Skip to main content

Reset your password

Please enter the e-mail address you used to register to reset your password

Note: The verification e-mail to change your password should arrive immediately. However, in some cases it takes longer. Don't forget to check your spam folder.

If you haven't received the e-mail in 24 hours, please contact customerservices@ioppublishing.org

Registration complete

Thank you for registering with Physics World
If you'd like to change your details at any time, please visit My account

Close
Home » Page 1962

Quantum information

In the mid-1930s two influential but seemingly unrelated papers were published. In 1935 Einstein, Podolsky and Rosen proposed the famous EPR paradox that has come to symbolize the mysteries of quantum mechanics. Two years later, Alan Turing introduced the universal Turing machine in an enigmatically titled paper, On computable numbers, and laid the foundations of the computer industry – one of the biggest industries in the world today.

Although quantum physics is essential to understand the operation of transistors and other solid-state devices in computers, computation itself has remained a resolutely classical process. Indeed it seems only natural that computation and quantum theory should be kept as far apart as possible – surely the uncertainty associated with quantum theory is anathema to the reliability expected from computers?

Wrong. In 1985 David Deutsch introduced the universal quantum computer and showed that quantum theory can actually allow computers to do more rather than less. The ability of particles to be in a superposition of more than one quantum state naturally introduces a form of parallelism that can, in principle, perform some traditional computing tasks faster than is possible with classical computers. Moreover, quantum computers are capable of other tasks that are not conceivable with their classical counterparts. Similar breakthroughs in cryptography and communication followed.

This quantum information revolution is described in this special issue by some of the physicists working at the forefront of the field. Starting with the most fundamental of quantum properties – single-particle quantum interference in two-path experiments – they show how theorists and experimentalists are tackling problems that go to the very foundations of quantum theory and, at the same time, offer the promise of far-reaching applications.

Anton Zeilinger of the University of Innsbruck introduces the fundamentals of quantum information – quantum bits, entangled states, Bell-state measurements and so forth – and outlines what is possible with quantum communication. The most ambitious scheme, quantum teleportation, has recently been demonstrated with photons and looks to be possible with atoms. The first application of teleportation is, however, likely to be in a quantum computer or communication system rather than anything more cinematic.

Cryptography is the most mature area of quantum information and has now been demonstrated over distances of ten of kilometres (and under Lake Geneva!). Once just the concern of special agents and generals, cryptography now plays an important role in transactions over the Internet. On page 41 of the March issue of Physics World Wolfgang Tittel, Grégoire Ribordy and Nicolas Gisin of the University of Geneva explain how the very properties of quantum theory that so puzzled Einstein et al . can be used to send messages with complete security. A common theme in communication and cryptography is that many applications work best when classical and quantum methods are used in tandem – which is why Alice and Bob, the two central characters in quantum information, are using the telephone in the illustration.

Quantum computers are a more distant proposition, but the first logic gates have been demonstrated in the laboratory and progress is being made on three fronts: trapped ions, photons in cavities and nuclear magnetic resonance experiments. Recent years have also seen significant progress in the development of new algorithms for quantum computers. David Deutsch and Artur Ekert of the University of Oxford present a progress report on page 47 and also delve into some of the deeper implications of quantum theories of information.

Of course it isn’t all plain sailing. Quantum states are notoriously delicate and interactions with the environment can cause a pure quantum state to evolve into a mixture of states. This causes the quantum bit to lose two of its key properties: interference and entanglement. This process, known as decoherence, is the biggest obstacle to quantum computation, as David DiVincenzo IBM and Barbara Terhal of the University of Amsterdam explain on page 53. However, theorists have developed schemes to correct the errors introduced by decoherence and also any inaccuracies generated by the quantum logic gates themselves.

Collaboration is a hallmark of the ever-growing quantum information community. The European Union, for example, is funding a network of eight groups working on the Physics of Quantum Information, while the Quantum Information and Computation collaboration in the US has been awarded some $5 million over five years by the Department of Defense.

We live in an information age that was founded on the applications of basic physics and in which computer power continues to grow exponentially as the feature sizes in microelectronic circuits become ever smaller. Quantum effects can be seen as a threat or an opportunity to this growth. The quantum information technologies described in this issue may have a very long way to go before they rival the sophistication found in their classical counterparts but, as Deutsch and Ekert conclude, “there is potential here for truly revolutionary innovation”.

China plans massive nuclear programme

China is one of the fastest growing nuclear energy markets in the world. Only one per cent of China’s energy needs presently comes from nuclear power and over the next fifteen years China will spend $60 billion on nuclear reactors.

