Aravind Vijayaraghavan is a British Science Association Media Fellow, funded by University of Manchester


As part of the British Science Festival, Professor Winifred Hensinger from the University of Sussex opened up his laboratory to give a rare glimpse into the inner workings of the most technologically advanced computer in the world.

In the Hitchhiker’s Guide to the Galaxy, Douglas Adams writes of Earth as a gigantic computer built by pan-dimensional beings to run a programme for billions of years, to calculate the answer to the ultimate question of life, the universe and everything. Today, the world is still full of mathematical problems requiring a computer that big, and a programme that long. One such problem is the prime-factorisation of very large numbers. This is no esoteric problem; it forms the basis for the encryption used in banking and cyber-security. Professor Hensinger believes that this, and other very difficult problems, can be solved in a matter of weeks, using a computer that is only the size of a football pitch!

The principle component of a quantum computer is a ‘quantum bit’, or ‘qubit’, which encodes information. In traditional computers, each ‘bit’ can only hold one unit of information – a value of 0 or 1. A qubit on the other hand, can take the value of 1, 0, and anything in-between, and thus can store 4 units of information.

There is another advantage to quantum computers. Everything in the world around us, ultimately, runs on the principles of quantum mechanics, so solving complex problems in quantum mechanics will be best done by a computer which runs using the same principles. A conventional computer can only solve approximations of quantum mechanical problems, requiring first, to convert them into problems of a non-quantum nature, making this approach both tedious and imprecise.

Quantum mechanics involves some strange phenomena, such as entanglement. When two particles are entangled, they can be separated by a large physical distance and have no direct communication, and yet, what happens to one particle will also instantaneously happen to its entangled partner. This can be used to transmit quantum information across vast distances, a process called quantum teleportation. The combination of information storage and manipulation in a qubit, and the transmission of information through quantum teleportation, is what makes a quantum computer tick. Most current theories and explanations of quantum mechanics require additional dimensions, beyond the 3 space and 1 time dimension we are familiar with. So it’s not an exaggeration to say that a quantum computer would do its computation outside the confines of our known universe!

Quantum computers have another, more important, advantage. Everything in the world around us, ultimately, runs on the principles of quantum mechanics. Solving complex problems in quantum mechanics will be best done by a computer which runs on the same principles. A conventional computer can only solve approximations of quantum mechanical problems, requiring first, to convert them into problems of a non-quantum nature, making this approach both extremely tedious and highly imprecise.

So far, most scientists have been developing computers using superconductors to build qubits. The electrons in a superconductor exhibit quantum mechanical behaviours, but only when cooled to within one degree of the coldest possible temperature of 0 Kelvin or -273 Celsius, which is actually colder than the deepest darkest spaces of our universe! This would make a superconducting quantum computer extremely expensive to build and run. 

However, in some modern systems, ionised atoms, where one electron has been removed to make them positively charged, have been employed as qubits. By applying an electric field to an electrode on a chip, the charged ions are made to levitate over the surface. Changing the electric field can make the ion move along the electrode, carrying it from one location to another, to perform computations. Such a system would require no cooling, and could operate at room temperature. Until recently, switching the quantum state of an ion qubit had to be accomplished by shining two very focussed and well directed laser beams on the ion. One can imagine how large, complicated and expensive an ion quantum computer with a billion qubits, 2 billion lasers and many billions of mirrors and lenses can get.

Last year, Professor Hensinger pioneered the use of microwaves to change the quantum state of ion qubits. In a flash, he managed to replace thousands of laser beams with a microwave horn no bigger than a shoebox. Next, he proposed a way to build one large quantum computer with billions of qubits.  It will involve charged ions moving back and forth across many smaller quantum computer units, each mounted on a stage which can be moved with microscopic precision using piezoelectric actuators. A prototype of this mechanism is currently being built and is expected to be completed in two years’ time. Additionally, in partnership with Google and other large technology firms, Professor Hensinger, has published a blueprint, to be constructed at the University of Sussex. He anticipates that this mammoth effort will take 10 to 15 years, and hundreds of billions of pounds.

Which raises the question, will it be worth it?

In the 1940s, at the infancy of traditional computers, there were about 5 computers in the world, and 50 programmers. Each computer required a rather large room to house it in. The first commercial computer produced in the United States, the UNIVAC 1, cost $1.5 million in 1951, which today, would be the equivalent of $50 million. The parallels between the state of conventional computers 60 years ago, and quantum computers today, is rather obvious. In hindsight, it is a no-brainer that every penny spent in developing the computer over the last century has been money well spent.

The next question that arises is – when could we have a quantum computer that is actually useful, that could undertake computational tasks of value, rather than just to demonstrate the working principle? Once again, it would be worthwhile drawing comparisons to the developments in conventional computers. Even the rudimentary electromechanical computer, the Bombe, built in 1939 by Alan Turin, was used to decide the Enigma machine and win the war. Despite the high cost, UNIVAC 1 sold 46 units, and was used by everyone from the U.S. Census Bureau to General Electric.

Currently, there are about 5 quantum computers in the world, which are designed and built to perform very specific types of tasks. But, these are not ‘universal’ quantum computers, which can be programmed like a traditional computer to perform virtually any task as dictated by the programme. Professor Hensinger’s fully programmable universal quantum computer could, in the next decade or two, render the RSA encryption and the fundamentals of banking and cyber security, completely useless. A new highly sophisticated type of encryption, based on quantum mechanical principles, is already being developed, to be deployed with the help of quantum computers. This is the emerging field of quantum cryptography. Such a programmable quantum computer could also speed up other computationally intensive tasks such as the discovery of new pharmaceuticals. We could end up with a deeper understanding of the nature of our universe and perhaps check whether indeed, the answer is 42.