Artist's impression of a trapped ion quantum computer

New research by University of Sussex spin-out company, Universal Quantum has determined the parameters needed for a quantum computer to break the encryption of Bitcoin and simulate a crucial molecule in the fight against global food shortages and climate change. These include how big these quantum computers will need to be as well as how long it will take them to solve some of the world’s most pressing challenges, as well as posing a cyber security risk.

Quantum advantage is a major milestone within the quantum computing community. Once achieved, it shows an industrially relevant computational problem solved in a reasonable timeframe that would be practically impossible to do using any classical supercomputer. The two use cases tested by Universal Quantum – breaking Bitcoin encryption and the simulation of FeMoco, the molecule responsible for biological nitrogen fixation – are examples of quantum advantage. The Sussex-based scientists now believe that quantum advantage could be reached in as little as 10 years.

The research findings from Universal Quantum, University of Sussex and quantum algorithm and software developers Qu&Co were published today (Tuesday 25 January 2022) in an Editor's Choice paper in AVS Quantum Science. For the research, the scientists created a tool that automates the calculation of how big a quantum computer needs to be to solve important problems as a function of how long the algorithm is, the desired run time, and key hardware specifications like qubit quality – the basic unit of information used in quantum computing – as well as operation rate.

Quantum computers are exponentially more powerful at breaking many encryption techniques than classical computers. While today's largest supercomputer could never pose a serious threat, current encryption methods will one day be vulnerable to a quantum computing attack. That includes Bitcoin’s encryption and more widespread techniques such as RSA encryption.

Utilising the tool they developed, the scientific researchers found that a quantum computer with 13 million physical qubits could break Bitcoin encryption within a day; and it would take a 300 million qubit computer to break it within an hour.

Mark Webber, quantum architect at Universal Quantum and the paper’s lead author, who embarked on the research whilst studying for a PhD at the University of Sussex, explains: “State-of-the-art quantum computers today only have 50-100 qubits. Our estimated requirement of 13-300 million physical qubits suggests Bitcoin should be considered safe from a quantum attack for now, but quantum computing technologies are scaling quickly with regular breakthroughs affecting such estimates and making them a very possible scenario within the next 10 years.”

The scientists also demonstrated a considerable reduction in the physical size of quantum computers. In 2018, University of Sussex and Universal Quantum physicists determined that the required size of a

trapped ion quantum computer would be in the region of 100m2 – roughly the size of a football pitch – to break RSA encryption. They now estimate that it would need to be just 2.5m2.

When looking at use cases, the researchers made another surprising discovery. One would assume that the speed in which a quantum computer carries out individual operations, the clock speed, solely determines the time a quantum computer requires to solve a particular problem. However, the researchers found that increasing the number of qubits inside the quantum computer can actually compensate for a slower clock speed. This discovery may play an important role helping to decide what is the most suitable hardware platform to build quantum computers capable to tackle important practical applications.

Tackling world food shortages and saving energy

The simulation of the FeMoco molecule, which helps to convert nitrogen in the air into ammonia and is therefore important in the production of fertilizers, is an important test case as it has the potential to use quantum computing to tackle world food shortages and in saving energy – which is why it is a common object of research in quantum computing.

Dr Webber explains further: “We are currently spending around 2% of the world energy supply on just this process, so a better understanding of the FeMoco molecule could greatly improve efficiency in this field with immense positive impact on world food scarcity and the climate crisis. But these two use cases are the tip of the iceberg, we’re only just starting to understand the impact on society for reaching quantum advantage.”

Working with research partners at the University of Sussex and from wider industry, Universal Quantum is building a trapped ion quantum computer at their Haywards Heath Head Quarters. In 2017, Co-founder and Chief Scientist at Universal Quantum and Professor of Quantum Technologies at the University of Sussex, Professor Winfried Hensinger led a global group of scientists in publishing the world’s first blueprint for how to build a large-scale trapped ion quantum computer.

Professor Hensinger explains some of the real-world applications driving their research: “Simulating molecules has applications for energy efficiency, batteries, improved catalysts, new materials, and the development of new medicines. Further applications exist across the board—including for finance, big data analysis, fluid flow for airplane designs and logistical optimisations.”

“One of our focuses at Universal Quantum and in the University of Sussex Ion Quantum Technology group has been on how we can reduce the required size and processing timeframes of a quantum computer to that which is practical for real-world use, whilst having a processing power that is capable of solving some of the most pressing global issues.”

“It’s enormously encouraging to see that in these important test cases we’ve reduced the estimated number of physical qubits that a quantum computer would need to be for quantum advantage, and therefore the size from that of the size of a football pitch to mere meters.” 

The research paper, titled 'The impact of hardware specifications on reaching quantum advantage in the fault tolerant regime' is published in AVS Quantum Science from the American Institute of Physics. The full paper can be found here. Universal Quantum collaborated with the Sussex Ion Quantum Technology Group, part of the Sussex Centre for Quantum Technologies on the research.