What is a quantum computer?

To understand what a quantum computer is and how it works, it is useful to step back and focus on a comparison with classical computers and the notion of information.

A classical computer works by manipulating ‘bits’, which are streams of electrical or optical impulses that represent only two states, current or no current, 1 or 0. This is known as binary logic.

The magic of computing happens because strings of 0s and 1s can represent any type of complex information. These impulses pass through transistors that are assembled into ‘And’ and ‘Or’ logic gates that allow simple operations to occur. Operations such as sum, subtraction, or multiplication. Have enough of them and you can perform any type of calculation.

Quantum computers on the other hand, don’t manipulate electric impulses, but particles themselves, such as electrons or photons. Here is where the magic of quantum physics comes into play and the notion of information shifts.

Particles can exist in two different quantum states at once, a principle called superposition. Relating these states to our previous notion of information, this means that a particle in superposition can represent 0,1 or both the states at the same time. This is called a qubit, the basic unit of quantum information.

While four (4) bits in classical computing can, for example, represent one out of possible sixteen (16) states, four (4) qubits in quantum computing can represent all those 16 states at once. What are the implications of this? And why is that useful?

What does it mean for computation?

The capacity to hold multiple states at the same time means a huge shift from sequential computation to a parallel one. What does that mean in practice?

Imagine a maze. When you ask a classical computer to figure out a way out of it, it will try every single branch in turn, ruling them out until it finds the right path. A quantum computer instead, can go down every path of the maze at once. This means that a quantum computer operating with qubits has an exponential advantage over its classical counterparts.

Through that advantage, quantum computers promise to tackle complex problems and specific tasks that today are hard even for the highest performing classical architecture supercomputers.

It’s important to underline that quantum computers won’t substitute classical computation in its everyday use. Instead, they will be able to bring huge leaps in specific areas of computational problem solving, such as simulations or optimisation of large and complex datasets.

Quantum computers today

Creating and manipulating large numbers of qubits is no easy task. Nowadays quantum computers must be kept at incredibly low temperatures to keep the qubits stable, and various physical problems limiting their scalability are still unresolved.

A race is on between the major companies in the world, IBM, Google, Rigetti, D-Wave, to realise quantum computers with increasingly large numbers of qubits. As of 2021 IBM holds the record with its Eagle processor made of 127 qubits. Experts agree that thousands, if not millions of qubits are needed before quantum computers reach their full potential.

Huge investments and industrial partnerships are already in place to use quantum computers in different areas of research and innovation. Companies such as IBM for example, allow companies to test their quantum computers through specialised software on a quantum cloud.  Volkswagen recently partnered with Google to use its quantum computing capacity in multiple areas: traffic optimisation, self-driving technologies, simulation of new battery architectures and materials.

How can we use quantum computing?

Quantum computers promise to impact many areas of industry and research.

• Chemistry: their vast processing power can be used to simulate digital versions of chemical compounds at an unprecedented scale. Bringing the opportunity to predict new chemical reactions and compounds without the need of a physical lab. This would mean new molecules, drugs, medicines, and materials.
• Financial modelling: prediction of financial market behaviour, deeper analytics, faster trading, improved dynamic arbitrage, portfolio optimisation of large assets.
• Climate change: better weather forecasts, acceleration of discovery of new CO2 catalysts that would ensure efficient carbon dioxide recycling, better battery technologies, vastly improved solar panels, cleaner fertilizers. Real-time Digital Twins modelling natural systems like the weather, the atmosphere, and the oceans.
• Cyber security: new paradigms of encryption that go beyond classical methods of data protection.

Other areas of potential impact are artificial intelligence, with quantum machine learning promising to revolutionise current classical algorithms. The prospect of having a quantum internet that would change the way we securely communicate online. Scientists even hope quantum simulations could help find a cure for cancer.

Despite the field being yet in its infancy, businesses investing now could find themselves having an exponential advantage over competitors once quantum computing starts to deliver its promise. It’s fundamental to act in a timely way, especially in information technology and software systems. The development of new quantum algorithms for example, is an exciting area in which businesses could build know-how today to gain an edge in the future.

Quantum research at Imperial College London

Imperial College London’s Centre for Quantum Engineering, Science and Technology (QuEST) leads research on quantum information and computing in various areas, from quantum chemistry to quantum simulations for materials and cryptography.

Startups from Imperial’s community are also working on the challenge, led by some of top physicists. Orca Computing, co-founded by Imperial’s Provost Professor Ian Walmsley recently confirmed they had been able to create one of the world’s smallest quantum computers, while Professor Terry Rudolph is the co-founder of PsiQuantum, which recently raised $450m in finance to value the company at over $3 billion.

Want to know more?

Are you interested in this future development and what it means to you and your organisation?

Check-out “Quantum“, one of our recently released scenarios for 2041 in collaboration with Imperial College London academics.

Imperial Tech Foresight is foresight backed with the scientific community of Imperial College London. Get in touch to learn more about the possibilities, challenges, and opportunities ahead with such emerging technologies.