共查询到20条相似文献,搜索用时 15 毫秒
1.
The evolution of a two-level system subjected to stimulated transitions which is undergoing a sequence of measurements of
the level occupation probability is evaluated. Its time correlation function is compared to the one obtained through the pure
Schr?dinger evolution. Systems of this kind have been recently proposed for testing the quantum mechanical predictions against
those of macrorealistic theories, by means of temporal Bell inequalities. The classical requirement of noninvasivity, needed
to define correlation functions in the realistic case, finds a quantum counterpart in the quantum nondemolition condition.
The consequences on the observability of quantum mechanically predicted violations to temporal Bell inequalities are drawn
and compared to the already dealt case of the rf-SQUID dynamics.
Received: 28 March 1996 / Revised version: 13 August 1996 相似文献
2.
Shi-Biao Zheng 《Optics Communications》2007,278(2):345-349
We propose an efficient scheme for realizing squeezing for a cavity mode. In the scheme, a collection of ladder-type three-level atoms are trapped in a cavity and driven by two classical fields. Under certain conditions, the cavity field deterministically evolves to a squeezed state. The scheme can also be used for conditional generation of superpositions of different squeezed vacuum states. 相似文献
3.
Jesús Urías 《Physics letters. A》2008,372(5):600-603
Locality and fair sampling are proved to be contradictory assumptions in hidden variable models of the Bell test that are based upon a 3-dimensional sample space. This result makes the class of 3-dimensional hidden variable models incompatible with quantum mechanics in the ideal case, independently of detection efficiencies. 相似文献
4.
We analyze the principle of a very general and conceptually simple method for manipulating optical fields by coupling them into a matter waves Young double slit apparatus. The field, non resonant with the atoms, acts as a phase-retarding medium in one of the arms of the interferometer and shifts the atomic fringe pattern. The method constitutes a simple quantum nondemolition measuring scheme of the photon number. Non classical states such as Schrödinger cats and Fock states of the field are generated in the measurement process. The analysis of the atomic interferometer with optical retarding fields provides a very simple and striking illustration of basic concepts of the quantum measurement theory and of the principle of complementarity. This scheme, which would be very difficult to implement in the optical domain, is equivalent to a more feasible and recently proposed Ramsey interference method to measure small microwave fields with beams of Rydberg atoms.Associé au Centre National de la Recherche Scientifique et à l'Université Pierre et Marie Curie 相似文献
5.
G. Brida M. Genovese F. Piacentini 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(3):577-580
Following the theoretical suggestion of [E. Santos, Phys. Lett. A 327, 33 (2004);
E. Santos, Eur. Phys. J. D 42, 501 (2007)], we present experimental results addressed to
test restricted families of local realistic models, but without
relying on the fair sampling assumption. 相似文献
6.
Zavatta et al. [A. Zavatta, S. Viciani, M. Bellini, Science 306 (2004) 660; A. Zavatta, S. Viciani, M. Bellini, Phys. Rev. A 72 (2006) 023820], using parametric down-conversion, have carried out experiments to conditionally generate a single-photon added coherent state. In this Letter, we propose an extension of their method in order to generate the two-photon added coherent state, and point the way toward generating m-photon added coherent states for m>2, all using only one down-conversion crystal. 相似文献
7.
We study optical schemes for generating both a displaced photon and a displaced qubit via conditional measurement. Combining one mode prepared in different microscopic states (one-mode qubit, single photon, vacuum state) and another mode in macroscopic states (coherent state, single photon added coherent state), a conditional state in the other output mode exhibits properties of a superposition of the displaced vacuum and a single photon. We propose to use the displaced qubit and entangled states composed of the displaced photon as components for quantum information processing. Basic states of such a qubit are distinguishable from each other with high fidelity. We show that the qubit reveals both microscopic and macroscopic properties. Entangled displaced states with a coherent phase as an additional degree of freedom are introduced. We show that additional degree of freedom enables to implement complete Bell state measurement of the entangled displaced photon states. 相似文献
8.
We propose a scheme for quantum nondemolition (QND) measurement of the quadrature component of a traveling wave, which uses
the nonlinear ponderomotive interaction of electromagnetic waves reflected from a movable mirror. The influence of mechanical
and optical losses and of imbalance in the interferometer arms is analyzed.
Received: 27 March 1996 / Revised version: 25 September 1996 相似文献
9.
E. Santos 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(3):531-536
A recent experiment by Brida et al. [Eur. Phys. J. D 44, 547 (2007)] is analyzed with the conclusion that the results disagree with standard quantum predictions but fit a simple
local hidden variables model. New experiments are proposed which might throw new light on the anomaly. 相似文献
10.
E. Santos 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(3):501-509
A family of local models containing two angles as hidden variables is
defined for experiments measuring polarization correlation of optical
photons. Searching for the best model of the family, that is giving
predictions most close to quantum mechanics, allows deriving Bell-type
inequalities which may be tested with relatively low detection efficiency. 相似文献
11.
Xun-Li Feng Zhao-Yang Chen Zhi-Zhan Xu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(1):117-121
The nondegenerate two-photon interaction of a two-level atom with a broadband multimode squeezed vacuum is investigated. We
find that in the two-photon process the squeezed vacuum has a driving effect on the atom which can lead to an ac Stark effect
when the average photon number of the squeezed vacuum is larger than a critical value.
