Quantum computing

Citation

Rudall, B.H. (1998), "Quantum computing", Kybernetes, Vol. 27 No. 4. https://doi.org/10.1108/k.1998.06727daa.002

Quantum computing

Quantum computing

Development of quantum computers

New devices based on new technologies are forever being publicised as the basis for new and revolutionary computers. Many sink without trace as the potential manufacturers discover new problems in harnessing new materials in designs that so often still follow the original von Neumann concepts of architecture. In this respect quantum computers are no exception since we have been promised new computing devices based on quantum physics for some time. Different research teams have forecast different computing machines, all, however have been billed as "revolutionary". It is accepted that if a quantum transistor could be produced in quantities for use in computing machines it would inevitably mean computers would run at speeds hundreds of times faster than current models. Most readers will be familiar with what the quantum theoretical studies mean. Electrons that are travelling fast enough can pass through what are considered to be impenetrable structures by quantising. That is, changing their physical state which will allow them to "burrow" or "tunnel" their way through an object.

Research teams worldwide, have been attempting to build quantum transistors which will harness these properties. Many of the results of these projects have been reported in this section. Hopes have been raised in the past and we are now sceptical about claims, particularly those that contain the work "breakthrough" but the goal of increasing the processor speed of computing machines to the extent promised is one that will not be achieved easily.

Quantum transistors

A recent report from scientists working on quantum transistors has been received and it makes very encouraging reading. For several years researchers at the Sandia National Laboratories, Albuquerque, New Mexico, USA, have been working on the development of a transistor that is based on the quantum theory. They have called it Deltt, which they say represents Double Electron Layer Tunnelling Transistor. The leader of the laboratory's development team, Dr Jerry Simmons, is reported as saying that:

Quantum theory is rather like switching on a light bulb without closing a switch. In the quantum transistor, electrons are travelling so fast they are able to "tunnel" their way through a barrier that, under conventional physics, they could not pass through.

What this means is that unlike the ordinary transistor where the electrons are controlled by an electronic switch, in the quantum transistor they are enclosed permanently by gates. It is only when all these electrons have the same amount of energy and are moving at high speed are they able to pass through the enclosing gates. Thus they switch the transistor on and because of the electrons very high speeds the switching occurs much more quickly than in our conventional transistors. When completely proven these new transistors would form part of computer chips which are, of course, the building blocks of our computing machines. The design of any new chips that would include Deltt would have to be new in concept. In fact in any new quantum computer the chips would form an important part of what is likely to be a complex and unproven machine.

Progress in developing the Deltt transistor

Currently the team at Sandia National Laboratories is concerned about the speed of the new transistor. The team leader says that:

We think this could increase the speed of computers by at least ten times, but that is a conservative estimate. The main problem with speed predictions is that we do not have any measuring equipment fast enough. We have been working right on the limit of what our current equipment can measure, so we are really waiting for some new hardware before making accurate predictions.

As to the future viability and timescale Dr Simmonds says that:

Deltt is almost ready for mass production, but we are still at least ten years away from the first quantum computer.

Benefits of mass production of quantum transistors

Some of the consequences of producing such transistors as Deltt would be that:

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  PC prices would fall because quantum transistors are simpler in design and cheaper to make. Also fewer transistors would be needed in a system;

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  power consumption would be less than with current chips ­ making them attractive for use in portable machines;

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  they would probably be used initially in the military in high-speed satellite communication systems and in imaging equipment for spy satellites.

One report of interest to quantum transistor researchers is that the team found that they could turn the transistors on and off using particular light frequencies, and that these frequencies could be easily changed. Another important consideration is that the transistors currently only work at temperatures below ­200°C. The team believe, however, that the ultimate devices will operate at room temperature. At present they are attempting to perfect its manufacturing process. The team hopes to begin licensing discussions with potential manufacturers in the coming year. Even with the production of Deltt we are at least ten years away from the first quantum computer based on it. This would take it well into the next century but, of course, many other teams are working on similar quantum devices and indeed, "genuine breakthroughs" are possible.

Workshop on quantum computing

In September 1997 a workshop was hosted in the UK by Southampton University's Department of Electronics and Computer Science on the "Future of Computing". The workshop explored quantum computing and attracted a number of eminent speakers from the USA and Europe. It was interesting to note that the delegates came from a variety of disciplines. Some were already working on quantum computing and others were considering it. Some, it was reported, attended just to find out what it was all about.

The topic generated a lively debate over the two days and although it was considered to be highly speculative it was accepted that it is obviously an area of increasing interest.

Some of the international speakers who provided insights into the future of quantum computing at the workshop were: Professor Ed. Fredkin (Massachusetts, USA); Professor Leo Stodolsky (Max Plank Institute, Munich, Germany); Professor Tony Hey (Southampton University, UK); Dr Richard Hughes (Los Alamos National Laboratory, USA); Dr Charles Bennett (IBM T.J. Watson Research Centre, USA); Vlatko Vedral (Imperial College, London, UK).

Readers who wish to obtain copies of the presentations and a video of the event should contact: Mark Papiani (Southampton University, UK). Tel: 01703 594788; E-mail: mp@ecs.soton.ac.uk