共查询到20条相似文献,搜索用时 31 毫秒
1.
F. Plastina F. Piperno 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,5(3):411-415
We propose a simple method to obtain a superposition of coherent states on a circle, including Schr?dinger cat states as a
special case, via conditional measurement of the state of three level atoms interacting with a one mode cavity field. In the low amplitude
limit, very good approximation of Fock states can also be generated in this way.
Received: 8 October 1998 / Accepted: 30 October 1998 相似文献
2.
H.-y. Fan A. Wünsche 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,15(3):405-412
We examine the existence of right-hand eigenstates (or eigenkets) of the boson creation operator a
and determine their coordinate and their Bargmann representation. The eigenkets of the creation operator are ultrasingular
and cannot be considered as a limiting case of normalizable states. Applications of these eigenstates as auxiliary states
for purposes of representation of states by path integrals over coherent states are discussed. A completeness relation for
coherent states on paths through the complex plane is derived and special examples of its application are considered.
Received 9 March 2001 and Received in final form 13 June 2001 相似文献
3.
X.-M. Hu J.-S. Peng 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,5(2):291-299
On the basis of the nondegenerate quantum-beat laser model, we introduce a coherent field which drives the transition between the upper lasing level and an
auxiliary level. We demonstrate that such a four-level system can produce squeezed two-mode laser without and with inversion.
When the laser is operated well above threshold, the intensity fluctuation in the average mode is reduced below the shot noise
with an optimum Mandel parameter Q=- 1/2. At the same time, the noises in the relative amplitude and the relative phase drop to their vaccum noise levels. Furthermore,
regardless of inversion, noninversion, and transition between inversion and noninversion, the optimum Mandel Q parameter of Q=- 1/2 is retained when the system operates well above threshold. A simple physical explanation of the squeezing mechanism
for two-mode squeezing is given.
Received: 22 December 1997 / Revised: 25 March 1998 / Accepted: 9 September 1998 相似文献
4.
X.-G. Wang S.-H. Pan G.-Z. Yang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,10(3):415-422
We study the nonclassical properties and algebraic characteristics of the negative binomial states introduced by Barnett recently.
The ladder operator formalism and displacement operator formalism of the negative binomial states are found and the algebra
involved turns out to be the SU(1,1) Lie algebra via the generalized Holstein-Primarkoff realization. These states are essentially Perelomov's SU(1,1) coherent states. We reveal their connection with the geometric states and find that they are excited geometric states.
As intermediate states, they interpolate between the number states and geometric states. We also point out that they can be
recognized as the nonlinear coherent states. Their nonclassical properties, such as sub-Poissonian distribution and squeezing
effect are discussed. The quasiprobability distributions in phase space, namely the Q and Wigner functions, are studied in detail. We also propose two methods of generation of the negative binomial states. d
32.80.Pj Optical cooling of atoms; trapping
Received 8 May 1999 and Received in final form 8 November 1999 相似文献
5.
M. Dakna L. Knöll D.-G. Welsch 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,3(3):295-308
State preparation via conditional output measurement on a beam splitter is studied, assuming the signal mode is mixed with a mode prepared in a
Fock state and photon numbers are measured in one of the output channels. It is shown that the mode in the other output channel
is prepared in either a photon-subtracted or a photon-added Jacobi polynomial state, depending upon the difference between
the number of photons in the input Fock state and the number of photons in the output Fock state onto which it is projected.
The properties of the conditional output states are studied for coherent and squeezed input states, and the probabilities
of generating the states are calculated. Relations to other states, such as near-photon-number states and squeezed-state-excitations,
are given and proposals are made for generating them by combining the scheme with others. Finally, effects of realistic photocounting
and Fock-state preparation are discussed.
Received: 17 March 1998 / Revised and Accepted: 8 May 1998 相似文献
6.
A. R. Usha Devi R. Prabhu M. S. Uma 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,40(1):133-138
Production and analysis of non-Gaussian radiation fields has evinced a lot of attention recently.
Simplest way of generating such non-Gaussians is through adding (subtracting) photons to
Gaussian fields.
Interestingly, when photons are added to classical Gaussian fields, the resulting states exhibit
non-classicality.
