Odd Coherent States Research Articles

Transfer of nonclassical correlations between bosonic field and atomic ensemble through electromagnetically induced transparency

Dark state polariton, as an important concept in the mechanism of electromagnetic induced transparency (EIT), can map the state of bosonic fields to atomic ensembles. To reflect the mapping ability of dark state polariton, we choose the odd and even bosonic coherent states as the probe field in EIT process, and employ spin squeezing, entanglement, and quantum correlation to characterize nonclassical correlations of atomic ensembles during the manipulation of the driving field. It is shown that the differences between the odd and even coherent states are comprehensively reflected in the three characterizations of nonclassical correlations generated through dark state polaritons. The even bosonic coherent states can perfectly transfer bosonic squeezing into atomic ensembles, resulting in spin squeezing. Although the odd bosonic coherent states cannot induce the spin squeezing, they have an advantage over the even bosonic coherent states in generating quantum entanglement and quantum correlations. Furthermore, we demonstrate that atomic ensembles can achieve significant spin squeezing with squeezing degree ∝ 1/N 2/3 through the one-axis twisting (OAT) model and two-axis twisting (TAT) model under the large N limit with the low excitation conditions, and the EIT mechanism was used to transfer the generated spin squeezing to the bosonic field, providing a feasible strategy for obtaining significant bosonic squeezing.

Properties of new even and odd nonlinear coherent states with different parameters

We construct a class of nonlinear coherent states (NLCSs) by introducing a more general nonlinear function and study their nonclassical properties, specifically the second-order correlation function [Formula: see text], Mandel parameter Q, squeezing, amplitude-squared squeezing and Wigner function of the optical field. The results indicate that the nonclassical properties of the new types of even and odd NLCSs crucially depend on the nonlinear functions. More concretely, we find that the new even NLCSs could exhibit the photon-bunching effect, whereas the new odd NLCSs could show the photon-antibunching effect. The degree of squeezing is also significantly affected by the parameter selection of these NLCSs. By employing various forms of nonlinear functions, it becomes possible to construct the NLCSs with diverse properties, thereby providing a theoretical foundation for the corresponding experimental investigations.

Bidirectional quantum teleportation of even and odd coherent states through the multipartite Glauber coherent state: theory and implementation

Bidirectional quantum teleportation of even and odd coherent states through the multipartite Glauber coherent state: theory and implementation

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.

Improving the probabilistic quantum teleportation efficiency of arbitrary superposed coherent state using multipartite even and odd j-spin coherent states as resource

Quantum teleportation is one of the most important techniques for quantum information secure transmission. Using preshared entanglement, quantum teleportation is designed as a basic key in many quantum information tasks and features prominently in quantum technologies, especially in quantum communication. In this work, we provide a new probabilistic teleportation scheme for arbitrary superposed coherent states by employing the multipartite even and odd j-spin coherent states as the entangled resource connecting Alice (sender) and Bob (receiver). Here, Alice possesses both even and odd spin coherent states and makes repeated GHZ states measurements (GHZSMs) on the pair of spins, consisting of (1) the unknown spin state and (2) one of the two coherent spin states, taken alternately, until reaching a quantum teleportation with maximal average fidelity. We provide the relationship between the entanglement amount of the shared state, quantified by the concurrence, with the teleportation fidelity and the success probability of the teleported target state up to the $$n\textrm{th}$$ repeated attempt. In this scheme, we show that the perfect quantum teleportation can be done even with a non-maximally entangled state. Furthermore, this repeated GHZSMs attempt process significantly increases both the average fidelity of the teleported state and the probability of a successful run of the probabilistic protocol. Also on our results, we show that the j-spin number, the target state parameter and the overlap between coherent states provide important additional control parameters that can be adjusted to maximize the teleportation efficiency.

