24,179 research outputs found
Limit on T-violating P-conserving rhoNN interaction from the gamma decay of Fe-57
We use the experimental limit on the interference of M1 and E2 multipoles in the γ decay of 57Fe to bound the time-reversal-violating parity-conserving ρNN vertex. Our approach is a large-basis shell-model calculation of the interference. We find an upper limit on the parameter g¯ρ, the relative strength of the T-violating ρNN vertex, of close to 10^(-2), a value similar to the best limits from other experiments
Space shuttle navigation analysis. Volume 1: GPS aided navigation
Analytical studies related to space shuttle navigation are presented. Studies related to the addition of NAVSTAR Global Positioning System user equipment to the shuttle avionics suite are presented. The GPS studies center about navigation accuracy covariance analyses for both developmental and operational phases of GPS, as well as for various orbiter mission phases
Entanglement signature in the mode structure of a single photon
It is shown that entanglement, which is a quantum correlation property of at
least two subsystems, is imprinted in the mode structure of a single photon.
The photon, which is emitted by two coupled cavities, carries the information
on the concurrence of the two intracavity fields. This can be useful for
recording the entanglement dynamics of two cavity fields and for entanglement
transfer.Comment: 4 pages, 3 figure
Experimental determination of a nonclassical Glauber-Sudarshan P function
A quantum state is nonclassical if its Glauber-Sudarshan P function fails to
be interpreted as a probability density. This quantity is often highly
singular, so that its reconstruction is a demanding task. Here we present the
experimental determination of a well-behaved P function showing negativities
for a single-photon-added thermal state. This is a direct visualization of the
original definition of nonclassicality. The method can be useful under
conditions for which many other signatures of nonclassicality would not
persist.Comment: 4 pages, 4 figure
Implementation of three-qubit Toffoli gate in a single step
Single-step implementations of multi-qubit gates are generally believed to
provide a simpler design, a faster operation, and a lower decoherence. For
coupled three qubits interacting with a photon field, a realizable scheme for a
single-step Toffoli gate is investigated. We find that the three qubit system
can be described by four effective modified Jaynes-Cummings models in the
states of two control qubits. Within the rotating wave approximation, the
modified Jaynes-Cummings models are shown to be reduced to the conventional
Jaynes-Cummings models with renormalized couplings between qubits and photon
fields. A single-step Toffoli gate is shown to be realizable with tuning the
four characteristic oscillation periods that satisfy a commensurate condition.
Possible values of system parameters are estimated for single-step Toffli gate.
From numerical calculation, further, our single-step Toffoli gate operation
errors are discussed due to imperfections in system parameters, which shows
that a Toffoli gate with high fidelity can be obtained by adjusting pairs of
the photon-qubit and the qubit-qubit coupling strengthes. In addition, a
decoherence effect on the Toffoli gate operation is discussed due to a thermal
reservoir.Comment: 8 pages, 4 figures, to appear in PR
Neutron-Proton Correlations in an Exactly Solvable Model
We examine isovector and isoscalar neutron-proton correlations in an exactly
solvable model based on the algebra SO(8). We look particularly closely at
Gamow-Teller strength and double beta decay, both to isolate the effects of the
two kinds of pairing and to test two approximation schemes: the renormalized
neutron-proton QRPA (RQRPA) and generalized BCS theory. When isoscalar pairing
correlations become strong enough a phase transition occurs and the dependence
of the Gamow-Teller beta+ strength on isospin changes in a dramatic and
unfamiliar way, actually increasing as neutrons are added to an N=Z core.
Renormalization eliminates the well-known instabilities that plague the QRPA as
the phase transition is approached, but only by unnaturally suppressing the
isoscalar correlations. Generalized BCS theory, on the other hand, reproduces
the Gamow-Teller strength more accurately in the isoscalar phase than in the
usual isovector phase, even though its predictions for energies are equally
good everywhere. It also mixes T=0 and T=1 pairing, but only on the isoscalar
side of the phase transition.Comment: 13 pages + 11 postscript figures, in RevTe
Quantum Correlations from the Conditional Statistics of Incomplete Data
We study, in theory and experiment, the quantum properties of correlated
light fields measured with click-counting detectors providing incomplete
information on the photon statistics. We establish a correlation parameter for
the conditional statistics, and we derive the corresponding nonclassicality
criteria for detecting conditional quantum correlations. Classical bounds for
Pearson's correlation parameter are formulated that allow us, once they are
violated, to determine nonclassical correlations via the joint statistics. On
the one hand, we demonstrate nonclassical correlations in terms of the joint
click statistics of light produced by a parametric down conversion source. On
the other hand, we verify quantum correlations of a heralded, split
single-photon state via the conditional click statistics together with a
generalization to higher-order moments. We discuss the performance of the
presented nonclassicality criteria to successfully discern joint and
conditional quantum correlations. Remarkably, our results are obtained without
making any assumptions on the response function, quantum efficiency, and
dark-count rate of the photodetectors
Thickness-dependent secondary structure formation of tubelike polymers
By means of sophisticated Monte Carlo methods, we investigate the
conformational phase diagram of a simple model for flexible polymers with
explicit thickness. The thickness constraint, which is introduced geometrically
via the global radius of curvature of a polymer conformation, accounts for the
excluded volume of the polymer and induces cooperative effects supporting the
formation of secondary structures. In our detailed analysis of the temperature
and thickness dependence of the conformational behavior for classes of short
tubelike polymers, we find that known secondary-structure segments like helices
and turns, but also ringlike conformations and stiff rods are dominant
intrinsic topologies governing the phase behavior of such cooperative tubelike
objects. This shows that the thickness constraint is indeed a fundamental
physical parameter that allows for a classification of generic polymer
structures
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