Superposition Coherent State Research Articles

Phase sensitivity and entanglement of superposition coherent states in Mach–Zehnder interferometer

In this paper, we mainly focus on analyzing the fidelity, parity measurement, phase sensitivity and entanglement properties of the output states corresponding to three quantum superposition coherent states, i.e. even coherent state (ECS), Yurke-Stoler state (YSS) and odd coherent state (OCS). Our results show that the OCS characterizes super-resolution in the phase measurement via parity measurement at the output ports of a Mach–Zehnder interferometer. In addition, we find that the optimal phase sensitivity may approach the Heisenberg limit which is independent of the superposition coefficient of the coherent states. An interesting finding is that the macroscopically entangled coherent states can be experimentally prepared by adjusting the parameters of the nonlinear phase shifter of the MZI.

Quantum properties of superposition opposite coherent states using quantum scissors with conditional measurements

We analyze the quantum properties for the output state of the superposition coherent states with the opposite phase using a quantum scissor. From the perspectives of theoretical calculation and numerical analysis, we discuss the effects of the parameters of the quantum scissors device on different superposition coherent states, such as the probability of successful photon scissor, fidelity, signal gain and squeezing. An interesting finding is that when the input quantum states are even/odd coherent states, signal gain and squeezing for the output quantum state only depend on the amplitude and are independent of the parameters of the quantum scissors. In addition, the quantum properties for other superposition coherent states which are dependent of the amplitude of coherent and the transmittance of beam splitters are also discussed.

Intrinsic decoherence effect on quantum coherence dynamics of a qutrit interacting resonantly with a coherent cavity field

In this paper, we explore the population inversion and entanglement dynamics in a $$\Lambda $$ -qutrit interacting off-resonantly with a coherent cavity field through multi-quanta processes based on the intrinsic decoherence model. Exact solutions of the decoherence model are obtained when the initial cavity field state is considered in two different states, coherent state and even super-position coherent state. The dynamics of the population inversion and the qutrit–cavity negativity are investigated under the effects of the initial cavity states, and the detuning as well as the decoherence. The energy transfer and entanglement induced by the qutrit–cavityinteraction can be controlled by these effects. The qutrit–cavitydetuning and the coherent intensity and the nonclassicality of the initial cavity field play an important role in improving the generated entanglement dynamics.

Dynamical properties of quantum Fisher information of a two-level atoms interacting with two-mode superposition coherent state

A quantum cavity filled with a nonlinear medium (Kerr like medium) and contains a 2-mode field interacting with time dependence of 2-qubit is investigated. Part of the two qubits interact in the form of an amplifier, while the other is in the form of a ladder. The constants of motion are calculated by using the Heisenberg differential equation. Moreover, the analytical solution is calculated by solving the Schrodinger differential equations. Some statistical quantities are calculated to identify the features of the proposed model. The effective of the nonlinear term on the phenomena of collapse and revival are discussed through atomic population. The amount of entanglement between the quantum subsystem, whether it is between the 2-qubit and the cavity field, or between the 2-qubit together are calculated using the linear entropy and the concurrence. The results indicated that there is a superstructure between the atomic population and the linear entropy, concurrence. The intensity of oscillations decreases for the entanglement between the field and the two qubits when the Kerr like medium of the Hamiltonian system is included. The nonclassical distribution of the quantum system decreases after taking Kerr like medium into account.

Two-Qutrit Entangled f-Coherent States

Nonlinear coherent states or f -coherent states are one of the important class of quantum states of light attached to the f -deformed oscillators. They have been introduced in a pioneering work by Manko et al. and have been realized physically as the stationary states of the centre of mass motion of a trapped ion by de Matos Filho et al. To gain insight into the effectiveness of these states in quantum information theory, we introduce qutrit-like states as a result of two-mode superposition coherent states based on two f -coherent states ∣α, f〉 with a specific selection of the nonlinearity function f(n). The control role of the involved parameters, especially the nonlinearity function on the entanglement and statistical properties of the system state is investigated. The generalized I-concurrence measure has been applied to quantify the entanglement of these states and the condition in which quantum entanglement can be enhanced and maximized has been identified. We show that depending on the chosen nonlinearity function, one can observe different nonclassical effects. These trends are also compared with those obtained for the qubit-like superposition of f -coherent states.

Non-locality Correlation in Two Driven Qubits Inside an Open Coherent Cavity: Trace Norm Distance and Maximum Bell Function

We analytically investigate two separated qubits inside an open cavity field. The cavity is initially prepared in a superposition coherent state. The non-locality correlations [including trace norm measurement induced non-locality, maximal Bell-correlation, and concurrence entanglement] of the two qubits are explored. It is shown that, the generated non-locality correlations crucially depend on the decay and the initial coherence intensity of the cavity field. The enhancement of the initial coherence intensity and its superposition leads to increasing the generated non-locality correlations. The phenomena of sudden birth and death entanglement are found.