Implementation of Photonic Phase Gate and Squeezed States via a Two-Level Atom and Bimodal Cavity

We propose a theoretical model for realizing a photonic two-qubit phase gate in cavity QED using a one-step process. The fidelity and probability of success of the conditional quantum phase gate is very high in the presence of cavity decay. Our scheme only employs one two-level atom, and thus is much simpler than other schemes involving multi-level atoms. This proposal can also be applied to generate two-mode squeezed states; therefore, we give three examples, i.e., the two-mode squeezed vacuum state, two-mode squeezed odd coherent state, and two-mode squeezed even coherent state, to estimate the variance of Duan’s criterion when taking into account cavity decay. It is shown that the variance is smaller than 2 for the three squeezed states in most cases. Furthermore, we utilize logarithmic negativity to measure the entanglement, and find that these squeezed states have very high degrees of entanglement.

Nonadiabatic geometric quantum computation with cat-state qubits via invariant-based reverse engineering

We propose a protocol to realize nonadiabatic geometric quantum computation of small-amplitude Schr\"odinger cat qubits via invariant-based reverse engineering. We consider a system with a two-photon driven Kerr nonlinearity, which provides a pair of dressed even and odd coherent states, i.e., Schr\"odinger cat states for fault-tolerant quantum computations. An additional coherent field is applied to linearly drive a cavity mode, to induce oscillations between dressed cat states. By designing this linear drive with invariant-based reverse engineering, nonadiabatic geometric quantum computation with cat qubits can be implemented. The performance of the protocol is estimated by taking into account the influence of systematic errors, additive white Gaussian noise, and decoherence including photon loss and dephasing. Numerical results demonstrate that our protocol is robust against these negative factors. Therefore, this protocol may provide a feasible method for nonadiabatic geometric quantum computation in bosonic systems.

High success standard quantum teleportation using entangled coherent state and two-level atoms in cavities

We propose here a new idea for quantum teleportation of superposed coherent state which circumvents the problem of performing non-unitary \(Z_c=|\alpha \rangle \langle \alpha |-|-\alpha \rangle \langle -\alpha |\) operation on coherent state qubit. The receiver only requires to perform either no unitary operation or a \(\pi \) phase shift in order to recreate the information state. We use entangled resource \(\sim |\alpha ,\frac{\alpha }{\sqrt{2}}\rangle -|-\alpha ,-\frac{\alpha }{\sqrt{2}}\rangle \) in contrast with the usual \(\sim |\alpha ,\alpha \rangle -|-\alpha ,-\alpha \rangle \) -(both states unnormalized). Bob receives state which is then superposition of the states \(|\pm \frac{\alpha }{\sqrt{2}}\rangle \). Bob mixes these with even or odd coherent states involving superposition of states \(|\pm \frac{\alpha }{\sqrt{2}}\rangle \) to obtain a two-mode state which is one of \(\sim |I,0\rangle \pm |0,I\rangle \), \(|I\rangle \) being the information state. Bob then obtains the teleported information by using the interaction of one of these modes in two cavities with resonant two-level atoms. This scheme results in average fidelity of \(\simeq 0.95\) for \(|\alpha |^2 \simeq 10\), which increases with \(|\alpha |^2\) and tends to 1 asymptotically, varying as \(1-\frac{\pi ^2}{16|\alpha |^2}+\frac{\pi ^2(\pi ^2+8)}{256|\alpha |^4}\) for large values of \(|\alpha |^2\).

Q-Deformed Coherent States for q-Deformed Photon by Using the Tsallis’s q-Deformed Exponential Function in the Non-Extensive Thermodynamics

In this manuscript we consider q-deformed boson algebra by using the Tsallis’s q-deformed exponential which arises in the non-extensive thermodynamics. Using this we construct q-deformed coherent states and even and odd q-deformed coherent states. We investigate non-classical properties of these q-deformed coherent states such as photon distribution, super-/sub-Poissonian structure and bunching or anti-bunching effect.

