460 research outputs found
Quantum estimation of a damping constant
We discuss an interferometric approach to the estimation of quantum
mechanical damping. We study specific classes of entangled and separable probe
states consisting of superpositions of coherent states. Based on the assumption
of limited quantum resources we show that entanglement improves the estimation
of an unknown damping constant.Comment: 7 pages, 5 figure
New intensity and visibility aspects of a double loop neutron interferometer
Various phase shifters and absorbers can be put into the arms of a double
loop neutron interferometer. The mean intensity levels of the forward and
diffracted beams behind an empty four plate interferometer of this type have
been calculated. It is shown that the intensities in the forward and diffracted
direction can be made equal using certain absorbers. In this case the
interferometer can be regarded as a 50/50 beam splitter. Furthermore the
visibilities of single and double loop interferometers are compared to each
other by varying the transmission in the first loop using different absorbers.
It can be shown that the visibility becomes exactly 1 using a phase shifter in
the second loop. In this case the phase shifter in the second loop must be
strongly correlated to the transmission coefficient of the absorber in the
first loop. Using such a device homodyne-like measurements of very weak signals
should become possible.Comment: 12 pages, 9 figures, accepted for publication in the Journal of
Optics B - Quantum and Semiclassical Optic
On the experimental feasibility of continuous-variable optical entanglement distillation
Entanglement distillation aims at preparing highly entangled states out of a
supply of weakly entangled pairs, using local devices and classical
communication only. In this note we discuss the experimentally feasible schemes
for optical continuous-variable entanglement distillation that have been
presented in [D.E. Browne, J. Eisert, S. Scheel, and M.B. Plenio, Phys. Rev. A
67, 062320 (2003)] and [J. Eisert, D.E. Browne, S. Scheel, and M.B. Plenio,
Annals of Physics (NY) 311, 431 (2004)]. We emphasize their versatility in
particular with regards to the detection process and discuss the merits of the
two proposed detection schemes, namely photo-detection and homodyne detection,
in the light of experimental realizations of this idea becoming more and more
feasible.Comment: 5 pages, 5 figures, contribution to conference proceeding
The Heavy Photon Search Beamline and Its Performance
The Heavy Photon Search (HPS) is an experiment to search for a hidden sector photon, aka a heavy photon or dark photon, in fixed target electroproduction at the Thomas Jefferson National Accelerator Facility (JLab). The HPS experiment searches for the e+e- decay of the heavy photon with bump hunt and detached vertex strategies using a compact, large acceptance forward spectrometer, consisting of a silicon microstrip detector (SVT) for tracking and vertexing, and a PbWO4 electromagnetic calorimeter for energy measurement and fast triggering. To achieve large acceptance and good vertexing resolution, the first layer of silicon detectors is placed just 10cm downstream of the target with the sensor edges only 500 μm above and below the beam. Placing the SVT in such close proximity to the beam puts stringent requirements on the beam profile and beam position stability. As part of an approved engineering run, HPS took data in 2015 and 2016 at 1.05GeV and 2.3GeV beam energies, respectively. This paper describes the beam line and its performance during that data taking
The Heavy Photon Search beamline and its performance
The Heavy Photon Search (HPS) is an experiment to search for a hidden sector
photon, aka a heavy photon or dark photon, in fixed target electroproduction at
the Thomas Jefferson National Accelerator Facility (JLab). The HPS experiment
searches for the ee decay of the heavy photon with bump hunt and
detached vertex strategies using a compact, large acceptance forward
spectrometer, consisting of a silicon microstrip detector (SVT) for tracking
and vertexing, and a PbWO electromagnetic calorimeter for energy
measurement and fast triggering. To achieve large acceptance and good vertexing
resolution, the first layer of silicon detectors is placed just 10 cm
downstream of the target with the sensor edges only 500 m above and below
the beam. Placing the SVT in such close proximity to the beam puts stringent
requirements on the beam profile and beam position stability. As part of an
approved engineering run, HPS took data in 2015 and 2016 at 1.05 GeV and 2.3
GeV beam energies, respectively. This paper describes the beam line and its
performance during that data taking
Engineering cavity-field states by projection synthesis
We propose a reliable scheme for engineering a general cavity-field state.
This is different from recently presented strategies,where the cavity is
supposed to be initially empty and the field is built up photon by photon
through resonant atom-field interactions. Here, a coherent state is previously
injected into the cavity. So, the Wigner distribution function of the desired
state is constructed from that of the initially coherent state. Such an
engineering process is achieved through an adaptation of the recently proposed
technique of projection synthesis to cavity QED phenomena.Comment: 5 ps pages plus 3 included figure
Fresnel Representation of the Wigner Function: An Operational Approach
We present an operational definition of the Wigner function. Our method
relies on the Fresnel transform of measured Rabi oscillations and applies to
motional states of trapped atoms as well as to field states in cavities. We
illustrate this technique using data from recent experiments in ion traps [D.
M. Meekhof et al., Phys. Rev. Lett. 76, 1796 (1996)] and in cavity QED [B.
Varcoe et al., Nature 403, 743 (2000)]. The values of the Wigner functions of
the underlying states at the origin of phase space are W(0)=+1.75 for the
vibrational ground state and W(0)=-1.4 for the one-photon number state. We
generalize this method to wave packets in arbitrary potentials.Comment: 4 pages include 4 figures, submitted to PR
Unique Electron Polarimeter Analyzing Power Comparison and Precision Spin-Based Energy Measurement
Precision measurements of the relative analyzing powers of five electron beam polarimeters, based on Compton, Moller, and Mott scattering, have been performed using the CEBAF accelerator at the Thomas Jefferson National Accelerator Facility ( Jefferson Laboratory). A Wien filter in the 100 keV beam line of the injector was used to vary the electron spin orientation exiting the injector. High statistical precision measurements of the scattering asymmetry as a function of the spin orientation were made with each polarimeter. Since each polarimeter receives beam with the same magnitude of polarization, these asymmetry measurements permit a high statistical precision comparison of the relative analyzing powers of the five polarimeters. This is the first time a precise comparison of the analyzing powers of Compton, Moller, and Mott scattering polarimeters has been made. Statistically significant disagreements among the values of the beam polarization calculated from the asymmetry measurements made with each polarimeter reveal either errors in the values of the analyzing power or failure to correctly include all systematic effects. The measurements reported here represent a first step toward understanding the systematic effects of these electron polarimeters. Such studies are necessary to realize high absolute accuracy (ca. 1%) electron polarization measurements, as required for some parity violation measurements planned at Jefferson Laboratory. Finally, a comparison of the value of the spin orientation exiting the injector that provides maximum longitudinal polarization in each experimental hall leads to an independent and very precise ( better than 10-4) absolute measurement of the final electron beam energy
Bounds on Integrals of the Wigner Function
The integral of the Wigner function over a subregion of the phase-space of a
quantum system may be less than zero or greater than one. It is shown that for
systems with one degree of freedom, the problem of determining the best
possible upper and lower bounds on such an integral, over all possible states,
reduces to the problem of finding the greatest and least eigenvalues of an
hermitian operator corresponding to the subregion. The problem is solved
exactly in the case of an arbitrary elliptical region. These bounds provide
checks on experimentally measured quasiprobability distributions.Comment: 10 pages, 1 PostScript figure, Latex file; revised following
referees' comments; to appear in Physical Review Letter
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