of Glasgow (QCS Hub and EU-AVAQUS), Prof. Viv Kendon of Strathclyde University (QCS Hub and QEVEC), Dr Nick Chancellor of Durham University (QCS Hub and QEVEC) and Prof. Andrew Green of UCL. The network will host weekly on-line technical seminars, offer funding to enable international exchange visits between collaborating universities, and run annual conferences. These conferences will be interlaced with the existing annual AQC conferences (which will be part-sponsored by INQA) so as to provide two annealing-specific scientific meetings per year.