Round robin differential quadrature phase shift quantum key distribution by using odd coherent states

In this paper, we propose a round robin differential quadrature phase shift quantum key distribution by using one decoy state and odd coherent states (RRDQPS-QKD-OCS). By comparing existing RRDPS-QKD and RRDQPS-QKD, our proposed protocol, RRDQPS-QKD-OCS, has an outstanding performance, where not only the key generation rate is much larger but also the maximum transmission distance is much longer. Additionally, a one decoy state method is sufficient for RRDQPS-QKD-OCS to be close to the asymptotic limit performance with RRDQPS-QKD-OCS by using infinite decoy states.

Entanglement of formation and quantum discord in multipartite j-spin coherent states

We study the entanglement of formation and the quantum discord contained in even and odd multipartite [Formula: see text]-spin coherent states. The key element of this investigation is the fact that a single [Formula: see text]-spin coherent state is viewed as comprising [Formula: see text] qubit states. We compute the quantum correlations present in the n even and odd [Formula: see text]-spin coherent states by considering all possible bipartite splits of the multipartite system. We discuss the different bi-partition schemes of quantum systems and we examine in detail the conservation rules governing the distribution of quantum correlations between the different qubits of the multipartite system. Finally, we derive the explicit expressions of quantum correlations present in even and odd spin coherent states decomposed in four spin sub-systems. We also analyze the properties of monogamy and we show in particular that the entanglement of the formation and the quantum discord obey the relation of monogamy only for even multipartite [Formula: see text]-spin coherent states.

Even and Odd Coherent States of Wigner Algebra

In this paper the even and odd coherent states for the Wigner algebra is investigated. Some non-classical properties of the even and odd coherent states for the Wigner algebra is also investigated. Indeed, photon number probability distribution, super-/sub-Poissonian structure and squeezing condition are discussed for even and odd coherent states.

Enhancing phase sensitivity with number state filtered coherent states

Number state filtered coherent states are a class of nonclassical states obtained by removing one or more number states from a coherent state. Phase sensitivity of an interferometer is enhanced if these nonclassical states are used as input states. The optimal phase sensitivity, which is related to the quantum Cramer-Rao bound (QCRB) for the input state, improves beyond the standard quantum limit. It is argued that removal of more than one suitable number state leads to better phase sensitivity. As an important limiting case in this context, the even and odd coherent states, where the odd and even number states are filtered from coherent state respectively, are considered. The optimal phase sensitivity for these limiting cases equals that of the squeezed vacuum. It is observed that the improvement in phase sensitivity is not in direct proportion to the nonclassicality of the input states.

Teleporting quantum Fisher information for even and odd coherent states

We present a scheme for implementing a quantum teleportation process using the Jaynes–Cummings model. For this, we study the interaction between an excited state of a two-level atom and a single electromagnetic field in a superposition of coherent states. The resulting entangled state may be considered as a good quantum channel for quantum teleportation protocol. By controlling the interaction field parameters inside the cavity, the average fidelity of the teleported state may be maximized. However, the weight and phase parameters in the teleported states are estimated by using quantum Fisher information. It allows one to show that the sensitivity of the teleported states fluctuates between maximum and minimum bounds for large numbers of photons. Evaluating different quantities of quantum entanglement, average fidelity, and the amount of quantum Fisher information shows that the odd coherent states are usually larger than those obtained using even coherent states.

Dynamic of quantum Fisher information and quantum interferometric power in multipartite coherent states

We examine the role of quantum correlations, contained multipartite Glauber coherent states, in enhancing the precision in the estimation of an unknown phase shift. We give the explicit form of quantum Fisher information in even and odd multipartite coherent states. Two different pairing schemes are considered to evaluate the sensitivity of the probe state to the phase shift for some relevant local Hamiltonians. Also, a particular interest is dedicated to the derivation of the quantum interferometric power which quantifies the amount of non-classical correlations. This quantum correlations quantifier is compared with the original quantum discord built upon von Neumann entropy and we discuss the effects of quantum correlations in quantum metrology protocols. In addition, the dynamics of quantum Fisher information about a dephasing channel is studied. In order to illustrate our results, we examine the situation involving tripartite coherent states to determine the sensitivity of the probe state when the first qubit is driven by an arbitrary local Hamiltonian.

