Cambridge 24 May 2005

Researchers at Toshiba Research Europe Ltd (TREL) in Cambridge will announce this week that they have developed a light source that can be used to send single photons in a regular stream through optical fibre over long distances. The device is needed for future quantum networks exploiting the particle-like properties of light. The results will be announced at the prestigious Quantum Electronics and Laser Science (QELS) Conference in Baltimore this week.

The team has achieved the breakthrough by developing a semiconductor nanotechnology tailored for use with ordinary telecom fibre cables. It results from an initiative funded by the Department of Trade and Industry involving TREL, University of Cambridge and Imperial College London.

The worlds dimmest fibre source contains a tiny ‘quantum dot' of semiconductor, measuring just 45 nm in diameter and 10nm in height, which emits photons (the particles of light) one at a time. By manipulating the way in which the dot was formed, the emitted photons were tuned to a wavelength that allows long distance propagation in ordinary fibre optic cables.

Dr Andrew Shields, head of the Quantum Information Group at TREL comments: "Exploiting the quantum properties of light allows us to communicate and process information in ways that have not been possible previously. A good example is in quantum cryptography, which allows us to verify the secrecy of information sent on single photons.”

“These developments show that single photon sources can now be applied to real communication systems," he added.

Prof Will Stewart, Chairman of Innos, formerly Chief Scientist at Marconi and who monitors progress in the project for DTI, adds “Quantum is nature's digital information system - and the natural goal for our own digital systems. The team is to be congratulated on making a significant step along this road.”

Single photon sources are needed for future applications in quantum information technology, such as quantum cryptography, a technique to distribute secret digital keys on a fibre-optic network. Here a single-photon source is required to improve the security and bit rate of current systems, which rely on strongly attenuated lasers to simulate single photon pulses. TREL, who have already developed a robust system for quantum key distribution, confirmed that the performance of the developed single photon source is sufficient for real applications and plan to integrate the device in their system within the next year.

TRELs work on single photon devices is funded in part by the Department of Trade and Industry/Engineering and Physical Sciences Research Council ‘Optical Systems for the Digital Age' and European Commission ‘Information Society Technologies' programmes.

Ian Williams, Programme Manager for the DTI's LINK Optical Systems Programme, said “This is a most impressive achievement from one of the most ambitious and technically challenging projects we supported under the LINK Optical Systems Programme. This advance now offers the prospect of great improvements in IT security with potential benefits to IT users worldwide."

About Toshiba Corporation Toshiba Corporation is a leader in information and communications systems, electronic components, consumer products and power systems. The company's integration of these wide-ranging capabilities assures its position as an innovator in advanced components, products and systems. Toshiba has more than 161,000 employees worldwide and annual sales of US$53 billion (FY2003). About Toshiba Research Europe Ltd Toshiba Corporation is fully committed to the research and development of future technologies. This commitment has resulted in Toshiba having a record number of world firsts, including the first laptop PC (1985), the first single chip MPEG4 videophone LSI (1998) and the first DVD player (Oct. 1998). Over the next 3 years to end March 2006, the Corporation anticipates a total global R&D expenditure of ¥1,100bn ($9.3bn). Toshiba Corporation established its first overseas research centre in 1991, with the opening of Toshiba Cambridge Research Centre Ltd in the UK. This was renamed Toshiba Research Europe Ltd (TREL) in August 1998, when a new telecommunications laboratory in Bristol was launched. TREL now has two research laboratories in the UK; the Cambridge Research Laboratory (CRL) in Cambridge, and Telecommunications Research Laboratory (TRL) in Bristol. With security of information more critical than ever, Toshiba's Quantum Information Group is working on techniques for secure communication based on quantum cryptography. The team has already achieved a number of world firsts including the realization of the first link exceeding 100km and a unique hardware management system that allows continuous operation. They have also pioneered a single photon generation and detection technology based on semiconductor quantum dots.

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