6,206 research outputs found
Atom detection in a two-mode optical cavity with intermediate coupling: Autocorrelation studies
We use an optical cavity in the regime of intermediate coupling between atom
and cavity mode to detect single moving atoms. Degenerate polarization modes
allow excitation of the atoms in one mode and collection of spontaneous
emission in the other, while keeping separate the two sources of light; we
obtain a higher confidence and efficiency of detection by adding
cavity-enhanced Faraday rotation. Both methods greatly benefit from coincidence
detection of photons, attaining fidelities in excess of 99% in less than 1
microsecond. Detailed studies of the second-order intensity autocorrelation
function of light from the signal mode reveal evidence of antibunched photon
emissions and the dynamics of single-atom transits.Comment: 10 pages, 10 figures, to be published in Phys. Rev.
Applications of computer graphics to aircraft synthesis
The history of the development of an aircraft configuration synthesis program using interactive computer graphics was described. A system based on time-sharing was compared to two different concepts based on distributed computing
Effect of atomic beam alignment on photon correlation measurements in cavity QED
Quantum trajectory simulations of a cavity QED system comprising an atomic
beam traversing a standing-wave cavity are carried out. The delayed photon
coincident rate for forwards scattering is computed and compared with the
measurements of Rempe et al. [Phys. Rev. Lett. 67, 1727 (1991)] and Foster et
al. [Phys. Rev. A 61, 053821 (2000)]. It is shown that a moderate atomic beam
misalignment can account for the degradation of the predicted correlation. Fits
to the experimental data are made in the weak-field limit with a single
adjustable parameter--the atomic beam tilt from perpendicular to the cavity
axis. Departures of the measurement conditions from the weak-field limit are
discussed.Comment: 15 pages and 13 figure
Entangled and disentangled evolution for a single atom in a driven cavity
For an atom in an externally driven cavity, we show that special initial
states lead to near-disentangled atom-field evolution, and superpositions of
these can lead to near maximally-entangled states. Somewhat counterintutively,
we find that (moderate) spontaneous emission in this system actually leads to a
transient increase in entanglement beyond the steady-state value. We also show
that a particular field correlation function could be used, in an experimental
setting, to track the time evolution of this entanglement
From quantum feedback to probabilistic error correction: Manipulation of quantum beats in cavity QED
It is shown how to implement quantum feedback and probabilistic error
correction in an open quantum system consisting of a single atom, with ground-
and excited-state Zeeman structure, in a driven two-mode optical cavity. The
ground state superposition is manipulated and controlled through conditional
measurements and external fields, which shield the coherence and correct
quantum errors. Modeling of an experimentally realistic situation demonstrates
the robustness of the proposal for realization in the laboratory
Development of a machine protection system for the Superconducting Beam Test Facility at Fermilab
Fermilab's Superconducting RF Beam Test Facility currently under construction
will produce electron beams capable of damaging the acceleration structures and
the beam line vacuum chambers in the event of an aberrant accelerator pulse.
The accelerator is being designed with the capability to operate with up to
3000 bunches per macro-pulse, 5Hz repetition rate and 1.5 GeV beam energy. It
will be able to sustain an average beam power of 72 KW at the bunch charge of
3.2 nC. Operation at full intensity will deposit enough energy in niobium
material to approach the melting point of 2500 {\deg}C. In the early phase with
only 3 cryomodules installed the facility will be capable of generating
electron beam energies of 810 MeV and an average beam power that approaches 40
KW. In either case a robust Machine Protection System (MPS) is required to
mitigate effects due to such large damage potentials. This paper will describe
the MPS system being developed, the system requirements and the controls issues
under consideration.Comment: 3 pp. 13th International Conference on Accelerator and Large
Experimental Physics Control Systems (ICALEPCS 2011). 10-14 Oct 2011.
Grenoble, Franc
The three-site Bose-Hubbard model subject to atom losses: the boson-pair dissipation channel and failure of the mean-field approach
We employ the perturbation series expansion for derivation of the reduced
master equations for the three-site Bose-Hubbard model subject to strong atom
losses from the central site. The model describes a condensate trapped in a
triple-well potential subject to externally controlled removal of atoms. We
find that the -phase state of the coherent superposition between the side
wells decays via two dissipation channels, the single-boson channel (similar to
the externally applied dissipation) and the boson-pair channel. The quantum
derivation is compared to the classical adiabatic elimination within the
mean-field approximation. We find that the boson-pair dissipation channel is
not captured by the mean-field model, whereas the single-boson channel is
described by it. Moreover, there is a matching condition between the zero-point
energy bias of the side wells and the nonlinear interaction parameter which
separates the regions where either the single-boson or the boson-pair
dissipation channel dominate. Our results indicate that the -site
Bose-Hubbard models, for , subject to atom losses may require an analysis
which goes beyond the usual mean-field approximation for correct description of
their dissipative features. This is an important result in view of the recent
experimental works on the single site addressability of condensates trapped in
optical lattices.Comment: 9 pages; 3 figures in color; submitted to PR
Managing change – can HR software help?
With the pace of change in the HR and wider business environment seemingly becoming ever-faster, Human Resources
teams have a real challenge on their hands to manage any resulting disruption. Employee engagement and morale is at
stake, not to mention the reputation of HR, and there is significant pressure to justify the financial implications of any change
projects undertaken.
In this white paper, HR thought leaders therefore focus on the subject of best-practice change management, whilst
providing 'real world' examples from the UK's 11th largest housing association, Together Housing. The white paper also
analyses the value of technology to help streamline the potentially disruptive change management process, before sharing
tips and advice for those embarking upon their own change journey
Dramatic impact of pumping mechanism on photon entanglement in microcavity
A theory of entangled photons emission from quantum dot in microcavity under
continuous and pulsed incoherent pumping is presented. It is shown that the
time-resolved two-photon correlations drastically depend on the pumping
mechanism: the continuous pumping quenches the polarization entanglement and
strongly suppresses photon correlation times. Analytical theory of the effect
is presented.Comment: 6 pages, 3 figure
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