Generalized pair coherent states and non-classical properties

In this paper we generalize the even and odd coherent states into the generalized pair coherent states where two coherent variables have phase difference $ \theta$ . We investigate the non-classical properties for the generalized pair coherent states.

Decoy state quantum-key-distribution by using odd coherent states without monitoring signal disturbance

Recently, a novel quantum-key-distribution (QKD) protocol, called Round-robin-differential-phase-shift (RRDPS) QKD, has been proposed to share a secure key without monitoring the signal disturbance. In this paper, we propose a decoy state RRDPS-QKD protocol with odd coherent states (OCS). We implement a one-intensity decoy state method into the RRDPS-QKD with OCS to estimate the key rate. The results show that both the maximum transmission distance and the key rate of our protocol are significantly improved. Moreover, only one-intensity decoy state is sufficient for the protocol to approach the asymptotic limit with infinite decoy states.

Higher-Order Nonclassical Properties of a Shifted Symmetric Cat State and a One-Dimensional Continuous Superposition of Coherent States

Role of quantum interference in the origin of higher-order nonclassical characteristics of radiation field has been probed vis-a-vis a discrete and a continuous superposition of coherent states. Specifically, the possibilities of observing higher-order nonclassical properties (e.g., higher-order antibunching (HOA), higher-order sub-Poissonian photon statistics (HOSPS), higher-order squeezing (HOS) of Hong-Mandel type and Hillery type) have been investigated using a shifted symmetric cat state that reduces to Yurke-Stoler, even and odd coherent states at various limits. This shifted symmetric cat state which can be viewed as a discrete superposition of coherent states is found to show HOA and HOSPS. Similarly, higher-order nonclassical properties of a one-dimensional continuous superposition of coherent states is also studied here. The investigation has revealed the existence of HOS and HOSPS in the one-dimensional continuous superposition of coherent states studied here. Effect of non-Gaussianity inducing operations (e.g., photon addition and addition followed by subtraction) on these superposition states have also been investigated. Finally, some comparisons have been made between the higher-order nonclassical properties of discrete and continuous superposition of coherent states.

Superposition of single-mode para-Bose coherent states: Generation and nonclassical properties

In this paper, we introduce two classes of superposed states generated by a superposition of two single-mode para-Bose coherent states (CS) with arbitrary relative phase factors. The first class is superposition of two opposite para-Bose CS and second class consists of two para-Bose CS, [Formula: see text] out of phase with each other. These states are reduced to the well-known superposed single-mode CS of the simple harmonic oscillator when the deformation parameter tends to one. We study the nonclassical properties of the introduced states by evaluating their para-Bose Fock state distribution, second-order squeezing, Klyshko’s and Mandel’s parameters. We investigate the essential role of coherent and deformation parameters on their nonclassicality. We show that some nonclassical properties of these states are different from those of the even and odd coherent states. Finally, we present a simple scheme for the physical generation of the introduced states.

Continuous‐Variable Quantum Key Distribution Scheme with Odd Coherent States

The Quantum key distribution (QKD) has been entering the practical application era. The odd coherent state which follows sub Poisson distributed has been confirmed to extend transmission distance and improve secret key rate in Discrete-variable quantum key distribution (DVQKD) protocol. We propose Entanglement-based (EB) scheme of Continuous-variable quantum key distribution (CVQKD) with odd coherent state. This scheme allows distributing Gaussian modulated CVQKD with laser light which could be odd coherent state. We analyze the logarithmic negativity between entangled odd coherent states and the security. The results show that renewed scheme can extend secure distance by 10.6% and enhance the tolerance excess noise in same parameter, and the renewed scheme could be applied to prepare-and-measure (P&M) model in CVQKD.