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1.
H. Prakash P. Kumar 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(2):359-363
We study amplitude-squared squeezing of the Hermitian operator Zθ=Z1
cosθ+Z2 sin θ, in the most general superposition state
, of two coherent states
and
. Here operators Z1,2 are defined by
, a is annihilation operator, θ is angle, and
complex numbers C1,2 , α, β are arbitrary and only
restriction on these is the normalization condition of the state
. We define the condition for a state
to be amplitude-squared squeezed for the operator Zθ
if squeezing parameter
, where N=a+a and
. We find
maximum amplitude-squared squeezing of Zθ in the superposed
coherent state
with minimum value 0.3268 of the
parameter S for an infinite combinations with α- β= 2.16
exp [±i(π/4) + iθ/2],
and with
arbitrary values of (α+β) and θ. For this minimum
value of squeezing parameter S, the expectation value of photon number can
vary from the minimum value 1.0481 to infinity. Variations of the parameter
S with different variables at maximum amplitude-squared squeezing are also
discussed. 相似文献
2.
O. Jedrkiewicz R. Loudon J. Jeffers 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,39(1):129-140
Previous work on the retrodictive theory of direct
detection is extended to cover the homodyne detection of coherent optical
signal states
and
. The retrodictive input state probabilities are obtained by
the application of Bayes' theorem to the corresponding predictive
distributions, based on the probability operator measure (POM) elements for
the homodyne process. Results are derived for the retrodictive information
on the complex amplitude of the signal field obtainable from the difference
photocount statistics of both 4-port and 8-port balanced homodyne detection
schemes. The local oscillator is usually assumed much stronger than the
signal but the case of equal strengths in 4-port detection is also
considered. The calculated probability distributions and error rates are
illustrated numerically for values of signal and local oscillator strengths
that extend from the classical to the quantum regimes. 相似文献
3.
H. Prakash R. Kumar 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(3):475-481
Saito and Ueda [Phys. Rev. A 59, 3959 (1999)] studied atomic and
radiation squeezing in interaction of a single mode coherent state
of radiation with two excited two-level atoms, using
the Jaynes Cummings Hamiltonian. They considered α real and studied
squeezing of the Dicke operator Sx using the Kitagawa-Ueda criterion for
squeezing and coupling times less than or nearly equal to
. We obtain results to all orders in coupling time for
atoms, which are initially in (i) fully excited, (ii) superradiant or in
(iii) ground states and obtain more general results. We use our recently
reported criterion for atomic squeezing, of which the Kitagawa-Ueda
criterion is a special case, and obtain a much stronger (nearly 95%)
atomic squeezing than that (nearly 1.1%) reported by Saito and Ueda. 相似文献
4.
P. F. Yu J. G. Cai J. M. Liu G. T. Shen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(1):151-158
We investigate the phase decoherence effects on
the entanglement of a two-qubit anisotropic Heisenberg
model
with a nonuniform magnetic field in the x–z-plane. As a
measure of the entanglement, the concurrence of the system is
calculated. It is shown that when the magnetic field is along the
z-axis, the nonuniform and uniform components of the field have
no influence on the entanglement for the cases of
and
, respectively. But when
the magnetic field is not along the z-axis, both the uniform and
the nonuniform components of the field will introduce the
decoherence effects. It is found that the effects of the
Heisenberg chain's anisotropy in the Z-direction on the
entanglement are dependent on the direction of the field.
Moreover, the larger the initial concurrence is, the higher value
it will exhibit during the time evolution of the system for a
proper set of the parameters ν, Δ, θ, γ
, B and b. 相似文献
5.
Hyperfine structure and isotope shifts in five optical
transitions: 424.5 nm (
–
), 537.2 nm (
–
), 554.5 nm
(
–
), 560.9 nm
(
–
) and 666.0 nm
(
–
)
of Pb II have been measured. As a light source the discharge tube was used.
The hyperfine structure measurements were
performed using metallic isotope 207Pb. For isotope shifts
measurements natural lead was used. The high resolution spectral apparatus consisted of a silver
coated Fabry-Perot etalon and a grating spectrograph combined
with a CCD camera used as a detector. In the analysis of the
spectra a computer simulation technique was used. The hyperfine
structure observations yielded the splitting constants A for
seven levels of Pb II. The isotope shift studies enabled to
separate the mass and the field shifts and to determine values of
changes of the mean square nuclear charge radii. 相似文献
6.
