854 research outputs found
Strong low-frequency quantum correlations from a four-wave mixing amplifier
We show that a simple scheme based on nondegenerate four-wave mixing in a hot
atomic vapor behaves like a near-perfect phase-insensitive optical amplifier,
which can generate bright twin beams with a measured quantum noise reduction in
the intensity difference of more than 8 dB, close to the best optical
parametric amplifiers and oscillators. The absence of a cavity makes the system
immune to external perturbations, and the strong quantum noise reduction is
observed over a large frequency range.Comment: 4 pages, 4 figures. Major rewrite of the previous version. New
experimental results and further analysi
A Compact Source for Quantum Image Processing with Four-wave Mixing in Rubidium-85
We have built a compact light source for bright squeezed twin-beams at
795\,nm based on four-wave-mixing in atomic Rb vapor. With a total
optical power of 400\,mW derived from a free running diode laser and a tapered
amplifier to pump the four-wave-mixing process, we achieve 2.1\,dB intensity
difference squeezing of the twin beams below the standard quantum limit,
without accounting for losses. Squeezed twin beams generated by the type of
source presented here could be used as reference for the precise calibration of
photodetectors. Transferring the quantum correlations from the light to atoms
in order to generate correlated atom beams is another interesting prospect. In
this work we investigate the dispersion that is generated by the employed
four-wave-mixing process with respect to bandwidth and dependence on probe
detuning. We are currently using this squeezed light source to test the
transfer of spatial information and quantum correlations through media of
anomalous dispersion.Comment: 6 pages, 4 figure
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
Squeezed Light and Entangled Images from Four-Wave-Mixing in Hot Rubidium Vapor
Entangled multi-spatial-mode fields have interesting applications in quantum
information, such as parallel quantum information protocols, quantum computing,
and quantum imaging. We study the use of a nondegenerate four-wave mixing
process in rubidium vapor at 795 nm to demonstrate generation of
quantum-entangled images. Owing to the lack of an optical resonator cavity, the
four-wave mixing scheme generates inherently multi-spatial-mode output fields.
We have verified the presence of entanglement between the multi-mode beams by
analyzing the amplitude difference and the phase sum noise using a dual
homodyne detection scheme, measuring more than 4 dB of squeezing in both cases.
This paper will discuss the quantum properties of amplifiers based on
four-wave-mixing, along with the multi mode properties of such devices.Comment: 11 pages, 8 figures. SPIE Optics and Photonics 2008 proceeding (San
Diego, CA
Light forces in ultracold photoassociation
We study the time-resolved photoassociation of ultracold sodium in an optical
dipole trap. The photoassociation laser excites pairs of atoms to molecular
states of large total angular momentum at high intensities (above 20
kW/cm). Such transitions are generally suppressed at ultracold
temperatures by the centrifugal barriers for high partial waves. Time-resolved
ionization measurements reveal that the atoms are accelerated by the dipole
potential of the photoassociation beam. We change the collision energy by
varying the potential depth, and observe a strong variation of the
photoassociation rate. These results demonstrate the important role of light
forces in cw photoassociation at high intensities.Comment: 7 pages, 3 figure
All-optical generation and photoassociative probing of sodium Bose-Einstein condensates
We demonsatrate an all optical technique to evaporatively produce sodium
Bose-Einstein condensates (BEC). We use a crossed-dipole trap formed from light
near 1060 nm, and a simple ramp of the intensity to force evaporation. In
addition, we introduce photoassociation as diagnostic of the trap loading
process, and show that it can be used to detect the onset of Bose-Einstein
condensation. Finally, we demonstrate the straightforward production of
multiple traps with condensates using this technique, and that some control
over the spinor state of the BEC is achieved by positioning the trap as well.Comment: 8 pages, 10 figure
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