2,372 research outputs found
Generation of Rb-resonant bright two-mode squeezed light with four-wave mixing
Squeezed states of light have found their way into a number of applications
in quantum-enhanced metrology due to their reduced noise properties. In order
to extend such an enhancement to metrology experiments based on atomic
ensembles, an efficient light-atom interaction is required. Thus, there is a
particular interest in generating narrow-band squeezed light that is on atomic
resonance. This will make it possible not only to enhance the sensitivity of
atomic based sensors, but also to deterministically entangle two distant atomic
ensembles. We generate bright two-mode squeezed states of light, or twin beams,
with a non-degenerate four-wave mixing (FWM) process in hot Rb in a
double-lambda configuration. Given the proximity of the energy levels in the D1
line of Rb and Rb, we are able to operate the FWM in Rb in
a regime that generates two-mode squeezed states in which both modes are
simultaneously on resonance with transitions in the D1 line of Rb, one
mode with the to transition and the other one with the to
transition. For this configuration, we obtain an intensity difference
squeezing level of dB. Moreover, the intensity difference squeezing
increases to dB and dB when only one of the modes of the squeezed
state is resonant with the D1 to or to transition of
Rb, respectively
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
Effect of Closely-Spaced Excited States on Electromagnetically Induced Transparency
Electromagnetically induced transparency (EIT) is a well-known phenomenon due
in part to its applicability to quantum devices such as quantum memories and
quantum gates. EIT is commonly modeled with a three-level lambda system due to
the simplicity of the calculations. However, this simplified model does not
capture all the physics of EIT experiments with real atoms. We present a
theoretical study of the effect of two closely-spaced excited states on EIT and
off-resonance Raman transitions. We find that the coherent interaction of the
fields with two excited states whose separation is smaller than their Doppler
broadened linewidth can enhance the EIT transmission and broaden the width of
the EIT peak. However, a shift of the two-photon resonance frequency for
systems with transitions of unequal dipole strengths leads to a reduction of
the maximum transparency that can be achieved when Doppler broadening is taken
into account even under ideal conditions of no decoherence. As a result,
complete transparency cannot be achieved in a vapor cell. Only when the
separation between the two excited states is of the order of the Doppler width
or larger can complete transparency be recovered. In addition, we show that
off-resonance Raman absorption is enhanced and its resonance frequency is
shifted. Finally, we present experimental EIT measurements on the D1 line of
Rb that agree with the theoretical predictions when the interaction of
the fields with the four levels is taken into account
Atomic Resonant Single-Mode Squeezed Light from Four-Wave Mixing through Feedforward
Squeezed states of light have received renewed attention due to their
applicability to quantum-enhanced sensing. To take full advantage of their
reduced noise properties to enhance atomic-based sensors, it is necessary to
generate narrowband near or on atomic resonance single-mode squeezed states of
light. We have previously generated bright two-mode squeezed states of light,
or twin beams, that can be tuned to resonance with the D1 line of Rb
with a non-degenerate four-wave mixing (FWM) process in a double-lambda
configuration in a Rb vapor cell. Here we report on the use of
feedforward to transfer the amplitude quantum correlations present in the twin
beams to a single beam for the generation of single-mode amplitude squeezed
light. With this technique we obtain a single-mode squeezed state with a
squeezing level of dB when it is tuned off-resonance and a level
of dB when it is tuned on resonance with the D1 to
transition of Rb
Einstein-Podolsky-Rosen Paradox with Position-Momentum Entangled Macroscopic Twin Beams
Spatial entanglement is at the heart of quantum enhanced imaging applications
and high-dimensional quantum information protocols. In particular, for imaging
and sensing applications, quantum states with a macroscopic number of photons
are needed to provide a real advantage over the classical state-of-the-art. We
demonstrate the Einstein-Podolsky-Rosen (EPR) paradox in its original position
and momentum form with bright twin beams of light by showing the presence of
EPR spatial (position-momentum) entanglement. An electron-multiplying
charge-coupled-device camera is used to record images of the bright twin beams
in the near and far field regimes to achieve an apparent violation of the
uncertainty principle by more than an order of magnitude. We further show that
the presence of quantum correlations in the spatial and temporal degrees of
freedom leads to spatial squeezing between the spatial fluctuations of the
bright twin beams in both the near and far fields. This provides another
verification of the spatial entanglement and points to the presence of
hyperentanglement in the bright twin beams.Comment: 5 pages, 3 Figures. Includes Supplemental Materia
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