A. Ehresmann W. Kielich L. Werner Ph. V. Demekhin D. V. Omel''yanenko V. L. Sukhorukov K.-H. Schartner H. Schmoranzer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(2):235-246
Dispersed fluorescence from fragments formed after the de-excitation of the
1s-1π* resonances of N*O and NO* has been
measured in the spectral range of 118–142 nm. This range is dominated by
lines of atomic nitrogen and oxygen fragments and by the
bands in the NO+ ion which result from the participator Auger decay of the 1s-1π* resonances.
Ab-initio calculations of the transition probabilities between vibrational
levels during the reaction NO
N*O
⇒ NO
were used to explain the observed intensity dependence for the
fluorescence bands on the exciting-photon energy across
the resonances and on both v′ and v′′
vibrational quantum numbers. The multiplet structure of the 1s-1π* resonance and lifetime vibrational interference explain the observed exciting-photon energy dependence of the
fluorescence
intensity. A strong spin-orbit coupling between singlet and triplet states
of NO+ is proposed to reduce additional cascade population of the
state via radiative transitions from the
and
states and to explain
remaining differences between measured and calculated integral fluorescence
intensities. 相似文献
7.
For a homogeneous quantum network of N subsystems with n levels each we consider separable generalized Werner states. A generalized Werner state is defined as a mixture of the totally mixed state and an arbitrary pure state
:
with a mixture coefficient
. For this density operator
to be separable,
will have an upper bound
. Below this bound one should alternatively be able to reproduce
by a mixture of entirely separable input-states. For this purpose we introduce a set of modules, each contributing elementary coherence properties with respect to a generalized coherence vector. Based on these there exists a general step-by-step mixing process for any
. For
being a cat-state it is possible to define an optimal process, which produces states right up to the separability boundary (
).Received: 3 December 2002, Published online: 29 July 2003PACS:
03.65.Ud Entanglement and quantum nonlocality (e.g. EPR paradox, Bells inequalities, GHZ states, etc.) - 03.67.-a Quantum information - 03.65.-w Quantum mechanics 相似文献
8.
G. Poletti F. Orsini D. Batani A. Bernardinello T. Desai J. Ullschmied J. Skala B. Kralikova E. Krousky L. Juha M. Pfeifer Ch. Kadlec T. Mocek A. Präg O. Renner F. Cotelli C. Lora Lamia A. Zullini 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2004,30(2):235-241
Soft X-ray Contact Microscopy (SXCM) of Caenorhabditis elegans nematodes with typical length
m and diameter
m has been performed using the PALS laser source of wavelength
m and pulse duration
ps. Pulsed soft X-rays were generated using molybdenum and gold targets with laser intensities
W/cm2. Images have been recorded on PMMA photo resists and analyzed using an atomic force microscope operating in contact mode. Cuticle features and several internal organs have been identified in the SXCM images including lateral field, cuticle annuli, pharynx, and hypodermal and neuronal cell nuclei.Received: 18 February 2004, Published online: 29 June 2004PACS:
42.62.Be Biological and medical applications - 07.85.Tt X-ray microscopes - 87.59.Bh X-ray radiographyA color version of the figures is available in electronic form at . 相似文献
9.
R. M. Jennerich A. N. Keiser D. A. Tate 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,40(1):81-89
We have obtained Doppler-free spectra of transitions in the
→ 2p2(3P)
and
→
multiplets of atomic nitrogen using saturated absorption spectroscopy. These multiplets consist of
respectively of seven and eight transitions, and have center of gravity wavelengths of 821 nm and 869 nm. Values for the hyperfine
structure coupling constants of all the upper and lower states for these multiplets were obtained for both 14N and 15N. Isotope shifts of three transitions in each multiplet were also measured, and a significant J-dependence to the shifts
was observed. 相似文献
10.
M. Z.M. Kamali K. Ratnavelu Y. Zhou 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(2):267-279
The recent theoretical work by Bartlett et al. [J. Phys. B 38, L95 (2005)] and the latest measurements on the reduced Stokes parameters
,
and
for 54.4 eV electron impact excitation of the 2p state atomic hydrogen by Williams and Mikosza [J. Phys. B 39, 4113 (2006)] has motivated the present work. A coupled-channel-optical calculation with 9 and 12 atomic states supplemented
with the continuum optical potentials for the stronger coupling channels has been performed. The calculated n = 2 and n =
3 differential cross sections and the reduced Stokes parameters are comparable with the state-of-the art calculations. There is closer agreement between the present calculations and the experimental measurements for the reduced
Stokes parameters
and
in the n = 2p excitation at 54.4 eV. The present CCO calculations also display good accord with the limited experimental
data for the reduced Stokes parameters in the n=3p excitation. 相似文献
11.
