From the rapid development of new vaccines to the creation of more efficient batteries to store the clean energy of the future, many crucial innovations are slowed by the limits of current computer technology. Quantum computers of the future will have the power to break through the barriers and enable the design of new medicines and materials, to name but two potential life-changing quantum computing applications.
In many fields, computers have revolutionised the innovation cycle. In aerospace, for example, we ‘design’ new aircraft on powerful supercomputers. Contrast this with the Wright brothers who ‘discovered’ motorised flight through protracted cycles of trial and error. How is this possible? Because we have two things: a set of equations based on Newtonian physics that describe how air flows, and, with supercomputers, the computational power to solve them.
Newton’s laws of physics, and the science of classical mechanics that have developed from them, have underpinned three centuries of exponentially accelerating human progress, greater than all prior human progress across history.
But these laws break down when we try to fully understand how nature works on a molecular level. Using even the most high-performance computers in the world today, we simply can’t see and thus simulate how new medicines interact with a candidate protein in the body for example. Or identify new chemical catalysts that can efficiently capture carbon dioxide from the atmosphere for a greener planet. Only the science fiction-like laws of quantum mechanics can help us design our way to solutions such as these. Physicists working at the beginning of the 20th century were keenly aware of the limitations of classical mechanics, and so the leading minds set about developing a new mathematical equation: one that could explain, in the words of Richard Feynmann, ‘nature as She is -- absurd’. The result was quantum mechanics, a perfect model of the world.
In 1929 the British physicist Paul Dirac was so delighted with the theory of quantum mechanics that he wrote: ‘The underlying physical laws necessary for the mathematical theory of a large part of physics and the whole of chemistry are thus completely known’.
So why aren’t we already using quantum mechanics to design new products and transform society? The Dirac equation highlights the interaction of these particles and electrons, and how they interact and move over time. Yet we don’t have the computational power to manipulate these elements to solve these equations directly.
The problem can be neatly summed up by the second half of Dirac’s quote: ‘the difficulty is only that the exact application of these laws leads to equations much too complicated to be soluble’. This challenge is no less intractable with today’s classical computers – almost 100 years later we still lack the computational power to solve the equations of quantum mechanics for almost all systems of practical interest, even if we had all the world’s supercomputers working together.
To break through the limits of classical computing we need a completely different type of computer, one constructed from building blocks that behave according to the principles of quantum mechanics. These machines, quantum computers, will be able to simulate nature in all its complexity on a molecular level because they naturally operate in this quantum space.
Until that past decade, their existence was purely theoretical. Now we’ve proven quantum computers are very real. The next challenge is to prove they can scale to the size and reliability to handle error free data processing at an unfathomably enormous scale. We’re still early on that journey but making steady big leaps.
The implications are mind-blowing. Large-scale quantum computers will progress humanity from an age of discovery to a new age of design, a paradigm shift as significant as the industrial and digital revolutions.
In the pharmaceutical industry, for example, by simulating in exquisite detail how a drug binds a target protein, we will be able to design drugs that we know work with high efficacy and specificity, rapidly accelerating the development of new medicines and saving the billions of dollars which are currently wasted on drugs that fail in clinical trials. The COVID-19 pandemic has been a powerful illustration of how many lives we can save if we can develop drugs and vaccines faster.
By simulating the complex cycle of chemical reactions which occur inside a fuel cell, we will be able to design catalysts that unlock the full potential of hydrogen as a clean energy source and reduce our reliance on rare metals that are expensive and environmentally damaging to extract from the earth.
Our increasing dependence on the digital world intensifies our vulnerability to cyber-terrorism, as conventional random number generators are not truly random and thus open to compromise. These risks create a vast number of challenging processes for classical computers, with the need to establish an extensive security support system to tackle daily threats. Quantum computing has the potential to transform the world of cyber-security by generating truly random numbers to increase cyber-security.
For these transformational applications to be possible, we need quantum computers that are much larger and more reliable than those we have today. It is estimated millions of qubits will be needed to achieve true ‘quantum usefulness’. Today the biggest quantum computers have one to two hundred.
The key for quantum computers to reach functional scalability is to overcome the challenge of the sensitivity of qubits to their environment. We need to be able to correct as many as billions of data errors in milliseconds. To put that into simple numbers, we need a 10,000-fold reduction in system errors to run the most powerful quantum algorithms. Achieving this goal, solving the problem of quantum error correction, is quantum computing’s biggest technical challenge.