A roadmap for the future of quantum simulation

Quantum computers are hugely powerful devices with a capacity for speed and calculation which is well beyond the reach of classical, or binary, computing. Instead of a binary system of zeroes and ones, it operates through superpositions, which may be zeroes, ones or both at the same time.

The continuously-evolving development of quantum computing has reached the point of having an advantage over classical computers for an artificial problem. It could have future applications in a wide range of areas. One promising class of problems involves the simulation of quantum systems, with potential applications such as developing materials for batteries, industrial catalysis and nitrogen fixing.

The paper, published in Nature, explores near- and medium-term possibilities for quantum simulation on analogue and digital platforms to help evaluate the potential of this area. It has been co-written by researchers from Strathclyde, the Max Planck Institute of Quantum Optics, Ludwig Maximilians University in Munich, Munich Center for Quantum Science and Technology, the University of Innsbruck, the Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, and Microsoft Corporation.

Professor Andrew Daley, of Strathclyde's Department of Physics, is lead author of the paper. He said: "There has been a great deal of exciting progress in analogue and digital quantum simulation in recent years, and quantum simulation is one of the most promising fields of quantum information processing. It is already quite mature, both in terms of algorithm development, and in the availability of significantly advanced analogue quantum simulation experiments internationally.

"In computing history, classical analogue and digital computing co-existed for more than half a century, with a gradual transition towards digital computing, and we expect the same thing to happen with the emergence of quantum simulation.

"As a next step along the development of this technology, it is now important to discuss 'practical quantum advantage,' the point at which quantum devices will solve problems of practical interest that are not tractable for traditional supercomputers.

"Many of the most promising short-term applications of quantum computers fall under the umbrella of quantum simulation: modelling the quantum properties of microscopic particles that are directly relevant to understanding modern materials science, high-energy physics and quantum chemistry.

"Quantum simulation should be possible in the future on fault-tolerant digital quantum computers with more flexibility and precision, but it can also already be done today for specific models through special-purpose analogue quantum simulators. This happens in an analogous way to the study of aerodynamics, which can be conducted either in a wind tunnel or through simulations on a digital computer. Where aerodynamics often use a smaller scale model to understand something big, analogue quantum simulators often take a larger scale model to understand something even smaller.

"Analogue quantum simulators are now moving from providing qualitative demonstrations of physical phenomena to providing quantitative solutions for native problems. A particularly exciting way forward in the near term is the development of a range of programmable quantum simulators hybridising digital and analogue techniques. This holds great potential because it combines the best advantages of both sides by making use of the native analogue operations to produce highly entangled states."

The University of Strathclyde and all of the partners on this perspective article have large, active programmes involving both theory of architectures and algorithms, as well as development of platforms for analogue quantum simulation and digital quantum computing. The partners have been collaborating as part of the Horizon 2020 EU Quantum Technologies Flagship project PASQuanS. At Strathclyde, research in this area is strongly embedded in the UK's national quantum technology programme, and has received substantial funding from UK Research and Innovation.

A Quantum Technology Cluster is embedded in the Glasgow City Innovation District, an initiative driven by Strathclyde along with Glasgow City Council, Scottish Enterprise, Entrepreneurial Scotland and Glasgow Chamber of Commerce. It is envisaged as a global place for quantum industrialisation, attracting companies to co-locate, accelerate growth, improve productivity and access world-class research technology and talent at Strathclyde.

The University of Strathclyde is the only academic institution that has been a partner in all four EPSRC-funded Quantum Technology Hubs in both phases of funding. The Hubs are in: Sensing and Timing; Quantum Enhanced Imaging; Quantum Computing and Simulation, and Quantum Communications Technologies.