A single-photon LED, a light-emitting diode that fires one photon at
a time, has been created, offering a potentially inexpensive and easy-to-manufacture
component for quantum cryptography and a host of other applications.
At the CLEO/QELS meeting last week in Long Beach, scientists at Toshiba
Research Europe Limited described a tiny, nanometer-scale indium arsenide
quantum dot embedded in a gallium arsenide LED structure.
The quantum dot is so small that it can at most capture a few electrons
and holes from a pulse of electric current. A single photon is created
by the recombination of a single electron and single hole in the dot.
The researchers believe this is the first electrically driven single-photon
source. Such single-particle-emitting sources are essential for a truly
secure form of quantum cryptography. Otherwise, if several photons spill
out from a device at a time, the extra ones can be siphoned off by an
eavesdropper, who could then intercept a message without being detected.
(Paper QTuG1 at meeting; contact Andrew Shields, firstname.lastname@example.org;
see also Yuan et al., Science,
4 January 2002.)