3,714 research outputs found
Theory of collective Raman scattering from a Bose-Einstein condensate
Recent experiments have demonstrated superradiant Raman scattering from a
Bose-Einstein condensate driven by a single off-resonant laser beam. We present
a quantum theory describing this phenomenon, showing Raman amplification of
matter wave due to collective atomic recoil from 3-level atoms in a
-configuration. When atoms are initially in a single lower internal
state, a closed two-level system is realized between atoms with different
internal states, and entangled atom-photon pairs can be generated. When atoms
are initially prepared in both the lower internal states, a fraction of atoms
recoiling in the backward direction can be generated.Comment: 5 pages, 2 figure
Non-classical Photon Statistics For Two-mode Optical Fields
The non-classical property of subpoissonian photon statistics is extended
from one to two-mode electromagnetic fields, incorporating the physically
motivated property of invariance under passive unitary transformations.
Applications to squeezed coherent states, squeezed thermal states, and
superposition of coherent states are given. Dependences of extent of
non-classical behaviour on the independent squeezing parameters are graphically
displayed.Comment: 15 pages, RevTex, 5 figures, available by sending email to
[email protected]
Number-Phase Wigner Representation for Efficient Stochastic Simulations
Phase-space representations based on coherent states (P, Q, Wigner) have been
successful in the creation of stochastic differential equations (SDEs) for the
efficient stochastic simulation of high dimensional quantum systems. However
many problems using these techniques remain intractable over long integrations
times. We present a number-phase Wigner representation that can be unraveled
into SDEs. We demonstrate convergence to the correct solution for an anharmonic
oscillator with small dampening for significantly longer than other phase space
representations. This process requires an effective sampling of a non-classical
probability distribution. We describe and demonstrate a method of achieving
this sampling using stochastic weights.Comment: 7 pages, 1 figur
Intensity fluctuations in steady state superradiance
Alkaline-earth like atoms with ultra-narrow optical transitions enable
superradiance in steady state. The emitted light promises to have an
unprecedented stability with a linewidth as narrow as a few millihertz. In
order to evaluate the potential usefulness of this light source as an
ultrastable oscillator in clock and precision metrology applications it is
crucial to understand the noise properties of this device. In this paper we
present a detailed analysis of the intensity fluctuations by means of
Monte-Carlo simulations and semi-classical approximations. We find that the
light exhibits bunching below threshold, is to a good approximation coherent in
the superradiant regime, and is chaotic above the second threshold.Comment: 8 pages, 5 figure
Spatial fluctuations in an optical parametric oscillator below threshold with an intracavity photonic crystal
We show how to control spatial quantum correlations in a multimode degenerate
optical parametric oscillator type I below threshold by introducing a spatially
inhomogeneous medium, such as a photonic crystal, in the plane perpendicular to
light propagation. We obtain the analytical expressions for all the
correlations in terms of the relevant parameters of the problem and study the
number of photons, entanglement, squeezing, and twin beams. Considering
different regimes and configurations we show the possibility to tune the
instability thresholds as well as the quantumness of correlations by breaking
the translational invariance of the system through a photonic crystal
modulation.Comment: 12 pages, 7 figure
High-Fidelity Readout in Circuit Quantum Electrodynamics Using the Jaynes-Cummings Nonlinearity
We demonstrate a qubit readout scheme that exploits the Jaynes-Cummings
nonlinearity of a superconducting cavity coupled to transmon qubits. We find
that in the strongly-driven dispersive regime of this system, there is the
unexpected onset of a high-transmission "bright" state at a critical power
which depends sensitively on the initial qubit state. A simple and robust
measurement protocol exploiting this effect achieves a single-shot fidelity of
87% using a conventional sample design and experimental setup, and at least 61%
fidelity to joint correlations of three qubits.Comment: 5 pages, 4 figure
Low-energy electron scattering by tetrahydrofuran
Cross sections for elastic scattering of low-energy electrons by tetrahydrofuran, a prototype for the furanose ring found in the backbone of DNA, have been measured and calculated over a wide energy range, with an emphasis on energies below 6 eV, where previous data are scarce. The measurements employ a thin-aperture version of the relative-flow method, while the calculations employ the Schwinger multichannel method with an extensive treatment of polarization effects. Comparisons with earlier results, both experimental and theoretical, are presented and discussed. A proper accounting for the strong permanent electric dipole of tetrahydrofuran is found to be essential to obtaining reliable cross sections, especially at energies below 5 eV
Paired atom laser beams created via four-wave mixing
A method to create paired atom laser beams from a metastable helium atom
laser via four-wave mixing is demonstrated. Radio frequency outcoupling is used
to extract atoms from a Bose Einstein condensate near the center of the
condensate and initiate scattering between trapped and untrapped atoms. The
unequal strengths of the interactions for different internal states allows an
energy-momentum resonance which leads to the creation of pairs of atoms
scattered from the zero-velocity condensate. The resulting scattered beams are
well separated from the main atom laser in the 2-dimensional transverse atom
laser profile. Numerical simulations of the system are in good agreement with
the observed atom laser spatial profiles, and indicate that the scattered beams
are generated by a four-wave mixing process, suggesting that the beams are
correlated.Comment: 5 pages, 3 figure
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