Entanglement and quantum teleportation via dissipative cavities

A maximum entangled atomic system consists of 2-two level atoms interacts locally with their own dissipative cavity, is discussed. We show that, the amount of the survival entanglement of the atomic system decays as the detuning parameter increases or the coupling constant decreases. A theoretical teleportation is suggest to teleport a state of one cavity initially prepared in a superposition coherent state to the second cavity is discussed, by using the atomic system as a channel. It is shown that, the efficiency of the suggested teleportation may be improved by increasing the detuning parameter or decreasing the coupling constant between the atomic systems and the cavities.

Generation of superposition coherent states of microwave fields via dissipation of a superconducting qubit with broken inversion symmetry

We present an efficient approach for dissipative generation of quantum superposition states in the microwave resonator, which is coupled to a superconducting qubit. We investigate the situation where the inversion symmetry of potential energy of the qubit is broken, and the strong two-photon nonlinear coupling between qubit and resonator can be realized via the transverse and longitudinal couplings. According to the two-photon dissipation and driving process, the dissipation of a qubit can be utilized to steer the microwave field into a quantum superposition of distinct coherent states, i.e., the Schr\odinger cat state. In addition, we also extend the method to produce an entangled coherent state of two spatially separated resonators. Our scheme is based on quantum reservoir engineering and turns detrimental noise into a resource, which makes it feasible in experimental implementation. The present result may have potential applications in the field of quantum information processing with circuit QED systems.

Dynamics of N-configuration four-level atom interacting with one-mode cavity field

In this paper, a model is presented to investigate the interaction between a four-level atom and a single mode of the radiation field. The relative phase, the detuning and the Kerr-like medium are taken into consideration. The exact solution is given when the atom is initially prepared in superposition coherent state. The influences of the relative phase, and the Kerr-like medium on the collapses-revivals, the field entropy and the amplitude-squared squeezing phenomena for the considered system are examined. It is found that these parameters have important effects on the properties of these phenomena.

Two-mode superposition coherent states with spatial vortex structure for the quantized radiation field

Through superposing M two-mode coherent state a two-mode superposition coherent state with a spatial vortex structure in configuration space is constructed. Such quantum vortex state is an eigenstate of sum of squared two-mode annihilation operators and is always entangled. In the limiting condition of large M the quantum vortex state has a modified Bessel–Gaussian vortex structure with topological charge index n. Experimentally, such two-mode vortex states may be prepared by virtue of a multimode coherent state with currently available technology.

Nonclassical features of entangled coherent states

Nonclassical features of entangled coherent states (two-mode superposition coherent states) based on two coherent states shifted in phase by π/2 are discussed. Analysis of Cauchy–Schwartz inequality, two-mode quadrature squeezing, oscillatory and sub-Poissonian photon statistics show that nonclassicality exists for these states. Furthermore, it is also observed that special states have remarkably strong nonclassical properties than the entangled coherent states based on famous even–odd coherent states.

General formalism of the interaction of a single-mode cavity field with a four-level atom

In this paper, we study a general model for an atomic system described by a four-level atom and one mode of the radiation field. The model describes multi-photon processes and includes possible forms of nonlinearities of both the field and the intensity-dependent coupling. The general forms for the constants of motion of the considered atomic system are obtained. We used the Schrodinger equation in solving this problem. The wave function is obtained when the atom is prepared initially in a superposition coherent state. Some of the statistical aspects which are related to this atomic system are calculated. Also, the effect of the Kerr medium on the dynamics of a four-level W -type atom one-mode system are examined.

Generalized Trio Coherent States

Generalized trio coherent states are made by superposing a number of trio coherent states. They possess inherent nonclassical properties such as sub-Poissonian distribution and violation of Cauchy-Schwarz inequalities. Their phase distribution in the framework of the Pegg and Barnett theory is discussed. We study the interaction of the radiation field prepared in a generalized trio coherent state with an atom in a superposition coherent state in the rotating wave approximation. We investigate the time dependence of the sub-Poissonian distribution and the violation of Cauchy-Schwarz inequalities for such a system. General conclusions reached are illustrated by numerical results.

Teleportation of a coherent superposition state via a nonmaximally entangled coherent channel

We investigate the problem of teleportation of a superposition coherent state via a nonmaximally entangled coherent channel. Two strategies are considered to complete the task. The first one uses entanglement concentration to purify the channel to a maximally entangled one. The second one teleports the state through the nonmaximally entangled coherent channel directly. We find that the probabilities of successful teleportation for the two strategies depend on the amplitudes of the coherent states, and the mean fidelity of teleportation using the first strategy is always less than that using the second strategy.

Properties of phase and their evolutions in damped odd and even coherent states

The properties of measured phase operators in damped odd and even coherent states have been studied. The fluctuations associated with measured phase and their squeezing in these states are investigated. The phase properties in damped superposition coherent states are considered too with the help of measured phase operators. These fluctuations and their squeezing are affected by damping and evolve with time elapsing.

Superposition coherent states and their properties

Special kinds of generalized superposition states, superposition coherent states, are studied in this paper. These states can be produced by superposing a pair of coherent states |a〉 and |−a〉. Their quantum statistical properties, the fluctuations of field and squeezing have been discussed in detail. These properties are dependent on superposition phase. We also describe the squeezing regions in phase space for these states.