Received: 2 February 1999 / Received in final form: 20 April 1999 相似文献
12.
D.G. Angelakis P.L. Knight 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(2):247-250
We show how entangled atomic pairs can be prepared in order to test the Bell inequalities. The scheme is based on the interaction
of the atoms with a highly localized field mode within a photonic crystal. The potential of using optically separated transitions
and the stability of the entangled state to spontaneous emission could lead to the closure of the communication and the detection
loopholes appearing in experiments so far. The robustness of the scheme against detector inefficiencies, the spread in the
atomic velocities and the fact that the entangled pairs are not generated simultaneously is also studied.
Received 31 July 2001 and Received in final form 30 November 2001 相似文献
13.
Numerical and analytical results for the squeezing factor, ζ2, in a pseudo-spin s-1/2 chain. The open chain is composed by N two-level atoms with site-dependent interactions. The time evolution of the squeezing factor is studied, as well as its dependence on the number of atoms and on the interactions. It is found that long-range interactions may optimize the degree of spin squeezing. 相似文献
14.
?ukasz Derkacz 《Physics letters. A》2008,372(48):7117-7123
The dynamics of entanglement between three-level atoms coupled to the common vacuum is investigated. We show that the collective effects such as collective damping, dipole-dipole interaction and the cross coupling between orthogonal dipoles, play a crucial role in the process of creation of entanglement. In particular, the additional cross coupling enhances the production of entanglement. For the specific initial states we find that the effect of delayed sudden birth of entanglement, recently invented by Ficek and Tana? [Ficek, R. Tana?, Phys. Rev. A 77 (2008) 054301] in the case of two-level atoms, can also be observed in the system. When the initial state is entangled, the process of spontaneous emission causes destruction of correlations and its disentanglement. We show that the robustness of initial entanglement against the noise can be changed by local operations performed on the state. 相似文献
15.
K. Zeiske G. Zinner F. Riehle J. Helmcke 《Applied physics. B, Lasers and optics》1995,60(2-3):205-209
Consecutive, phase-coherent, near-resonant optical excitations of atoms have been used to realize an atom interferometer with a beam of thermal calcium atoms. We have measured the topological phase shift due to the interaction of a static electric field with the magnetic dipole moment of a moving atom (Aharonov-Casher effect). The observed phase shift was proportional to the electric field and, within our experimental uncertainty, independent of the particle's velocity. The measured value of the phase shift has been found to agree with the predicted one within a relative uncertainty of 2.2%.Dedicated to H. Walther on the occasion of his 60th birthday 相似文献
16.
Sai-Yun Ye 《Optics Communications》2008,281(5):1306-1311
An approach for realizing conditional phase gate for two atoms separately trapped in two distant cavities mediated by an optical fiber is proposed. Utilizing the adiabatic passage, the atomic spontaneous emission, and the decays of the fiber and cavities are avoided under certain condition. The effects of the losses in the fiber and cavities on the fidelity are analyzed. Moreover, our scheme is not restricted to Lamb-Dicke limit. We also generalize the approach to generate one-dimensional cluster state and entangled state for two collections of atoms. 相似文献
17.
A scheme is presented for generation of entangled states for two atoms trapped in two distant bad cavities. The scheme can work with bad cavities with the coupling strength smaller than the cavity decay rate, which is important from the viewpoint of experiment. In the scheme the atoms have no probability of being populated in the excited state and thus the atomic spontaneous emission is suppressed, which increases the probability of success. The fidelity of the entangled state is not affected by the detection eflciency. Furthermore, the scheme does not require the detection of the left-polarized photon and right-polarized photon at the same time. 相似文献
18.
An exact solution of the problem of two two-level atoms with nondegenerate two-photon transitions and nondegenerate Raman transitions interacting with two-mode radiation field is presented. Asymptotic solutions for system state vectors are obtained in the approximation of large initial coherent fields. The atom-field entanglement is investigated on the basis of the reduced atomic entropy dynamics. The possibility of the system being initially in a pure disentangled state to revive into this state during the evolution process for both models is shown. Conditions and times of disentanglement are derived. 相似文献
19.
E. Majorana P. Puppo P. Rapagnani F. Ricci 《Applied physics. B, Lasers and optics》1997,64(2):145-151
The Back Action Evading technique is a particular kind of quantum non demolition measurement, first proposed by Caves et al.
in 1980 [3]. We present an experimental study to implement the Back Action Evading measurement scheme in monitoring the amplitude
of an harmonic oscillator excited by a classical force. Results showing the agreement of our theoretical model with the experimental
behaviour of our apparatus in the classical regime are presented. We discuss also the optimization of the performance of our
set-up, which should allow to monitor our oscillator in quantum regime even below the standard quantum limit level.
Received: 22 March 1996 相似文献
20.
Based on the technique of integration within an ordered product of operators we investigate a completeness relation of pure states (such as the coordinate eigenstate, the momentum eigenstate and the coherent state) into normally ordered Gaussian forms. The Weyl ordering invariance under similarity transformations is employed to reveal physical meaning of a kind of normally ordered Gaussian operators, which have the similar forms to the bivariate normal distributions in statistics, i.e., the thermo mixed state density matrix. 相似文献