共查询到20条相似文献,搜索用时 0 毫秒
1.
This paper proposes a scheme to teleport an arbitrary multi-particle two-level atomic state between two parties or an arbitrary zero- and one-photon entangled state of multi-mode between two high-Q cavities in cavity QED. This scheme is based on the resonant interaction between atom and cavity and does not involve Bell-state measurement. It investigates the fidelity of this scheme and find out the case of this unity fidelity of this teleportation. Considering the practical case of the cavity decay, this paper finds that the condition of the unity fidelity is also valid and obtains the effect of the decay of the cavity on the successful probability of the teleportation. 相似文献
2.
We propose a novel scheme for the efficient production of entangled states for N photons of the form |N>(a)|0>(b) + |0>(a)|N>(b) (NOON states) based on the resonant interaction of a pair of quantized cavity modes with an ensemble of atoms. We show that, in the strong-coupling regime, the adiabatic evolution of the system tends to a limiting state that describes mesoscopic entanglement between photons and atoms which can easily be converted to a purely photonic or atomic NOON state. We also demonstrate the remarkable property that the efficiency of this scheme increases exponentially with the cavity cooperativity factor, which gives efficient access to high number NOON states. The experimental feasibility of the scheme is discussed, and its efficiency is demonstrated numerically. 相似文献
3.
R. Safaiee M. M. Golshan 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,83(4):457-463
The present work is concerned with an analysis of the entanglement between the electronic
coherent superpositions of spin states and subbands in a
quasi-one-dimensional Rashba nanoloop acted upon by a strong perpendicular magnetic field.
We explicitly include the confining potential and the Rashba spin-orbit coupling into the
Hamiltonian and then proceed to calculate the von Neumann entropy, a measure of
entanglement, as a function of time. An analysis of the von Neumann entropy demonstrates
that, as expected, the dynamics of entanglement strongly depends upon the initial state
and electronic subband excitations. When the initial state is a pure one formed by a
subband excitation and the z-component of spin states, the entanglement exhibits periodic
oscillations with local minima (dips). On the other hand, when the initial state is formed
by the subband states and a coherent superposition of spin states, the
entanglement still periodically oscillates, exhibiting stronger correlations, along with
elimination of the dips. Moreover, in the long run, the entanglement for the latter case
undergoes the phenomenon of collapse-revivals. This behaviour is absent for the first case
of the initial states. We also show that the degree of entanglement strongly depends upon
the electronic subband excitations in both cases. 相似文献
4.
本文讨论了在双Λ型原子系统中制备相干叠加态的方法:一个Λ型系统通过控制激光而另一个Λ型系统采用部分受激拉曼绝热通道的方法.在理论上分析了产生任意相干叠加态的可能性并且讨论了透热系统在产生相干叠加态过程中的重要性.研究表明,没有透热过程是不可能制备出任意的叠加态.应用数值方法验证理论分析是正确,并且指出任意叠加态的产生只与控制脉冲的时间延迟有关. 相似文献
5.
Polarization filtering and atomic cell filtering
are applied in the identification of Stokes signals in an atomic
ensemble, and reduce the noise to a level of 10^ - 5 and 10^
- 4 respectively. Good Stokes signals are then obtained. In this
article the two filtering systems and the final Stokes output
are presented, and the optimization of the polarization filtering
system is highlighted. 相似文献
6.
Quantum tunneling of the magnetization in a single molecule magnet has been studied in experiments that combine microwave spectroscopy with high sensitivity magnetic measurements. By monitoring spin-state populations in the presence of microwave radiation, the energy splittings between low lying superpositions of high-spin states of single molecule magnet Ni4 (S=4) have been measured. Absorption linewidths give an upper bound on the rate of decoherence. Pulsed microwave experiments provide a measure of energy relaxation time, which is found to increase with frequency. 相似文献
7.
8.
We propose a protocol to achieve high fidelity quantum state teleportation of a macroscopic atomic ensemble using a pair of quantum-correlated atomic ensembles. We show how to prepare this pair of ensembles using quasiperfect quantum state transfer processes between light and atoms. Our protocol relies on optical joint measurements of the atomic ensemble states and magnetic feedback reconstruction. 相似文献
9.
10.
Schleier-Smith MH Leroux ID Zhang H Van Camp MA Vuletić V 《Physical review letters》2011,107(14):143005
We demonstrate cavity sideband cooling of a single collective motional mode of an atomic ensemble down to a mean phonon occupation number ?n?(min?)=2.0(-0.3)(+0.9). Both ?n?(min) and the observed cooling rate are in good agreement with an optomechanical model. The cooling rate constant is proportional to the total photon scattering rate by the ensemble, demonstrating the cooperative character of the light-emission-induced cooling process. We deduce fundamental limits to cavity cooling either the collective mode or, sympathetically, the single-atom degrees of freedom. 相似文献
11.
We experimentally establish a non-classical correlation between a single Stokes photon and the collective spin excited state of a cold atomic ensemble by using a spontaneous Raman scattering process. The correlation between them can be proved by transferring the spin excited state of the atomic ensemble into an anti-Stokes photon and checking the Cauchy-Schwarz inequality between the Stokes and the anti-Stokes photons. The non-classical correlation can be kept for at least 300 ns. 相似文献
12.