Two important classical Gaussian radiation fields are coherent and thermal states. Here, we
study the non-classical features of
such states when photons are added to them. Non-classicality of these states shows up in the
negativity of the
Wigner function. We also work out the entanglement potential, a recently proposed measure
of non-classicality for these states. Our analysis reveals that photon added coherent states are
non-classical for all seed beam intensities; their non-classicality increases with the addition
of more number of photons. Thermal state exhibits non-classicality at all temperatures, when a
photon is added; lower the temperature, higher is their non-classicality. 相似文献
7.
Z.-C. Wang Z.-Y. Chen Y. Xu 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(2):185-190
A theoretical study is made of the steady-state populations of a three-level atom in a ladder configuration, driven by a superposition
of a monochromatic laser wave with a broad-band squeezed vacuum. The master equation for the system and the atomic Bloch equations
are derived. The steady-state populations are calculated numerically and shown graphically as functions of two-photon detuning
for various cases of the squeezed vacuum. It is shown that, the atomic populations depend strongly on the relative phase of
the driving field and the squeezed vacuum. When the phase matching condition is fulfilled, there will be a strong two-photon
resonant absorption from the squeezed vacuum, a characteristic different from absorption of photons from a classical field.
Received: 28 May 1997 / Revised and Accepted: 10 December 1997 相似文献
8.
A. Messina 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(3):379-383
A new conditional scheme for generating Bell states of two spatially separated high-Q cavities is reported. Our method is based on the passage of one atom only through the two cavities. A distinctive feature
of our treatment is that it incorporates from the very beginning the unavoidable presence of fluctuations in the atom-cavity
interaction times. The possibility of successfully implementing our proposal against cavity losses and atomic spontaneous
decay is carefully discussed.
Received 31 July 2001 and Received in final form 9 October 2001 相似文献
9.
L. Vernac M. Pinard V. Josse E. Giacobino 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(1):129-135
Using a quantum theory for an ensemble of two- or three-level atoms driven by electromagnetic fields in an optical cavity,
we show that the various spins associated with the atomic ensemble can be squeezed. Two kinds of squeezing are obtained: on
the one hand self-spin squeezing when the input fields are coherent ones and the atomic ensemble exhibits a large non-linearity;
on the other hand squeezing transfer when one of the incoming fields is squeezed.
Received 14 August 2001 and Received in final form 7 November 2001 相似文献
10.
E. Santos 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(3):423-431
Several examples of photon entanglement are studied in the Q representation of quantum optics. In particular, the entangled states produced in parametric downconversion are studied in
detail, and we determine the conditions for the violation of Bell's inequality. Our approach shows that photon entanglement
is related to the existence of correlations between the quantum fluctuations of the electromagnetic field associated to different
modes.
Received 10 August 2002 / Received in final form 7 November 2002 Published online 4 February 2003 相似文献
11.
Transmission resonances in magnetic-barrier structures 总被引:1,自引:0,他引:1
Y. Guo Z.-Q. Li B.-L. Gu Q. Sun J.-Z. Yu Y. Kawazoe 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(2):263-270
Quantum transport properties of electrons in simple magnetic-barrier (MB) structures and in finite MB superlattices are investigated
in detail. It is shown that there exists a transition of transmission resonances, i.e., from incomplete transmission resonances in simple MB structures consisting of unidentical blocks, to complete transmission
resonances in comparatively complex MB structures (, n is the number of barriers). In simple unidentical block arrangements in double- and triple-MB structures we can also obtain
complete transmission by properly adjusting parameters of the building blocks according to ky-value (ky is the wave vector in y direction). Strong suppression of the transmission and of the conductance is found in MB superlattices which are periodic
arrangements of two different blocks. The resonance splitting effect in finite MB superlattices is examined. It is confirmed
that the rule (i.e., for n-barrier tunneling the splitting would be (n-1)-fold) obtained in periodic electric superlattices can be extended to periodically arranged MB superlattices of identical
blocks through which electrons with tunnel, and it is no longer proper for electrons with k
y
<0 to tunnel.
Received: 18 August 1997 / Revised: 20 September 1997 / Accepted: 13 October 1997 相似文献
12.
A.-S. F. Obada G. M. Abd Al-Kader 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(1):189-198
The nonlinear extensions of the single-mode squeezed vacuum and
squeezed coherent states are studied. We have constructed the
nonlinear squeezed states (NLSS's) realization of
SU(1,1) Lie algebra. Two cases of this realization are
considered for unitary and non-unitary deformation operator
function. The nonlinear squeezed coherent states (NLSCS's)
are defined and special cases of these states are obtained.
