'Quantum computer' a stage closer with silicon breakthrough

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london-nano.com/" target="_self">London Centre for Nanotechnology

Nature paper

The remarkable ability of an electron to exist in two places at once has been controlled in the most common electronic material - silicon - for the first time.

The research findings - published in Nature by a UK-Dutch team from UCL, the University of Surrey, Heriot-Watt University in Edinburgh, and the FOM Institute for Plasma Physics near Utrecht - marks a significant step towards the making of an affordable "quantum computer".

According to the research paper in Nature the scientists have created a simple version of Schrodinger's cat - which is paradoxically simultaneously both dead and alive - in the cheap and simple material out of which ordinary computer chips are made.

"This is a real breakthrough for modern electronics and has huge potential for the future," explained Professor Ben Murdin, Photonics Group Leader at the University of Surrey. "Lasers have had an ever increasing impact on technology, especially for the transmission of processed information between computers, and this development illustrates their potential power for processing information inside the computer itself. In our case we used a far-infrared, very short, high intensity pulse from the Dutch FELIX laser to put an electron orbiting within silicon into two states at once - a so-called quantum superposition state. We then demonstrated that the superposition state could be controlled so that the electrons emit a burst of light at a well-defined time after the superposition was created. The burst of light is called a photon echo; and its observation proved we have full control over the quantum state of the atoms."

And the development of a silicon based "quantum computer" may be only just over the horizon. "Quantum computers can solve some problems much more efficiently than conventional computers - and they will be particularly useful for security because they can quickly crack existing codes and create un-crackable codes," Professor Murdin continued. "The next generation of devices must make use of these superpositions to do quantum computations. Crucially our work shows that some of the quantum engineering already demonstrated by atomic physicists in very sophisticated instruments called cold atom traps, can be implemented in the type of silicon chip used in making the much more common transistor."

Professor Gabriel Aeppli, Director of the London Centre for Nanotechnology added that the findings were highly significant to academia and business alike. "Next to iron and ice, silicon is the most important inorganic crystalline solid because of our tremendous ability to control electrical conduction via chemical and electrical means," he explained. "Our work adds control of quantum superpositions to the silicon toolbox."

Image: The electron motion in silicon. The electron orbits a phosphorus atom embedded in the silicon lattice, shown in silver. The undisturbed electron density distribution, calculated from the quantum mechanical equations of motion is shown in yellow. A laser pulse can modify the electron's state so that it has the density distribution shown in green. Our first laser pulse, arriving from the left, puts the electron into a superposition of both states, which we control with a second pulse, also from the left, to give a pulse which we detect, emerging to the right. The characteristics of this 'echo' pulse tell us about the superposition we have made.

Media contact: Dave Weston

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About the London Centre for Nanotechnology:

The London Centre for Nanotechnology is an interdisciplinary joint enterprise between University College London and Imperial College London. In bringing together world-class infrastructure and leading nanotechnology research activities, the Centre has the critical mass to compete with the best facilities world-wide. Research programmes are aligned to three key areas, namely Planet Care, Healthcare and Information Technology and exploit core competencies in the biomedical, physical and engineering sciences. Website:www.london-nano.com

About UCL (University College London)

Founded in 1826, UCL was the first English university established after Oxford and Cambridge, the first to admit students regardless of race, class, religion or gender, and the first to provide systematic teaching of law, architecture and medicine. UCL is the fourth-ranked university in the 2009 THES-QS World University Rankings. UCL alumni include Marie Stopes, Jonathan Dimbleby, Lord Woolf, Alexander Graham Bell, and members of the band Coldplay. UCL currently has over 12,000 undergraduate and 8,000 postgraduate students. Its annual income is over £600 million. www.ucl.ac.uk

About The University of Surrey:

The University of Surrey is one of the UK's leading professional, scientific and technological universities with a world class research profile and a reputation for excellence in teaching and research. Ground-breaking research at the University is bringing direct benefit to all spheres of life - helping industry to maintain its competitive edge and creating improvements in the areas of health, medicine, space science, the environment, communications, defence and social policy. Programmes in science and technology have gained widespread recognition and it also boasts flourishing programmes in dance and music, social sciences, management and languages and law. In addition to the campus on 150 hectares just outside Guildford, Surrey, the University also owns and runs the Surrey Research Park, which provides facilities for 140 companies employing 2,700 staff. The Sunday Times names Surrey as 'The University for Jobs' which underlines the university's growing reputation for providing high quality, relevant degrees. Web site www.surrey.ac.uk

About Heriot-Watt University:

Heriot-Watt is recognised internationally as a centre for high calibre research in science, engineering and business. We've been rated as a leading research institution by the RAE, the national review body, and are now in the top 35 universities in the UK for our research. We have an unsurpassed international in-country presence, delivering degree programmes to 11,800 students in 150 countries around the world. We do this via distance learning programmes and our innovative Approved Learning Partner network which comprises 50 institutions in 30 countries. We also have the largest international student cohort in Scotland with about one third of our students coming from countries outside the UK. Heriot-Watt now provides more graduates per year across the physical sciences, mathematics, engineering and the built environment than any other Scottish university. Web site www.hw.ac.uk

About the FOM Institute for Plasma Physics "Rijnhuizen"

Rijnhuizen is one of the three research institutes of the foundation for Fundamental Research on Matter (FOM), the funding organization for physics in the Netherlands. The FOM Institute for Plasma Physics 'Rijnhuizen' was inaugurated in 1959 with the mission to be the Dutch centre for fusion research. Since then, the scientific programme has included fundamental (experimental and theoretical) plasma physics research and research on fusion technology. Around 1986, it was decided to broaden the mission of Rijnhuizen also beyond plasma physics. This resulted in the start of an activity in quantum electronics in 1987: the development of an infrared Free Electron Laser, FELIX. Since 1993 FELIX is operated as an international user facility delivering annually more than 3000 beam hours to users. Web site www.rijnhuizen.nl