Single photons are generated from an ensemble of cold Cs atoms via the protocol of Duan et al. [Nature (London), ()]]. Conditioned upon an initial detection from field 1 at 852 nm, a photon in field 2 at 894 nm is produced in a controlled fashion from excitation stored within the atomic ensemble. The single-quantum character of field 2 is demonstrated by the violation of a Cauchy-Schwarz inequality, namely w(1(2),1(2)|1(1))=0.24+/-0.05 not > or = 1, where w(1(2),1(2)|1(1)) describes the detection of two events (1(2),1(2)) conditioned upon an initial detection 1(1), with w-->0 for single photons. 相似文献
13.
The frequency spectrum of the fluorescence must be reduced when studying interactions between atoms and parametric fluorescence using the photon counting method since photon counting does not distinguish the light frequency. An interference filter and etalons successfully reduced the frequency spectrum of the parametric fluorescence from 6.6 THz to 1.7 GHz. The parametric fluorescence after frequency filtering showed the non-classical feature violating a Cauchy-Schwartz inequality for the intensity correlation function. We used slow light propagation with Rb gas to demonstrate that the obtained light source interacts with the atoms. 相似文献
14.
We present a detailed analysis of phase sensitivity for a nonlinear Ramsey interferometer, which utilize effective mean-field interaction of a two-component Bose–Einstein condensate in phase accumulation. For large enough particle number N and small phase shift ? , analytical results of the Ramsey signal and the phase sensitivity are derived for a product coherent state | θ , 0 ? . When collisional dephasing is absent, we confirm that the optimal sensitivity scales as 2/N 3/2 for polar angle of the initial state θ = π /4 or 3π /4. The best-sensitivity phase satisfies different transcendental equations, depending upon the initial state and the observable being measured after the phase accumulation. In the presence of the collisional dephasing, we show that the N -3/2-scaling rule of the sensitivity maintains with spin operators J ^ x and J ^ y measurements. A slightly better sensitivity is attainable for optimal coherent state with θ = π /6 or 5π /6. 相似文献
15.
The process of the simultaneous absorption of three photons in a medium possessing weak one-photon absorption is analyzed.
The mode experiencing absorption is perturbed externally via a three-photon parametric process. It is shown that a steady-state,
three-component superposition state of light can exist in this system in the range where the amplitude of the state is small
(small perturbations of the system). The latter condition is due to the fact that, in this range of interactions, the field
spends significantly more time in one of three types of superposition states of light that form an ensemble of quantum trajectories
of the system than in the other two. 相似文献
16.
We consider the formation of entangled quantum states for an atomic Bose condensate interacting with an external electromagnetic field in a single-particle state under conditions of change in various regimes for exchange interaction processes. These states of the Bose system have high phase coherence and are accompanied by the generation of squeezed states of a new type in terms of the parameters defined by a combination of transition operators for the condensate atoms and external-field photons with an appropriate polynomial deformation of the algebra SU(2). We show that localized quantum structures corresponding to stable elementary excitations of the atoms and the field in the condensate can be formed in principle. We also analyze the purely quantum effects of collapse and revival for the level populations of the Bose condensate and the change in atomic statistics as well as determine the conditions for the formation of superstructure of these unsteady states for the Bose system. 相似文献
17.
Wu H George RE Wesenberg JH Mølmer K Schuster DI Schoelkopf RJ Itoh KM Ardavan A Morton JJ Briggs GA 《Physical review letters》2010,105(14):140503
Strong coupling between a microwave photon and electron spins, which could enable a long-lived quantum memory element for superconducting qubits, is possible using a large ensemble of spins. This represents an inefficient use of resources unless multiple photons, or qubits, can be orthogonally stored and retrieved. Here we employ holographic techniques to realize a coherent memory using a pulsed magnetic field gradient and demonstrate the storage and retrieval of up to 100 weak 10?GHz coherent excitations in collective states of an electron spin ensemble. We further show that such collective excitations in the electron spin can then be stored in nuclear spin states, which offer coherence times in excess of seconds. 相似文献
18.
We investigate superradiant cascade emissions from an atomic ensemble driven by two-color classical fields. The correlated pair of photons (signal and idler) is generated by adiabatically driving the system with large-detuned light fields via four-wave mixing. The signal photon from the upper transition of the diamond-type atomic levels is followed by the idler one which can be superradiant due to light-induced dipole–dipole interactions. We then calculate the cooperative Lamb shift (CLS) of the idler photon, which is a cumulative effect of interaction energy. We study its dependence on a cylindrical geometry, a conventional setup in cold atom experiments, and estimate the maximum CLS which can be significant and observable. Manipulating the CLS of cascade emissions enables frequency qubits that provide alternative robust elements in quantum network. 相似文献
19.
S. T. Gevorgyan 《Optics and Spectroscopy》2005,99(1):116-125
The process of simultaneous absorption of two photons in a medium in the presence of a weak one-photon absorption is considered. The medium is perturbed from outside in a two-photon parametric manner. The formation of a stationary even-parity superposition state of light in such a medium is shown to be possible in the region of small amplitudes of the state (weak perturbations of the system). This is associated with the fact that, in this region of interaction, the field spends considerably more time in the even superposition state than in the odd state. It is shown that a nonstationary superposition state of light with a large amplitude of the state (large photon numbers) can be obtained for interaction times that are longer than the most probable time of the first two-photon quantum jump of the field state and shorter than the most probable time of the first one-photon jump of the field state. The dynamics of formation of the quantum entropy of the field is studied by numerical simulation of quantum trajectories of the system. The Wigner functions of the state of the field are calculated. Analytical results are obtained for the density matrix of the stationary state of the system in the presence of a weak one-photon absorption. 相似文献