To keep costs down China is pushing hard for foreign investment in its nuclear programmme, and recently it surprised the world’s nuclear industry by signing a series of international agreements. In a $3 billion deal, Russia will supply two 1, 000 MW nuclear reactors to Lianyungang in the eastern Jiangsu province. Canada and France have also agreed to provide financing and technology. Additionally, Atomic Energy of Canada Limited (AECL) has signed contracts to build two 700 MW CANDU reactors at Quinshan.

All the major nuclear power companies are keen to increase sales to China and have offices based in Beijing. And at the end of last year, after years of refusing to do so, President Clinton authorised the sale of US nuclear reactors to China. Presently China’s fledging nuclear industry plans to bring two nuclear reactors on-line every year from 2004.

Discordant policy

Debate has raged in China about how best to proceed with their expansion programme. Until recently, the Chinese government had promoted a two-track approach to its nuclear programme. One part of this policy relies on importing international reactor designs from Europe, Russia, Canada and, shortly, the US. The other approach is for China to develop its own indigenous reactors.

This viewpoint has started to change. Last year in the China Daily, Huangpu Min, director of the Beijing Institute of Nuclear Engineering, argued that China should design its own nuclear power stations. The China Daily newspaper usually indicates ‘official’government policy, and the article has worried overseas firms hoping to sell reactors to China.

All the contracts signed so far contain significant amounts of external financing, hence their attraction to China. Soon the country will standardise on one type of reactor design. When this happens, the company with the winning contract could have an order book of over $60 billion.

China’s Reactors

China was a relatively late-comer to nuclear power. Its first reactor, a Chinese built 300 MW reactor at Qinshan, only went online in 1991. Two years later two French designed reactors, providing power to Hong Kong, went operational at Daya Bay. Presently China is building another three power plants – a French design at Ling’ao, and two CANDU-6 reactors at Qinshan – to come online before the year 2000. These plants will bring capacity up to 6900 MW.

The majority of reactors on order are pressurised water reactors (PWR) in the 600 – 700 MW range similar to those already in operation. China has agreements with all international companies to use as much local material as possible. This is partly to reduce costs to the government, and partly to help build up China’s expertise in reactor production.

For example, China is not yet self-sufficient in nuclear power station technicians and engineers, and the French designed Daya Bay power station still has a number of foreign nationals working at the plant. When the reactor first went operational in 1993, over forty French experts worked at the facility. Now, five years later, after an intensive training programme of Chinese technicians in the UK and France, the number of foreign workers at the plant has been reduced to six and these experts will be replaced soon.

China’s future energy strategy is not just dependent on PWRs, or on domestic requirements. According to a speech by Li Dingfan, vice president of the China National Nuclear Corporation, China is trying to develop a nuclear fuel cycle based on reprocessing. It is also investing heavily in designing an international-level fuel assembly plant. Such a facility would help produce fuel rods for the variety of reactor designs China is currently using. Industry watchers suggest China may market these facilities to international customers. British Nuclear Fuels Limited (BNFL), and its French competitors, are trying to gain contracts related to this design work.

China is also planning to build a large scale commercial reprocessing plant by 2020, and a pilot mixed oxide (MOX) fuel facility in the near future. Construction of a pilot reprocessing plant is already underway in the Lanzhou Nuclear Fuel Complex, along with a spent fuel storage facility. A low- and medium-level disposal plant in the Guangdong province should go operational later this year.

There are many benefits to China developing a large strategic nuclear power programme as the country has extensive natural uranium reserves. Even with massive industrial expansion, it should have enough resources to cater for domestic demand, with an additional surplus available for export.

The Chinese energy market will be the most important source of nuclear contracts over the next thirty years. However, it is unlikely that the international power companies presently competing for contracts, are going to make large profits. It is more likely that China will promote one of its own reactor designs in the near future. The only way for international firms to receive large government contracts will be to strike a domestic manufacturing deal with China’s power industry, and hope that such a highly publicized deal will allow them to sell other reactors at a higher profit margin. Alternatively, and more likely, China may enter the market with a highly competitively priced reactor design of its own.

EU clashes with US over atmosphere tests

HAARP is a facility to study upper atmospheric and solar terrestrial physics. The programme is paid for by the US Air Force and Navy and has already cost hundreds of million dollars. Opponents of the project believe that the defence department is studying ways of improving communications with the US submarine fleet. The array acts like a powerful radar and transmits high frequency 3600 kW signals into the ionosphere.

