15,611 research outputs found
Nonclassical Moments and their Measurement
Practically applicable criteria for the nonclassicality of quantum states are
formulated in terms of different types of moments. For this purpose the moments
of the creation and annihilation operators, of two quadratures, and of a
quadrature and the photon number operator turn out to be useful. It is shown
that all the required moments can be determined by homodyne correlation
measurements. An example of a nonclassical effect that is easily characterized
by our methods is amplitude-squared squeezing.Comment: 12 pages, 6 figure
Spontaneous decay of excited atomic states near a carbon nanotube
Spontaneous decay process of an excited atom placed inside or outside (near
the surface) a carbon nanotube is analyzed. Calculations have been performed
for various achiral nanotubes. The effect of the nanotube surface has been
demonstrated to dramatically increase the atomic spontaneous decay rate -- by 6
to 7 orders of magnitude compared with that of the same atom in vacuum. Such an
increase is associated with the nonradiative decay via surface excitations in
the nanotube.Comment: 8 pages, 3 figure
Tomographic reconstruction of quantum states in N spatial dimensions
Most quantum tomographic methods can only be used for one-dimensional
problems. We show how to infer the quantum state of a non-relativistic
N-dimensional harmonic oscillator system by simple inverse Radon transforms.
The procedure is equally applicable to finding the joint quantum state of
several distinguishable particles in different harmonic oscillator potentials.
A requirement of the procedure is that the angular frequencies of the N
harmonic potentials are incommensurable. We discuss what kind of information
can be found if the requirement of incommensurability is not fulfilled and also
under what conditions the state can be reconstructed from finite time
measurements. As a further example of quantum state reconstruction in N
dimensions we consider the two related cases of an N-dimensional free particle
with periodic boundary conditions and a particle in an N-dimensional box, where
we find a similar condition of incommensurability and finite recurrence time
for the one-dimensional system.Comment: 8 pages, 1 figur
The first result of the neutrino magnetic moment measurement in the GEMMA experiment
The first result of the neutrino magnetic moment measurement at the
Kalininskaya Nuclear Power Plant (KNPP) with the GEMMA spectrometer is
presented. An antineutrino-electron scattering is investigated. A high-purity
germanium detector of 1.5 kg placed 13.9 m away from the 3 GW reactor core is
used in the spectrometer. The antineutrino flux is . The differential method is used to extract the -e
electromagnetic scattering events. The scattered electron spectra taken in 6200
and 2064 hours for the reactor ON and OFF periods are compared. The upper limit
for the neutrino magnetic moment Bohr magnetons
at 90{%} CL is derived from the data processing.Comment: 9 pages, 10 figures, 2 table
Experimental access to higher-order Zeeman effects by precision spectroscopy of highly charged ions in a Penning trap
We present an experimental concept and setup for laser-microwave
double-resonance spectroscopy of highly charged ions in a Penning trap. Such
spectroscopy allows a highly precise measurement of the Zeeman splittings of
fine- and hyperfine-structure levels due the magnetic field of the trap. We
have performed detailed calculations of the Zeeman effect in the framework of
quantum electrodynamics of bound states as present in such highly charged ions.
We find that apart from the linear Zeeman effect, second- and third-order
Zeeman effects also contribute to the splittings on a level of 10^-4 and 10^-8,
respectively, and hence are accessible to a determination within the achievable
spectroscopic resolution of the ARTEMIS experiment currently in preparation
Evidence for Neutrinoless Double Beta Decay
The data of the Heidelberg-Moscow double beta decay experiment for the
measuring period August 1990 - May 2000 (54.9813 kg y or 723.44 molyears),
published recently, are analyzed using the potential of the Bayesian method for
low counting rates. First evidence for neutrinoless double beta decay is
observed giving first evidence for lepton number violation. The evidence for
this decay mode is 97% (2.2\sigma) with the Bayesian method, and 99.8% c.l.
(3.1\sigma) with the method recommended by the Particle Data Group. The
half-life of the process is found with the Bayesian method to be T_{1/2}^{0\nu}
= (0.8 - 18.3) x 10^{25} y (95% c.l.) with a best value of 1.5 x 10^{25} y. The
deduced value of the effective neutrino mass is, with the nuclear matrix
elements from [Sta90,Tom91] = (0.11 - 0.56) eV (95% c.l.), with a best
value of 0.39 eV. Uncertainties in the nuclear matrix elements may widen the
range given for the effective neutrino mass by at most a factor 2. Our
observation which at the same time means evidence that the neutrino is a
Majorana particle, will be of fundamental importance for neutrino physics.
PACS. 14.69.Pq Neutrino mass and mixing; 23.40.Bw Weak-interaction and lepton
(including neutrino) aspects 23.40.-s Beta decay; double beta decay; electron
and muon capture.Comment: 14 pages, psfile, 7 figures, Published in Modern Physics Letters A,
Vol. 16, No. 37 (2001) 2409-2420, World Scientific Publishing Company, Home
Page: http://ejournals.wspc.com.sg/mpla/16/1637/S0217732301005825.html, Home
Page of Heidelberg Non-Accelerator Particle Physics Group:
http://www.mpi-hd.mpg.de/non_acc
Spontaneous decay of an emitter's excited state near a finite-length metallic carbon nanotube
The spontaneous decay of an excited state of an emitter placed in the
vicinity of a metallic single-wall carbon nanotube (SWNT) was examined
theoretically. The emitter-SWNT coupling strongly depends on the position of
the emitter relative to the SWNT, the length of the SWNT, the dipole transition
frequency and the orientation of the emitter. In the high-frequency regime,
dips in the spectrum of the spontaneous decay rate exist at the resonance
frequencies in the spectrum of the SWNT conductivity. In the
intermediate-frequency regime, the SWNT conductivity is very low, and the
spontaneous decay rate is practically unaffected by the SWNT. In the
low-frequency regime, the spectrum of the spontaneous decay rate contains
resonances at the antennas resonance frequencies for surface-wave propagation
in the SWNT. Enhancement of both the total and radiative spontaneous decay
rates by several orders in magnitude is predicted at these resonance
frequencies. The strong emitter-field coupling is achieved, in spite of the low
Q factor of the antenna resonances, due to the very high magnitude of the
electromagnetic field in the near-field zone. The vacuum Rabi oscillations of
the population of the excited emitter state are exhibited when the emitter is
coupled to an antenna resonance of the SWNT.Comment: 8 pages, 6 figure
Investigations of fast neutron production by 190 GeV/c muon interactions on different targets
The production of fast neutrons (1 MeV - 1 GeV) in high energy muon-nucleus
interactions is poorly understood, yet it is fundamental to the understanding
of the background in many underground experiments. The aim of the present
experiment (CERN NA55) was to measure spallation neutrons produced by 190 GeV/c
muons scattering on carbon, copper and lead targets. We have investigated the
energy spectrum and angular distribution of spallation neutrons, and we report
the result of our measurement of the neutron production differential cross
section.Comment: 19 pages, 11 figures ep
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