There is still some way to go, however, before the technology moves into the mainstream. “The reality of quantum computing is probably 10 to 15 years away, yet it merits our attention now,” says Dr. Seungyun Lee of the joint technical committee for information technology (JTC 1) established by IEC and ISO.
“The excitement in the industry for this new paradigm of computer hardware is understandable, given the promise of far greater computational power with whole new multidimensional capabilities.”
What is quantum computing?
The computers we have today store data using bits, which have two states — either on or off — represented as a 1 or a 0. Quantum computing replaces these binary bits with qubits that have more states which are changing continuously. Qubits can be on, off or somewhere in between all at the same time. This state is called superposition and enables qubit-based computers to carry out far more calculations much faster. When qubits become entangled they share all the possible combinations of the quantum states of the individual qubits, substantially boosting computational power in the process.
In terms of what is already possible, scientists have combined quantum computing with machine learning for the processing of images and the calculation of probabilities. Shor’s quantum computing algorithm is already having a major influence on the world of cyber security and traditional encryption methods. Elsewhere, quantum simulators are facilitating the study of quantum systems — such as quantum chemistry or quantum field theory — that are difficult to study in the laboratory. These are just three examples.
In order to realize quantum supremacy, though, researchers will need to find ways of increasing the about 20 superconducting qubits in today’s largest quantum computers to at least 50. The challenge is the extreme fragility of quantum systems. Quantum computers are particularly prone to errors because qubits are highly sensitive to external noise. Qubits only function “coherently” when they are enclosed in sealed boxes fitted with vacuum pumps and cooled down to mere thousandths of a degree above absolute zero. This protects them from the destabilizing effects of radiation, light, sound, vibrations and magnetic fields.
Letting the cat out of the box
The good news is that scientists may have found the route to solving the problem of errors in quantum computing. Earlier this year, the researcher at Yale University announced they had found a way to save Schrödinger’s cat. The significance and implications are enormous.
In the famous thought experiment, the Austrian physicist, Erwin Schrödinger, places his imaginary cat in a sealed box, together with a flask of poison and a quantity of radioactive material. A single atom of leaking radiation is enough to shatter the flask and poison the cat. Quantum superposition theory suggests that until someone looks inside the box, the cat is both alive and dead, but the mere act of opening the box immediately changes the cat’s quantum state to either alive or dead. This change, which was believed to be instantaneous and unpredictable, is called a quantum jump, or sometimes leap.
Until now, the assumption was that property changes to subatomic particles happen in an abrupt way, rather than flowing between states. For example, the thinking was that an electron in a low-energy state would snap rather than transition into a higher energy state when more energy was added. When you are not looking, superposition kicks in and it is in both states and somewhere in-between, all at the same time. As soon as you look, it changes into one state or the other, like Schrödinger’s paradox.
The Yale researchers appear to have demonstrated that although quantum jumps are very fast, they are neither abrupt nor random. The implication is that it might be possible to detect and anticipate imminent jumps. Spotting errors before they arise could offer ways of preventing them.
Two flavours of quantum computers
The research offers a promising point of departure but until a solution is found, there will be limitations on the size and complexity of problems that quantum computers are able to tackle. This has led to the development of devices that take a radically different approach to quantum computing.
Classical computers use transistors, known as gates, to control the flow of electricity through a circuit. They are like power switches, on or off, one or zero. In the quantum model, qubits replace the transistors. When someone eventually achieves quantum supremacy, it will be with a gate-based quantum computer.
In the meantime, scientists have developed quantum annealing devices to solve a much narrower range of problems. Unlike quantum gate-based computers, quantum annealers create an environment where only restricted, local connections are possible. The quantum state of the qubits is more fragile and their manipulation is less precise. For the right kind of problem, however, quantum annealers offer a huge increase in processing speed compared to classical computing.
Quantum annealers have already been used to solve optimization problems in the domains of finance and the aerospace industry, among others, with potential users limited only by the upwards of USD 10 million cost of a quantum annealing device. It would be wrong, though, to think of gate-based quantum computers and quantum annealers as competing technologies. They are simply useful for solving different problems.
The power of quantum cryptography
As computers become more powerful, however, and in the face of rogue states with the technology resources to pose a more serious threat, cryptographers are turning away from mathematics and also looking to the laws of quantum mechanics to achieve greater security. As in the related field of quantum computing, it is based on the behaviour of quantum particles, which are smaller units than molecules. For example, an encryption system called quantum key distribution (QKD) encodes messages using the properties of light particles.
The only way for hackers to unlock the key is to measure the particles, but the very act of measuring changes the behaviour of the particles, causing errors that trigger security alerts. In this way, the system makes it impossible for hackers to hide the fact that they have seen the data.
The threat is so great that scientists are urging organizations to start looking at and adopting quantum encryption systems. Quantum computers may not be available for another decade, but quantum cryptography has already been available for a few years.
IEC and ISO have set up a study group in their joint technical committee to identify the standardization needs of quantum computing. After completing an initial study of key concepts and describing the relevant terminology, the international group of experts is studying the requirements of society, markets and technology for future standardization, as well as closely following developments in quantum computing. Quantum cryptography is an area of interest for several IEC expert groups.