Starting 35 miles above the Earth’s surface, the ionosphere contains charged particles which distort and deflect radio signals. These particles are produced by the interaction of solar radiation with the atmosphere. HAARP can pump energy some 70 miles into the ionosphere diameter. Military applications for such phenomena are many – devising radar systems, disrupting communications, and improving US logistics.

When the foreign affairs committee invited North Atlantic Treaty Organisation (NATO) and the US permanent representative to NATO to discuss the HAARP project at a public meeting two weeks ago, both groups refused. The secretary general of NATO said that the organisation had neither a policy on this topic, nor an expert they could send to the committee. Tom Spencer, chairman of the committee chairman, vowed to take the matter further, possibly to the US Congress.

Not all researchers believe that opposition to HAARP is justified. Peter Cargill, a space physicist at Imperial College in London, believes that the physics is interesting in its own right, and points out that there are several other facilities carrying out this type of research. “HAARP is just bigger than the other programmes around the world, ” he says. “However, the military don’t spend that kind of money for pure science.”

Plessey sold to Mitel

Plessey will join Mitel’s semiconductor division to form one of the world’s top ten manufacturers of communication semiconductors. Plessey is the 11th company that GEC has sold since September 1996, as it tries to focus on its core businesses of defence and aerospace, telecommunications and industrial electronics.

Plessey is renowned for its application-specific integrated circuits for the telecoms, media and personal computer markets, and recently developed its own 0.35 µm complementary metal oxide silicon (CMOS) technology. It employs about 2700 staff worldwide and made a pre-tax profit of £7.2 m on a turnover of £216 m in 1996/97. Mitel Telecom is a major supplier of telecoms equipment and components and made a profit of $26 m in fiscal year 1997 on a turnover of $485 m.

Managers of Mitel’s semiconductor division will move to Swindon in the UK for a year to integrate the R&D, manufacturing and sales and marketing efforts of the two firms. Ken Robertson, a regional marketing manager for Mitel, says that it is too early to speculate on job losses, but adds that the possibility can not be dismissed. He says that Mitel’s first task will be turn the Plessey business around.

Retinal TV

The growth of virtual reality has increased demand for more realistic video displays, but existing head-up display helmets are expensive and difficult to use. Gerard de Wit and Joseph Braat at Delft have developed a retinal scanning display (RSD) which uses less power and offers higher resolution than current models.

RSD works by adapting the scan line technique found in every TV set. In your TV, an electron beam moves rapidly across the screen to produce the final image. RSD takes this one step further by treating the retina as the screen, and firing a low powered laser beam directly into the eyeball to generate the image.

De Wit and Braat claim that the technique produces an extremely high quality picture and believe that the process can convince the eye that it is seeing a full three-dimensional colour display.

The Delft group are not the only researchers working on this technique. Microvision, a company based in Seattle, US, were recently awarded contracts from the US military for similar headsets. Other companies – such as Boeing and Ericsson Saab Avionics – are evaluating the technology for use in aircraft.

US prepares to go beyond the Endless Frontier

The committee was set up by Newt Gingrich, speaker of the House of Representatives, to update the famous 1945 report by Vannevar Bush, The Endless Frontier, that has formed the basis of US science policy for the past 50 years. Ehlers is vice-chairman of the House of Representatives science committee.

Remarkably, Gingrich has given the committee carte blanche to write the report. “You give me a set of strategic investments large enough worth doing, and then make it my problem to go out and figure out how to find the money”, he told the committee last year. Ehlers, in turn, is inviting comment from the scientific community and has set up a Web site to collect input. The report should be completed later this year. Ehlers’ committee is not the only body evaluating science policy in the US. The National Science Foundation (NSF) is also conducting its own review.

War of words over waste

The broken promise has led to disagreements between the government and the utilities companies that operate nuclear power plants. Underlying the conflict is the fact that the DOE has charged electricity users literally billions of dollars to cover the costs of building a site for the burial of radioactive waste. More than 40 000 tons of used reactor fuel are currently kept on site at 71 nuclear power plants.

The issue has already spilled over into the law courts. Last year, 36 reactor operators brought a case against the DOE in a federal court, arguing that the department should accept responsibility for the waste. The court ruled that the DOE has an obligation to accept used fuel rods from nuclear plants. Moreover, the court found that the DOE cannot excuse itself from the obligation by arguing that it has nowhere to put the waste.

Since then, the utilities and the DOE have duelled over what to do to solve the problem. The DOE has offered to cover some of the extra costs incurred by having to store waste on site, but that offer has met a chilly reception. “What the utilities want is for the energy department to take their spent fuel, ” says Jay Silberg, a lawyer for the utilities.