We discuss the angular distribution of the lepton pair in the Drell-Yan process,
. This process gives information on the spin-density matrix
of the annihilating quark-antiquark pair in
. There is strong experimental evidence that even for unpolarised initial hadrons
is non-trivial, and therefore the quark-antiquark system is polarised. We discuss the possibilities of a general
- which could be entangled - and a factorising
. We argue that instantons may lead to a non-trivial
of the type indicated by experiments.Received: 6 December 2004, Published online: 9 February 2005 相似文献
12.
We report on recent
progress in our Ramsey-Bordé interferometer with cold magnesium
atoms at 457.2 nm. A resolution as high as
was achieved, which corresponds to a quality factor of Q
= 2.3×1012. An upper limit of 170 Hz for the laser
oscillator line width is inferred from the interferometric analysis
of the contrast decay induced by the residual atomic motion and
spontaneous emission. The performance of the spectrometer allows to
realize an optical frequency standard at 457.2 nm with a short-term
stability of up to
with 105 atoms similar to state-of-the art, non-cryogenic microwave
clocks or oscillators. 相似文献
13.
Twist-3 distribution amplitudes of the pion and kaon are studied in this paper. We calculate the first several moments for the twist-3 distribution amplitudes (
and
) of the pion and kaon by applying the QCD sum rules. Our results show that (i) the first three moments of
and the first two moments of
and
of the pion and kaon can be obtained with 30
uncertainty; (ii) the fourth moment of the
and the second moment of the
can be obtained when the uncertainty are relaxed to 35
; (iii) the fourth moment of the
can be obtained only when the uncertainty are relaxed to 40
; (iv) we have
and
after including the
-corrections to the perturbative part. These moments will be helpful for constructing the twist-3 wave functions of the pion and kaon.Received: 6 January 2005, Revised: 29 March 2005, Published online: 22 June 2005PACS:
13.20.He, 11.55.Hx 相似文献
14.
G. Spavieri 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,39(2):157-166
The wave equation for light propagation in slowly moving media, which is
analogous to that of quantum effects of the Aharonov-Bohm type, is
characterized by the interaction momentum
, related to the flow
. In effects of the Aharonov-Bohm type the interaction momentum
is related to the momentum of the electromagnetic (em) fields, that
characterizes an em flow
. It is shown that in both cases
has the same physical origin. Calculation of the interaction em momentum
for the light wave dragged by the flow yields exactly the
Fresnel-Fizeau momentum. These results corroborate the validity of the
magnetic model for light and highlight the role and relevance of the em
momentum in new effects of classical and quantum physics. A tentative test
of an astrophysical Fizeau-Aharonov-Bohm effect is discussed. 相似文献
15.
The production of
, D0, D + , Ds + and
charm hadrons and their antiparticles in e p scattering at HERA was measured with the ZEUS detector using an integrated luminosity of
. The measurement has been performed in the photoproduction regime with the exchanged-photon virtuality
and for photon-proton centre-of-mass energies in the range
. The charm hadrons were reconstructed in the range of transverse momentum
and pseudorapidity
. The production cross sections were used to determine the ratio of neutral and charged D-meson production rates,
, the strangeness-suppression factor,
, and the fraction of charged D mesons produced in a vector state,
. The measured
and
values agree with those obtained in deep inelastic scattering and in e + e- annihilations. The measured
value is smaller than, but consistent with, the previous measurements. The fractions of c quarks hadronising as a particular charm hadron,
, were derived in the given kinematic range. The measured open-charm fragmentation fractions are consistent with previous
results, although the measured
is smaller and
is larger than those obtained in e + e- annihilations. These results generally support the hypothesis that fragmentation proceeds independently of the hard sub-process.
Received: 12 August 2005, Revised: 8 September 2005, Published online: 6 October 2005 相似文献
16.
B. F. Parsons K. E. Strecker D. W. Chandler 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(1):15-20
In our previous work we investigated electronically non-adiabatic effects in
using crossed molecular beam scattering
coupled with velocity mapped ion imaging. The prior experiments placed
limits on the cross-section for electronically non-adiabatic spin-orbit
excitation
and electronically non-adiabatic spin-orbit
quenching
.
