Once it has emerged from the cavity,
the second photon has two possible states
– delayed or extra-delayed – depending
upon whether another photon preceded it.
The cavity thus serves as a quantum
switch, the fundamental building block of
a quantum computer. The work was described in the Sept. 2 issue of Science
Currently, the team says, the extra delay
is not quite long enough to distinguish the
delayed photons from the extra-delayed
Squeezed light helps measure gravitational waves
HANNOVER, Germany – A new
“squeezed light” method improves the
sensitivity and accuracy of the interferometers used to measure gravitational waves.
Observing the gravitational waves that
result from supernova explosions and
other cosmic events requires extremely
sensitive metrology techniques. A gravita-
tional wave’s signal is so small that it is
usually dwarfed by the noise generated by
the quantum mechanical fluctuations of
the light beams, and this shot noise limits
the accuracy of the interferometer.
3-D visualization of gravitational waves produced by two orbiting black holes. Courtesy of Henze, NASA.
A highly complex laser system produces light in the
gravitational wave detector GEO600 that is particularly quiet. Courtesy of Max Planck Institute for