Press Release: Toshiba makes major advance in quantum computing

Toshiba Research Europe Ltd., Cambridge Research Laboratory
Toshiba makes major advance in quantum computing
Cambridge 16 June 2008

• First practical device to count the number of photons in light signals
• Important breakthrough for Quantum Information Technologies

Scientists at Toshiba Research Europe Limited have developed the first practical semiconductor device that can count the particles (or photons) in light signals.

The new device is a significant step towards creating viable quantum computers and communication systems, which exploit the particle-like properties of light. Determining the number of photons in a light signal is of crucial importance for many of these applications.

Quantum computers based on photons, for example, need to distinguish between one and two photons on each output. Another application where this is important is for quantum teleportation, which may be used to send secret digital keys over longer distances than currently possible.

The lack of a suitable photon number resolving detector has been a major obstacle to real-world deployment of quantum technologies. Although some alternative technologies have shown limited photon number resolving capability in the lab, they all required cryogenic cooling (to 4 Kelvin, or Minus 269 degrees Celsius) and often had low efficiency, a small active area or long integration times which rendered them impractical.

Until now the most common semiconductor detector, the avalanche photo-diode, has been able to register only the presence or absence of one or more photons. The new compact, easy-to-use detector developed by Toshiba, however, is able to count the number of individual photons in a pulse; the first practical device with this capability. It is expected to accelerate the development of quantum information technologies.

The breakthrough is a result of a new technique developed by Toshiba to detect weak photon-induced avalanches. The electrical current caused by a single photon in a semiconductor is much too weak to be detected quickly. Avalanche photo-diodes work by amplifying this tiny current million-fold using an avalanche effect to multiply the strength of the current. Usually, however, the strength of the final current does not depend on the number of photons that initiated it. The Toshiba device can detect photon-induced avalanches that are 20 times weaker than conventionally, and the strength of which scale linearly with the incident number of photons.

Dr Andrew Shields, Leader of the Quantum Information Group commented, “A simple semiconductor device that can count the photons in a light signal is important for several quantum applications. We plan to apply the new device, in conjunction with our semiconductor photon source technology, in practical quantum communication gates that can extend the distance of quantum key distribution and in quantum computers based on photons.”

The breakthrough is reported today in the scientific journal Nature Photonics.

For further information about the work of Toshiba CRL, go to

About Toshiba

Toshiba is a world leader and innovator in pioneering high technology, a diversified manufacturer and marketer of advanced electronic and electrical products spanning information & communications equipment and systems; digital consumer products; electronic devices and components; power systems; industrial and social infrastructure systems; and home appliances. In the social infrastructure systems business, Toshiba contributes to society with cutting edge infrastructure management systems and solutions, including radio application systems and broadcasting and network systems.

Toshiba was founded in 1875, and today operates a global network of more than 670 companies, with over 191,000 employees worldwide and annual sales surpassing US$60 billion. Visit Toshiba’s web site at

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. 1996). Over the next 3 years to end March 2010, the Corporation anticipates a total global R&D expenditure of JPY1,290bn.

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.



~ by vascoteixeira on August 29, 2008.

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