In the present work, we investigate
electronically non-adiabatic spin-orbit quenching for
which is the required first step for the
reaction of Cl* to produce ground state HCl+H products. In these
experiments we collide Cl (2P) with H2 at a series of fixed
collision energies using a crossed molecular beam machine with velocity
mapped ion imaging detection. Through an analysis of our ion images, we
determine the fraction of electronically adiabatic scattering in
Cl* +H2, which allows us to place limits on the cross-section for
electronically non-adiabatic scattering or quenching. We determine the following
quenching cross-sections σ quench(2.1 kcal/mol) = 26 ±
21 ?2, σ quench(4.0 kcal/mol) = 21 ±
49 ?2, and σ quench(5.6 kcal/mol) = 14 ±
41 ?2. 相似文献
17.
S. H. Li C. Wang J. S. Liu X. X. Wang R. X. Li G. Q. Ni Z. Z. Xu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2005,34(1-3):215-218
Using time-of-flight spectrometry, the interaction of intense femtosecond
laser pulses with argon clusters has been studied by measuring the energy
and yield of emitted ions. With two different supersonic nozzles, the
dependence of average ion energy
on cluster size
in a large range of
has been measured. The experimental results indicate that
when the cluster size
, the average ion
energy
Coulomb explosion is the
dominant expansion mechanism. Beyond this size, the average ion energy gets
saturated gradually, the clusters exhibit a mixed Coulomb-hydrodynamic
expansion behavior. We also find that with the increasing gas backing
pressure, there is a maximum ion yield, the ion yield decreases as the gas
backing pressure is further increased. 相似文献
18.
M. Beneke Th Feldmann D. Seidel 《The European Physical Journal C - Particles and Fields》2005,41(2):173-188
We provide standard model expectations for the rare radiative decays
,
and
, and the electroweak penguin decays
and
at the next-to-leading order (NLO), extending our previous results to
transitions. We consider branching fractions, isospin asymmetries and direct CP asymmetries. For the electroweak penguin decays, the lepton-invariant mass spectrum and forward-backward asymmetry is also included. Radiative and electroweak penguin transitions in
are mainly interesting in the search for new flavor-changing neutral current interactions, but in addition the
decays provide constraints on the CKM parameters
. The potential impact of these constraints is discussed.Received: 16 January 2005, Published online: 16 March 2005
Corresponding author: Th. Feldmann 相似文献
19.
H. K. Wöhri 《The European Physical Journal C - Particles and Fields》2005,43(1-4):407-413
During the June 2002 run NA60 collected around 600 000 dimuon triggers in proton-nucleus collisions at 400 GeV. We show that
the collected dimuon mass spectra can be understood in terms of known sources. The specific target setup, consisting of Beryllium,
Indium and Lead targets, simultaneously exposed to the beam, allowed us to study the nuclear dependence of the production
cross-section of the
and
resonances. The elementary nucleon-nucleon production cross-sections at 400 GeV for the
,
and
mesons are also presented. By using the
-Dalitz decay, dominating the mass range below 450 MeV, we, furthermore, extracted the
production cross-section and its nuclear dependence. The results are discussed in the framework of previous measurements,
mostly obtained in different decay channels, performed by NA27, HELIOS-1 and CERES-TAPS.
Arrival of the final proofs: 1 July 2005
PACS:
25.75.Dw, 25.75.Nq 相似文献
20.
J. Bielcikova 《The European Physical Journal C - Particles and Fields》2005,43(1-4):323-327
A study of elliptic flow and two-particle azimuthal correlations of charged particles (
GeV/c) and high-
pions (
GeV/c) in Pb + Au collisions at 158A GeV/c, close to midrapidity, is presented. Elliptic flow (v
2) rises linearly with
to a value of about 10
at 2 GeV/c. Beyond
1.5 GeV/c, the slope decreases and possibly indicates a v
2 saturation at high
. Two-pion azimuthal anisotropies for
1.2 GeV/c exceed the v
2 values by about 60
in semicentral collisions. This non-flow component is attributed to near-side and away-side jetlike correlations. While the
near-side peak remains constant with centrality 0.23
0.03 rad, as expected for fragmentation, the away-side peak experiences broadening and disappears in central collisions.
Arrival of the final proofs: 30 June 2005
PACS:
25.75.Ld, 25.75.Gz 相似文献