Quantum Information Group, Single Photon LED
We have developed the world's first light emitting diode (LED) capable of emitting a stream of single photons. A photon is the smallest unit, or 'particle', of light. Why do we want to produce the world's dimmest light bulb? This nanotechnology will enable many new applications in the field of quantum information technology, such as quantum cryptography and computing. Indeed, many people believe that a cheap and easy to use single photon source will enable a wide gambit of quantum light applications, in much the same way as the laser facilitated the exploitation of classical light in applications such as fibre optic communications used for telephony and the internet, bar code scanning and range finding.
Light is already used as a carrier of information over optical fibres. However, many of the ideas to exploit the quantum mechanical properties of light require a source where the emission can be regulated at the level of individual photons. The first commercial applications of a single photon LED are likely to be in unconditionally secure quantum key distribution. Toshiba is already developing such a system.
Our single photon LED makes use of the optical emission from a single quantum dot. The idea is quite straightforward: a quantum dot is a single quantum system so it can hold just one electron in a particular excited energy level. Quantum dots emit light whenever electrons in an excited energy level relax to a lower energy level. However, since our LED isolates the emission of a single quantum dot, which can hold just one excited electron at a time, photons will be emitted from the device one-by-one. If we excite the dot with a train of short voltages pulse, it will emit a train of single photons.
This device is the first electrically driven single photon source. Electrical injection of the recombining carriers is essential for realizing a practical device that is robust, compact and cost-effective.
Further Reading
| 1 |
Technical |
 Electrically driven single photon source
by Z Yuan et al |
Science 295, pp. 102–105 (2002) |
| 2 |
Technical |
Variable frequency single photon emitting diode
by M B Ward et al |
Physics of Semiconductors 2002
Institute of Physics Conference Series Number 171 edited by A R Long and J H Davies |
| 3 |
Technical review |
Generation of single photons using semiconductor quantum dots
by A J Shields et al |
Nano-physics and Bioelectronics: A New Odyssey (Elsevier, Amsterdam, 2002) |
| 4 |
Easy |
Paving the way for ‘uncrackable’ codes
by Ivan Noble |
BBC News (13 Dec 2001) |
| 5 |
Easy |
Little lamp may set quantum tech aglow
by P Weiss |
Science News (15 Dec 2001) |
| 6 |
Easy |
Unhackable quantum cryptography |
Nikkei (14 Dec 2001) |
