共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
M. Feng 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(3):371-377
The Raman interaction of a ultracold ion trapped with two travelling wave lasers is studied analytically with series solutions,
in the absence of the rotating wave approximation (RWA) and without restrictions of both the Lamb-Dicke limit and the weak
excitation regime. The comparison is made between our solutions and those obtained under the RWA in order to demonstrate the
validity region of the RWA. As a practical example, the preparation of Schr?dinger-cat states is proposed beyond the weak
excitation regime, using our calculations.
Received 12 March 2001 and Received in final form 16 October 2001 相似文献
3.
T. Aichele A.I. Lvovsky S. Schiller 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(2):237-245
A detailed theoretical analysis of the spatiotemporal mode of a single photon prepared via conditional measurements on a photon pair generated in the process of parametric down-conversion is presented. The maximum
efficiency of coupling the photon into a transform-limited classical optical mode is calculated and ways for its optimization
are determined. An experimentally feasible technique of generating the optimally matching classical mode is proposed. The
theory is applied to a recent experiment on pulsed homodyne tomography of the single-photon Fock state [A.I. Lvovsky et al., Phys. Rev. Lett. 87, 050402 (2001)].
Received 16 July 2001 相似文献
4.
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
5.
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
6.
Shi-Biao Zheng Guang-Can Guo 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,1(1):105-107
We propose a method for preparing superpositions of coherent states of the motion of an ion in an anisotropic two-dimensional
trap, in which the ion is tightly bound in the y direction. In the scheme the ion is excited by two resonant laser beams with equal amplitude, propagating along the x and y directions, respectively. In the Dicke-Lamb limit, an initial coherent state of the ion motion can be converted into a superposition
of several coherent states on a circle through the laser-ion interactions and state-selective measurements on the ion.
Received: 30 May 1997 / Revised: 29 July 1997 / Accepted: 22 October 1997 相似文献
7.
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
8.
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
9.
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
10.
N. Korolkova Ch. Silberhorn O. Glöckl S. Lorenz Ch. Marquardt G. Leuchs 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(2):229-235
We present schemes for the generation and evaluation of continuous variable entanglement of bright optical beams and give
a brief overview of a variety of optical techniques and quantum communication applications on this basis. A new entanglement-based
quantum interferometry scheme with bright beams is suggested. The performance of the presented schemes is independent of the
relative interference phase which is advantageous for quantum communication applications.
Received 1st August 2001 相似文献
11.
A. Bramati J.-P. Hermier V. Jost E. Giacobino 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(3):421-427
The combined effects of the pump noise suppression and injection locking technique on the intensity noise of a diode pumped
Nd:YVO4 microchip laser are theoretically and experimentally investigated. Complete cancellation of the relaxation oscillation peak
is experimentally achieved. Very good agreement between experimental results and theoretical predictions of a fully quantum
model describing lasers with injected signal is found.
Received 10 December 2001 and Received in final form 6 March 2002 相似文献
12.
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
13.
L. Vernac M. Pinard E. Giacobino 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,17(1):125-136
We show the equivalence between an ensemble of two-level atoms driven by a squeezed vacuum field, and a harmonic oscillator
coupled to a squeezed field. We give the conditions for optimal squeezing transfer from the field to the atomic ensemble.
We show that EPR-type correlations are created between the atomic ensemble and the incoming field.
Received 23 January 2001 相似文献
14.
Preparation of Fock states and quantum entanglement via stimulated Raman adiabatic passage using a four-level atom 总被引:3,自引:0,他引:3
S.-Q. Gong R. Unanyan K. Bergmann 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,19(2):257-262
We study the behaviour of an atom-cavity system exposed to a stimulated Raman adiabatic passage (STIRAP) process in a four-level
system, with a coupling scheme which generate two degenerate dark states. We find that the non-adiabatic interaction of the
two dark states guarantees that the cavity Fock states can always be generated by both intuitively and counterintuitively
ordered pulses. Furthermore, we propose a method to entangle two atoms. Depending on the ordering of the pulses two orthogonal
entangled states can be prepared. Since these entangled states do not have component of the excited states included, the technique
is robust against the detrimental consequences of spontaneous emission.
Received 20 March 2001 相似文献
15.
Room temperature stable single-photon source 总被引:2,自引:0,他引:2
A. Beveratos S. Kühn R. Brouri T. Gacoin J.-P. Poizat P. Grangier 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(2):191-196
We report on the realization of a stable solid state room temperature source for single photons. It is based on the fluorescence
of a single nitrogen-vacancy (NV) color center in a diamond nanocrystal. Antibunching has been observed in the fluorescence
light under both continuous and pulsed excitation. Our source delivers 2×104 s-1 single-photon pulses at an excitation repetition rate of 10 MHz. The number of two-photon pulses is reduced by a factor of
five compared to strongly attenuated coherent sources.
Received 1st August 2001 and Received in final form 2 October 2001 相似文献
16.
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
17.
M. Pelton C. Santori G.S. Solomon O. Benson Y. Yamamoto 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(2):179-190
Current quantum cryptography systems are limited by the attenuated coherent pulses they use as light sources: a security loophole
is opened up by the possibility of multiple-photon pulses. By replacing the source with a single-photon emitter, transmission
rates of secure information can be improved. We have investigated the use of single self-assembled InAs/GaAs quantum dots
as such single-photon sources, and have seen a tenfold reduction in the multi-photon probability as compared to Poissonian
pulses. An extension of our experiment should also allow for the generation of triggered, polarization-entangled photon pairs.
The utility of these light sources is currently limited by the low efficiency with which photons are collected. However, by
fabricating an optical microcavity containing a single quantum dot, the spontaneous emission rate into a single mode can be
enhanced. Using this method, we have seen 78% coupling of single-dot radiation into a single cavity resonance. The enhanced
spontaneous decay should also allow for higher photon pulse rates, up to about 3 GHz.
Received 8 July 2001 and Received in final form 25 August 2001 相似文献
18.
M. Sebawe Abdalla F.A.A. El-Orany J. Peřina 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,13(3):423-438
In the present paper we introduce a new squeeze operator, which is related to the time-dependent evolution operator for Hamiltonian
representing mutual interaction between three different modes. Squeezing phenomenon as well as the variances of the photon-number
sum and difference are considered. Moreover, Glauber second-order correlation function is discussed, besides the quasiprobability
distribution function and phase distribution for different states. The joint photon-number distribution is also reported.
Received 29 March 2000 and Received in final form 20 September 2000 相似文献
19.
R. Folman J. Schmiedmayer H. Ritsch D. Vitali 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,13(1):93-107
Following almost a century of debate on possible “independent of measurement" elements of reality, or “induced" elements of
reality - originally invoked as an ad-hoc collapse postulate, we propose a novel line of interference experiments which may be able to examine the regime of induced
elements of reality. At the basis of the proposed experiment, lies the hypothesis that models of “induced" elements of reality
should exhibit symmetry breaking within quantum evolution. The described symmetry experiment is thus aimed at being able to detect and resolve spatial symmetry breaking signatures. The proposed experiment stands at
the edge of present day technological abilities and will be, so we believe, realizable in the near future.
Received 2 December 1999 and Received in final form 6 April 2000 相似文献
20.
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