438 research outputs found
Generation of pulsed bipartite entanglement using four-wave mixing
Using four-wave mixing in a hot atomic vapor, we generate a pair of entangled
twin beams in the microsecond pulsed regime near the D1 line of Rb,
making it compatible with commonly used quantum memory techniques. The beams
are generated in the bright and vacuum-squeezed regimes, requiring two separate
methods of analysis, without and with local oscillators, respectively. We
report a noise reduction of up to dB below the standard quantum
limit in the pulsed regime and a level of entanglement that violates an
Einstein--Podolsky--Rosen inequality.Comment: 10 pages, 5 figures, accepted for publication in New Journal Of
Physici
Quantum mutual information of an entangled state propagating through a fast-light medium
Although it is widely accepted that classical information cannot travel
faster than the speed of light in vacuum, the behavior of quantum correlations
and quantum information propagating through actively-pumped fast-light media
has not been studied in detail. To investigate this behavior, we send one half
of an entangled state of light through a gain-assisted fast-light medium and
detect the remaining quantum correlations. We show that the quantum
correlations can be advanced by a small fraction of the correlation time while
the entanglement is preserved even in the presence of noise added by
phase-insensitive gain. Additionally, although we observe an advance of the
peak of the quantum mutual information between the modes, we find that the
degradation of the mutual information due to the added noise appears to prevent
an advancement of the leading edge. In contrast, we show that both the leading
and trailing edges of the mutual information in a slow-light system can be
significantly delayed
Imaging using quantum noise properties of light
We show that it is possible to estimate the shape of an object by measuring
only the fluctuations of a probing field, allowing us to expose the object to a
minimal light intensity. This scheme, based on noise measurements through
homodyne detection, is useful in the regime where the number of photons is low
enough that direct detection with a photodiode is difficult but high enough
such that photon counting is not an option. We generate a few-photon state of
multi-spatial-mode vacuum-squeezed twin beams using four-wave mixing and direct
one of these twin fields through a binary intensity mask whose shape is to be
imaged. Exploiting either the classical fluctuations in a single beam or
quantum correlations between the twin beams, we demonstrate that under some
conditions quantum correlations can provide an enhancement in sensitivity when
estimating the shape of the object
Relative intensity squeezing by four-wave mixing with loss: an analytic model and experimental diagnostic
Four-wave mixing near resonance in an atomic vapor can produce relative
intensity squeezed light suitable for precision measurements beyond the
shot-noise limit. We develop an analytic distributed gain/loss model to
describe the competition of mixing and absorption through the non-linear
medium. Using a novel matrix calculus, we present closed-form expressions for
the degree of relative intensity squeezing produced by this system. We use
these theoretical results to analyze experimentally measured squeezing from a
Rb vapor and demonstrate the analytic model's utility as an experimental
diagnostic.Comment: 10 pages, 5 figure
- …