A superconducting single-photon detector has been built by a Russian-US
collaboration (Roman Sobolewski, University of Rochester, 716-275-1551,
sobolewski@ece.rochester.edu), offering immediate applications in testing
computer chips and more speculative applications for Mars-Earth communications.
The researchers fabricated extremely thin strips of niobium nitride,
a metallic compound that becomes superconducting in liquid helium near
absolute zero. Then, they made a detector based on these strips, each
only a micron wide and several atoms thick.
The detector enabled the researchers to observe single visible and
infrared photons. That's because the superconducting strips lack the
electrical noise that ordinarily obscures a single-photon signal.
The detector can record the small amount of infrared light that is
released when a transistor switches on or off. A California company
is using the detector for this purpose. Since the detector can detect
bursts as short as picoseconds, they can determine whether or not high-speed
transistors are switching on at the right time.
In more speculative applications, this detector could be employed as
an efficient detector of optical signals for wireless communications
between Mars and Earth. (Gol'tsman
et al., Applied Physics Letters, 6 August 2001; also
see Rochester
press release.)
