6 research outputs found
Observation of -9 dB quadrature squeezing with improvement of phase stability in homodyne measurement
We observe -9.010.14 dB of squeezing and +15.120.14 dB of
antisqueezing with a local oscillator phase locked in homodyne measurement. In
reference [1], two main factors are pointed out which degrade the observed
squeezing level: phase fluctuation in homodyne measurement and intracavity
losses of an optical parametric oscillator for squeezing. We have improved the
phase stability of homodyne measurement and have reduced the intracavity
losses. We measure pump power dependences of the squeezing and antisqueezing
levels, which show good agreement with theoretical calculations taking account
of the phase fluctuation.Comment: 4 pages, 4 figure
Experimental generation of four-mode continuous-variable cluster states
Continuous-variable Gaussian cluster states are a potential resource for
universal quantum computation. They can be efficiently and unconditionally
built from sources of squeezed light using beam splitters. Here we report on
the generation of three different kinds of continuous-variable four-mode
cluster states. In our realization, the resulting cluster-type correlations are
such that no corrections other than simple phase-space displacements would be
needed when quantum information propagates through these states. At the same
time, the inevitable imperfections from the finitely squeezed resource states
and from additional thermal noise are minimized, as no antisqueezing components
are left in the cluster states.Comment: 5 pages, 4 figure
Experimental Demonstration of Macroscopic Quantum Coherence in Gaussian States
We witness experimentally the presence of macroscopic coherence in Gaussian
quantum states using a recently proposed criterion (E.G. Cavalcanti and M.
Reid, Phys. Rev. Lett. 97, 170405 (2006)). The macroscopic coherence stems from
interference between macroscopically distinct states in phase space and we
prove experimentally that even the vacuum state contains these features with a
distance in phase space of shot noise units (SNU). For squeezed
states we found macroscopic superpositions with a distance of up to
SNU. The proof of macroscopic quantum coherence was investigated
with respect to squeezing and purity of the states.Comment: 5 pages, 6 figure