Prosperity Partnership in Quantum Software for Modeling and Simulation

Nature, at it deepest level, is notoriously difficult to model, as quantum mechanical effects cause the size of the problems to grow exponentially. This poses major challenges in the accurate simulation of molecules and crystals, thus limiting the power of computers to drive major advances in the development of new materials (from batteries and solar cells to superconductors), new chemical processes (designing better catalysts) and new drugs (engineering molecules for desired biological and pharmacological effects). Each of these challenges can be addressed through tools we will help establish in this Prosperity Partnership.

As Feyman observed, the best (and indeed only) way to accurately compute the behaviour of such quantum mechanical systems is to build a computer whose inner workings are fundamentally based on those same quantum mechanical principles. Such so-called 'quantum computers' require radically new hardware able to represent and maintain information in exotic quantum states involving superposition (where quantum bits can be 0 and 1) and entanglement. Major advances are being made world-wide using a variety of hardware platforms, and amongst the leading quantum processors today are those being developed at Google, based on superconducting circuits. In 2018, Google expects to announce a processor with 49 high-quality quantum bits - although this number may seem small compared to the billions of transistors in conventional processor chips, this 49-qubit processor will, we expect, demonstrate the ability to solve a computational problem beyond the capabilities of our most capable supercomputers. This first demonstration of quantum 'advantage' using a quantum processor chip, opens the door for a new research approach looking to characterise and harness the the capabilities of this new hardware and develop applications in the simulation and modeling of materials and molecules.

The Partnership brings together the University of Bristol and UCL and their research groups with long-standing expertise in the theory of quantum computing and simulation, and Google, a world leader in the design and development of advanced quantum computing hardware based on superconducting qubits. Our goal is to develop new and improved algorithms, verification techniques and benchmarks for simulation of quantum systems on near-term quantum computers, which we will implement and demonstrate on Google's hardware. Such an industrial-academic collaboration would have been impossible a few years ago; now working together in this way is essential to efficiently address the main challenges in this area, as our ability to able to run and test problems on real quantum hardware will have a dramatic effect on the pace of quantum application development. In addition, the Partnership includes two UK startups developing quantum software and "quantum-inspired" software sphere, playing a strong role in the development of commercial applications of the results of this project. Through the Partnership, we will therefore build the foundation of a quantum software industry in the UK, with a specific focus on quantum simulation.

Our programme is organised around a set of four main Challenges:

- How can we optimise quantum simulation algorithms for imperfect quantum computers?
- How do we test the behaviour of a quantum machine if it is classically un-simulatable?
- What are the potential applications of quantum simulations in the medium term?
- Can we quantify the computational complexity of problems and use this to improve algorithms?

Each of these raises issues that are both fundamental and practical: the former involving the development of tools that can reframe these questions in a quantifiable way and the latter in in the formulation of explicit practical tests that can be implemented on current devices. In addressing these questions, we aim to develop a firm basis for the development of quantum software well-adapted to current architectures

Economic Impacts
Quantum simulators and pre-error corrected quantum processors are instruments for discovery that can be expected to lead to disruptive advances in a range of sectors. They have the strong potential to lead to innovative products in the *chemical, automotive, and pharmaceutical* industries via the simulation and modelling of nanoscale dynamics and molecules far beyond the reach of today's most advanced tools which cannot, for example, accurately simulate the behaviour of the rechargeable lead-acid traction batteries used in electrical vehicles. Our partnership will help establish a *UK ecosystem in quantum software*, with new businesses focused on quantum application development, working with quantum hardware developers and end-users.

Scientific and Technical Impacts
Our Partnership addresses four key challenges in the development of quantum software for simulation and modeling on near-term quantum hardware, each delivering important impacts:

- A toolset for optimising quantum simulation algorithms for imperfect quantum computers
- A toolset for characterising quantum processors that are classically unsimulatable
- A detailed landscape of near-to-medium term quantum simulation applications, with resource requirements
- An quantitative understanding of the computational complexity of quantum simulation and modeling problems, leading to improved algorithms

To maximise the dissemination of impact in these areas, all our papers will be posted on completion to the arXiv.org open-access pre-print server. Through the development of optimised quantum algorithms for quantum simulation, our research will lead to profoundly new *scientific tools* for industry and academia in the modeling of molecules and materials.

Societal Impacts
The anticipated impacts of practical quantum software applications span a number of societal areas, including *health and wellbeing* (through quantum software for quantum chemistry, a problem at the core of novel drug design), and *connectivity* (through quantum software for data analysis and machine learning, inspired from our understanding of the computational capabilities of early-stage quantum hardware). An improved awareness of the capabilities of near-term quantum computers is likely also to simulate adoption of post-quantum cryptographic methods, leading to improvements in data *security*. Quantum computing continues to grow in prominence in the public imagination and our goal of developing software able to show *useful* advances over classical computing in simulation and modeling using *near-term* quantum processors will play a significant role in the *public discourse* around the actual potential of quantum computers. Our Partnership members (from both academia and industry) have a strong track records in public engagement through lectures, videos and events, which will help maximise this impact, and we will be strongly supported by the Responsible Research and Innovation and Public Engagement teams at UCL and Bristol.

Skills and Training Impacts
Our Partnership brings together dynamic teams from two UK universities, a high-profile international company Google, recent start-ups PhaseWorks and GTN, as well the National Physical Laboratory, offering a unique combination of expertise in quantum information science and breadth of academic, corporate and entrepreneurial environments. Together, these provide a highly attractive and fertile framework for the training of researchers at the Masters, PhD and post-PhD level, helping to establish a skilled *people pipeline* for the UK's emerging quantum software industry. This impact is further supported by close connection with two of the UK's Centres for Doctoral Training in Quantum Technology at UCL and Bristol.