The DOE counters by pointing to the complexity of finding permanent storage. “The magnitude and seriousness of this task cannot be underestimated, ” says Lake Barrett of the DOE. “But we believe it would be a mistake to divert our resources and efforts to a temporary ‘fix’ which could undermine our focus on obtaining a permanent solution, ” he adds.

The focus of the DOE’s efforts is a site in Yucca Mountain, Nevada. Scientists and engineers are carrying out a “viability assessment”, due in autumn, of the site’s suitability as a permanent waste repository. If the assessment is favourable, the DOE will prepare an environmental impact statement next year, and work on the site could begin in 2001.

Cheaper fusion machine sought

The international thermonuclear experimental reactor (ITER) was intended to demonstrate the scientific and technological feasibility of fusion energy by producing an ignited, energy-yielding plasma for the first time. Construction was scheduled to start after the engineering design activities were completed in July this year. These activities will now be extended for another three years while the partners seek a cheaper alternative to the present design.

An estimated $1bn has been spent on developing the reactor over the past decade. Nevertheless, the decision to delay construction was widely expected. Partners in the ITER project had also been advised to pursue a cheaper fusion programme by several sources.

The decision to delay ITER will impact on the Joint European Torus (JET) at Culham in the UK. The world’s leading magnetic confinement fusion experiment, JET is intended to prepare the way for ITER. “This decision gives greater importance to data coming from JET” says Alan Gibson, deputy director of JET.

NASA looks to next Mars mission

The Surveyor 98 mission consists of a satellite called Mars Climate Orbiter, and a ground probe, Mars Polar Lander. Both craft will arrive at Mars during 1999. The orbiter will spend two years measuring atmospheric properties – such as volatiles and water vapour – and taking high-resolution photographs of the surface. The lander will search for subsurface water during its three month mission. Its payload includes cameras, a robotic arm and soil composition instruments.

For the first time a public interest organization, the Planetary Society, will provide an instrument, for a NASA probe. The Mars microphone will allow researchers to actually hear sounds from another planet.

The idea of a microphone on Mars was originally proposed by Carl Sagan in the early seventies. He believed that having such an instrument on Mars would heighten public interest in science. Louis Friedman, executive director of the Planetary Society, agreeds “The microphone will add drama and a sense of adventure to the 1999 arrival of the Mars Polar Lander.”

The Planetary Society raised funds from over 2000 private donations for the microphone. The society contracted Janet Luhman of the Berkeley Space Science Laboratory, University of California, to design the microphone. “They have a group there with good hardware experience” says Friedman. The team kept costs low by using off-the-shelf parts. Students and research associates helped design the instrument.

The device is part of an LIDAR (light detection and ranging) instrument package built by the Russian Space Research Institute (IKI). The Russian experiments are designed to examine the presence and altitude of dust and aerosols in the atmosphere. This is first time a Russian instrument will fly aboard a US planetary mission.

Anyone will be able to download sounds from Mars over the Internet if the landing is successful. Students can also add their name to a microchip which will be placed on the lander.

The actual landing site was recently photographed by Mars Global Surveyor and suggests a more dramatic landscape than previous Mars missions. “The 75 degree south latitude landing zone is quite a bit more rugged and geologically diverse than we had previously thought” said Dr. Michael Malin, one of the mission’s principal investigators.

Mars Global Surveyor will narrow down the best landing sites for the lander over the next year.

Newsbytes: Voyager, NASA and Edinburgh

NASA Safety Advisory Panel presents report

The Aerospace Safety Advisory Panel (ASAP) has presented its 1997 report. The panel provides a independent assessment of the safety features in NASA’s space program. The group was set up after the Apollo 1 capsule fire in 1967. This year the panel recommends that NASA keeps a closer watch on the Shuttle contractors, now that launch facilities are operated by a commercial company. They also ask NASA to investigate new long-exposure radiation standards for astronauts based on Mir and the future International Space Station.

The report is available here.

Voyager ‘boldly goes where no probe has gone before’

Last Tuesday Voyager 1 officially became the most distant manmade object from Earth. It now takes nine hours and 36 minutes for a radio signal to reach the spacecraft which is now 6.5 billion miles away. Voyager is collecting data on the Sun’s heliosphere and will soon reach the heliopause – the boundary between the solar system and interstellar space.

PPARC name first director of Astronomy Technical Centre

Adrian Russell has been appointed by PPARC as the first director of the UK Astronomy Technology Centre. The center will design and produce the UK’s new range of telescopes. Russell is currently the UK project manager for the Gemini telescope project.

Copyright © 2026 by IOP Publishing Ltd and individual contributors