Some nonclassical properties of these states are discussed. The
s-parameterized characteristic function and various moments are
calculated. The Glauber second-order coherence function is
calculated. The squeezing properties of the NLSCS's are studied.
Analytical and numerical results for the quadrature component
distributions for the NLSCS's are presented. A generation scheme for
NLSCS's using the trapped ions centre-of-mass motion approach is
proposed. 相似文献
13.
G.M. Abd Al-Kader 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(3):429-438
The s-parameterized characteristic function for the output field with the superposition of squeezed displaced Fock states (SDFS's)
as input field is given. The s-ordered distribution functions for the output field with superposition of SDFS's as input state are investigated. Various
moments are calculated by using the s-ordered characteristic function for that field. The Glauber second-order coherence function is calculated. The quadrature
squeezing for the output field are discussed. Some Quasiprobability distribution functions of the output fields are plotted
as functions of the interaction time. The quadrature squeezing for the output field are discussed.
Received 30 September 1998 相似文献
14.
A class of finite-dimensional even and odd pair coherent states, which may be generated via the vibrational motion of a trapped ion in two-dimensional harmonic potential in experiment, is constructed and then some of its statistical properties are discussed. The study shows that the new states exhibit remarkably different statistical properties for different parameters q and ξ. 相似文献
15.
K.-H. Song W.-J. Zhang G.-C. Guo 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(2):267-269
A scheme for preparing entangled coherent states is presented. It is based on the atom-cavity-mode Raman interaction. We also
generalize this method for generating multi-mode entangled coherent states. Finally, our experimental feasibility is discussed.
Received 15 September 2001 and Received in final form 15 November 2001 相似文献
16.
Shi-Biao Zheng 《Czechoslovak Journal of Physics》2002,52(3):379-385
A scheme is proposed for generating two-mode SU(2) and SU(1,1) cat states for an ion trapped in a two-dimensional (2D) anisotropic
harmonic potential trap. In the scheme the ion is excited by two laser beams in the trap plane. After an interaction time,
a measurement on the internal state collapses the ion motion onto a superposition of two SU(2) or SU(1,1) coherent states
depending on the laser frequencies.
This work was supported by the National Natural Science Foundation of China under Grant No. 60008003, Fujian Provincial Natural
Science Foundation of China under Grant Nos. K20004 and F0110027, and Funds from Fuzhou University. 相似文献
17.
R. Migliore A. Messina A. Napoli 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(3):585-588
We prove that a mesoscopic Josephson junction, irradiated with a quantum superposition of two -out of phase optical coherent states, exhibits an experimentally observable sensitivity to the quantum coherences of the
field state.
Received 1 June 1999 and Received in final form 30 July 1999 相似文献
18.
F. C. Lourenço A. Vidiella-Barranco 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(1):127-131
We propose a scheme in which entanglement can be transferred from atoms (discrete variables) to
entangled states of cavity fields (continuous variables). The cavities play the role of a kind of quantum memory for
entanglement, in such a way that it is possible to retrieve it back to the atoms. In our method, two
three level atoms in a lambda configuration, previously entangled, are set to interact with
single mode cavity fields prepared in coherent states. During the process, one e-bit of entanglement may be
deposited in the cavities in an efficient way. We also show that the stored entanglement may be transferred back
to flying atoms. 相似文献
19.
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
20.
Faisal A.A. El-Orany J. Peřina V. Peřinová M. Sebawe Abdalla 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(1):141-156
The evolution of the Schr?dinger-cat states in a dissipative parametric amplifier is examined. The main tool in the analysis
is the normally ordered characteristic function. Squeezing, photon-number distribution and reduced factorial moments are discussed
for the single- and compound-mode cases. Also the single-mode Wigner function is demonstrated. In addition to the decoherence
resulting from the interaction with the environment (damped case) there are two sources which can cause such decoherence in
the system even if it is completely isolated: these are the decay of the pump and the relative phases of the initial cat states.
Furthermore, for the damped case there are two regimes, which are underdamped and overdamped. In the first (second) regime
the signal mode or the idler mode “collapses" to a statistical mixture (thermal field).
Received 25 September 2001 / Received in final form 30 May 2002 Published online 13 December 2002
RID="a"
ID="a"e-mail: sebaweh@awalnet.net.sa
RID="b"
ID="b"Joint Laboratory of Optics of Palacky University and Institute of Physics, Academy of Sciences of the Czech Republic,
17. listopadu 50, 772 07 Olomouc, Czech Republic. 相似文献