Understanding quantum computers
Quantum computing comes in two flavours: annealing and gate-based. Here is how they work.
The American physicists Paul Benioff and Richard Feynman first put forward the concept of quantum computing in the early 1980s. British scientist David Deutsch only described the first universal quantum computer in 1985. That is comparatively recent as technologies go and scientists expect it will be at least another decade before they are ready for the, er, quantum leap into the future. But a lot has been achieved in a relatively short time.
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.
Quantum computers come in two flavours. Gate-based quantum computing more or less works in the same way as traditional computing. A transistor performs a Boolean function: a sort of binary logic, commonly seen in advanced search engines, that works with modifiers such as ‘AND’ or ‘NOT’. The transistor receives two incoming signals and depending on what it encounters, sends out a new electric signal. In the quantum model, qubits replace the transistors.
The main challenge is increasing the small number of qubits possible today to industrial scale, which is difficult because it is a struggle to keep qubits in their quantum state. Qubits only function “coherently” when they are cooled down to mere thousandths of a degree above absolute zero, which also protects them from the destabilizing effects of radiation, light, sound, vibrations and magnetic fields. All of this limits the size and complexity of problems that gate-based quantum computers are currently able to tackle.
Computers based on quantum annealing take a radically different approach. Quantum annealers run adiabatic quantum computing algorithms. Instead of allowing the entanglement of all qubits, they create an environment where only restricted, local connections are possible. When they attain superposition, they can be used to mediate and control longer range coherences. This makes them suitable for a much narrower range of tasks, such as solving optimization problems — i.e. choosing the best solution from all feasible solutions.
Quantum annealers have already been used to solve such problems in the domains of finance and the aerospace industry, among others, with potential users limited only by the upwards of 10 million dollars cost of a quantum annealer device. As with gate-based quantum computing, decoherence is a major challenge for quantum annealers and they too require massive refrigeration units. The limited number of tasks that quantum annealers can perform means, for example, that they are unable to run Shor’s “decryption” algorithm. There will be more about this last point later.
It would be wrong to think of gate-based quantum computers and quantum annealers as competing technologies. They are useful for solving different problems. Quantum annealers are sometimes dismissed as not being proper computers, but unlike gate-based quantum devices, they are already delivering significant results. Both technologies face an array of similar challenges, including the need for a radically new software stack. As discussed, they share a common decoherence problem, as qubits cannot inherently reject noise. Because qubits are susceptible to perturbations, errors are hard to eliminate. And quantum algorithms are very difficult to design.
Quantum computing looks set to bring massive benefits, such as accelerating medical research, making advances in artificial intelligence and perhaps even finding answers to climate change. These can be broken down into three areas. Firstly, scientists have combined quantum computing with machine learning for the processing of images and the calculation of probabilities. Secondly, marrying quantum computers with Shor’s algorithm is having a major impact on the world of cyber security and traditional encryption methods. Lastly, quantum simulators facilitate the study of quantum systems — such as quantum chemistry or quantum field theory — that are difficult to study in the laboratory.
They will have a massive impact on the critical area of cyber security. Quantum computers will be powerful enough to crack the encryption codes that currently protect all our sensitive data, from mobile banking to medical records. That is why scientists are urging governments and organizations to start exploring and implementing quantum encryption systems now.
It is clear that quantum computers will have a disruptive and transformative effect, possibly greater than anything we have ever seen before when combined with technologies like artificial intelligence. We need to start preparing now in order to address the needs of industry and society, as well as to share best practices more efficiently to facilitate innovation. International Standards can play a major role by exchanging best practices and ensuring that the technology works and is safe.
The IEC and ISO have set up a study group in their joint technical committee (JTC1) 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 will study the requirements of society, markets and technology for future standardization, as well as studying current technologies that are being used in quantum computing.
Indian IT consultant Anupam Agrawal is one of the experts participating in the JTC1/SC7 study group. He urges regulators and lawmakers to become involved sooner rather than later: “They should participate in advance in order to understand the nuances of the technology while they carve out related policies. The impact of quantum computing may require many of their policies to be revisited.”
