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Information is power, but these days we have so much of it that our computers are struggling to put it all to good use. To achieve that, we need something superior to existing computers, something with awesome processing abilities; something like a quantum computer.
"It is going to be like the classical computer was in the '70s," predicts Stevano Sanvito, professor of condensed matter theory at TCD, and leader of the computational spintronics group which is working on designing materials best suited to quantum computing.
In the next five to 10 years, quantum computers will revolutionise medicine and industry, he predicts. It will become possible, for example, to find new drugs much more quickly than is possible today, to more accurately predict the weather, say every 10 minutes across a small geographical area, or better predict financial markets.
"Quantum computing will allow us to solve problems that at the moment cannot be tackled because they are too complex or too large for classical computers," Sanvito says. "We will be able to solve problems that require manipulation of enormous amounts of data."
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To understand quantum computers, and how they work, we must first look at classical computers. These use a basic language, which has an “alphabet” of just two numbers; zero and one. These two numbers can be thought of as akin to the “on” and “off” positions on a light switch. The ‘one’ value describes when the electrical flow is on, and zero when it is off.
The more rapidly a classical computer can control its internal flow of electricity and switch between zero and one values, the faster it can work. This control is achieved with transistors, which act as tiny on-off switches that live in the microprocessor, or brain, of the computer.
The more transistors on a chip, the more powerful it is. In the early 1970s, engineers managed to squeeze a few thousand transistors on to a chip. These days there are billions of transistors on our chips and manufacturers are running out of available places to put them. In this sense, classical computers are now living on borrowed time.
The origins of the quantum computer lie in the field of quantum mechanics, which details the weird physics governing how atomic and subatomic particles behave. In the quantum world, tiny particles do not exist in one clearly defined state or another, such as one or zero, but across an infinite number of possible states somewhere in between.
A thought experiment called Schrodinger's cat was devised in 1935 by physicist Erwin Schrodinger to describe quantum systems. In it, he described the field as being like a cat, inside a sealed box containing radioactive poison, that is either dead or alive, until the box is unsealed, when the cat is observed, and seen to be dead.
Schrodinger adeptly describes the lack of certainty that exists in the quantum world, as well as how particles are forced to choose a definite value following interaction with the classical world we live in. Thus, the cat can be either dead or alive until observed to be dead.
"Let's now try to extrapolate this example to see why quantum computers are more efficient than classical ones," explains Dr Alessandro Lunghi of TCD school of physics.
“Let’s pretend for a second that people like us could behave in a quantum fashion,” Lunghi adds. “That would mean that a person could be in multiple places at the same time, doing different things at the same time, so that would be the ultimate multitasking if you want.”
There is an additional, useful property of quantum mechanics, called entanglement, he continues. “That would be that it’s not just me doing multiple things, but at the same time I can talk to you, and we can co-operate and we can do more things altogether.”
Qubits
The basic unit of information in a classical computer is a bit, while in a quantum computer it is called a qubit. Qubits are defined as any tiny particle that behaves according to quantum mechanics. They can be an electron, an atom or a molecule, for example; but, unlike bits, they are not easy to control and this represents a major technical challenge.
The reason qubits are not easily controlled is because when they interact with the environment, the ‘big world’, they change. This interaction – in ways not fully understood – forces the qubit, which up to then has unlimited potential values, to become one definite value.
In practical terms what this means is that qubits – the building blocks of a quantum computer – must be kept isolated from the environment so that they do not lose their unlimited, quantum properties. Building a quantum computer while keeping its qubits isolated is a big challenge, akin to building a house, without interacting with bricks and mortar.
The qubits, for example, can also be destabilised by interacting with vibrational forces produced by the atom, which can also result in the loss of the quantum properties of the particle. Scientists have solved this issue by lowering the temperature of the particles to -273 degrees, but working at such temperatures is costly and technically challenging.
Scientists say that by reducing temperatures to close to absolute zero, atoms can be held in a stable configuration. This eliminates, or almost eliminates the destructive effect of atomic vibrations on the qubit.
There are many research groups, including at TCD, that are looking to identify new materials that can preserve the quantum properties of qubits, without the requirement of working at very low temperatures. The TCD research is being done with the help of computer simulations.
In 1997, the supercomputer announced its superiority over humanity when IBM's Deep Blue, beat Garry Kasparov, the then world chess champion. It was the first time a computer had achieved this feat.
Kasparov was distraught after his defeat, but on October 23rd, 2020, it was the turn of the supercomputer to face a superior foe.
That was the day that Google announced that its quantum computer had achieved "quantum supremacy" over a supercomputer. The Google quantum computer performed a series of operations in 200 seconds which would take a classical supercomputer 10,000 years to complete.
The downside was that the quantum computer used more electricity because it had to operate at super-cold temperatures, but perhaps it’s a small price to pay. “If you think about how much electricity it costs to run a supercomputer for 10,000 years, it is certainly more than this 200 seconds at very low temperature,” Sanvito notes.
Applications
Quantum computers will, researchers in the field say, be able to solve problems that are currently unsolvable. For example, understanding the relationship between a person’s DNA fingerprint and their likelihood of developing particular diseases – or finding new drugs to fight diseases.
It will also become possible to solve those problems that are currently solvable on a classical computer, even a supercomputer, but not easily. In such cases, a quantum computer could produce solutions more quickly and more accurately. An example here might be the weather, where it could become possible to predict weather every 10 minutes over, say, a square kilometre.
The great advantage quantum computers have over classical ones is that they have the ability to cope with enormous amounts of data by running innumerable computations in parallel, or all at once. This is why they are expected to be deployed early on to do database searches.
Ireland does not have the resources to compete with the multinationals or the larger countries, but it does have pockets of quantum expertise, notably at TCD, UCD and the Tyndall National Institute in Cork. There is particular excellence in the relevant areas of software development, the analysis of the coherence issue with qubits, and quantum education.
There is also the advantage of having most of the companies who are working in quantum computing having a significant presence in Ireland, including IBM, Microsoft, Google and Amazon. This opens opportunities for researchers to partner with industry on specific quantum problems.
Quantum activities here are facilitated by the Irish Centre for High End Computing (ICHEC). The centre operates Ireland's national supercomputer, called Kay, and is involved in quantum computing because it sees it as part of high-performance computing here.
ICHEC is involved in the use of so-called digital twins. These are digital models representing the real world, where, for example, the impact of government policies on citizens and the environment can be tested before they are implemented. Quantum computers can improve them.
"You might couple a model that represents a transport system with a model that represents air quality in an area," says Venkatesh Kannan, ICHEC's novel technologies programme manager. "Coupling these kinds of systems across different domains makes the digital twin more complex, but also more powerful."
ICHEC is collaborating with the University of Oxford, he points out, on applying quantum computing to the hard problem of natural language processing. It is, computationally speaking, both complex and expensive for classical computers to try to understand meanings of sentences.
“If you are able to improve the comparison of sentence meanings then it has potential applications in fields like machine translation or detecting the sentiment or intent in a sentence, and even, going forward, conversational AI,” Kannan explains.
The quantum computing ecosystem in Ireland should benefit next year from the rollout of a national quantum learning platform, that will be coupled to the supercomputer Kay. This will be made available to academics and industry for training and testing quantum concepts.