Physical Review A (24699934)110(3)
A feasibility study is done for the possibility of a universal set of quantum gate implementation based on phononic state via fourth-order Duffing nonlinearity in an optomechanical system. The optomechanical system consists of N doubly clamped coupled nanobeam arrays driven by local static and radio frequency electrical potentials, coupled to a single-mode high-finesse optical cavity. The results show that the ideal cnot gate can be implemented only under nonresonance dynamics when the dissipation processes are negligible. © 2024 American Physical Society.
Scientific Reports (20452322)14(1)
An array of metallic nanoparticles can diffract or concentrate the incident electromagnetic wave and behave as an antenna. In this paper, the effects of the inner sub-wavelength structure of nanoparticles are studied on the directivity of the plasmonic nanoantenna, which is coated on the output of a waveguide. Three 5*5 element configurations are analyzed: nanocubes, nanoshells, and nanoframes array. Numerical results are obtained using the 3D FDTD technique. The results show that structured nanoantennas can improve the antenna's directivity due to the plasmonic properties and hybridization mechanism. Between the three configurations investigated in the 250–800 nm wavelength range, the nanoshell array exhibits maximum and minimum amounts of its directivity at 321.5 nm and 591 nm, respectively. At 558 nm, nanoframes and nanoshells' arrays show the same amount of directivity, and from the wavelength greater than 558 nm, the nanoframe array has the best performance. The results may help design and fabricate directive optical fiber endcaps. © The Author(s) 2024.
Physical Review E (24700045)108(6)
We investigate the effect of localization on the local charging of quantum batteries (QBs) modeled by disordered spin systems. Two distinct schemes based on the transverse-field random Ising model are considered, with Ising couplings defined on a Chimera graph and on a linear chain with up to next-to-nearest-neighbor interactions. By adopting a low-energy demanding charging process driven by local fields only, we obtain that the maximum extractable energy by unitary processes (ergotropy) is highly enhanced in the ergodic phase in comparison with the many-body localization (MBL) scenario. As we turn off the next-to-nearest-neighbor interactions in the Ising chain, we have the onset of the Anderson localization phase. We then show that the Anderson phase exhibits a hybrid behavior, interpolating between large and small ergotropy as the disorder strength is increased. We also consider the splitting of total ergotropy into its coherent and incoherent contributions. This incoherent part implies in a residual ergotropy that is fully robust against dephasing, which is a typical process leading to the self-discharging of the battery in a real setup. Our results are experimentally feasible in scalable systems, such as in superconducting integrated circuits. © 2023 American Physical Society.
Physical Review E (24700045)105(5)
One of the most important devices emerging from quantum technology are quantum batteries. However, self-discharging, the process of charge wasting of quantum batteries due to decoherence phenomenon, limits their performance, measured by the concept of ergotropy and half-life time of the quantum battery. The effects of local field fluctuation, introduced by the disorder term in the Hamiltonian of the system, on the performance of the quantum batteries is investigated in this paper. The results reveal that the disorder term could compensate disruptive effects of the decoherence, i.e., self-discharging, and hence improve the performance of the quantum battery via "incoherent gain of ergotropy"procedure. Adjusting the strength of the disorder parameter to a proper value and choosing a suitable initial state of the quantum battery, the amount of free ergotropy, defined with respect to the free Hamiltonian, could exceed the amount of initial stored ergotropy. In addition harnessing the degree of the disorder parameter could help to enhance the half-life time of the quantum battery. This study opens perspective to further investigation of the performance of quantum batteries that explore disorder and many-body effects. © 2022 American Physical Society.
Journal of the Optical Society of America B: Optical Physics (07403224)39(8)pp. 2194-2199
The spin effect on accumulation of the electron density profile in the presence of an external magnetic field is investigated. In this regard, the two-fluid quantum hydrodynamic model is used to derive the interaction of intense laser light with magnetized quantum plasma. The results emphasize that the initial laser intensity and external magnetic field play significant roles in the accumulation of electron density. Moreover, the behavior of spin-up and spin-down electrons in the same spatial position is completely different. In a way, where spin-up electrons accumulate, spin-down electron density is rarefied. This fact provides a useful recipe for spintronics applications. © 2022 Optica Publishing Group
Physical Review A (24699934)106(6)
Energy can be stored in quantum batteries by electromagnetic fields as chargers. In this paper, the performance of a quantum battery with single and double chargers is studied. It is shown that by using two independent charging fields, prepared in coherent states, the charging power of the quantum battery can be significantly improved, though the average number of embedded photons are kept the same in both scenarios. The results reveal that for the case of initially correlated states of the chargers, the amount of extractable energy, measured by ergotropy, is more than initially uncorrelated ones, with appropriate degrees of field intensity. Though the correlated chargers lead to greater reduction in the purity of the quantum battery, more energy and in turn more ergotropy are stored in this case. In addition, we study the battery-charger mutual information and von Neumann entropy and by using their relation we find that both quantum and classical correlations are generated between the quantum battery and chargers. We also study quantum consonance of the battery as the nonlocal coherence among its cells and find some qualitative relations between the generation of such correlations and the capability of energy storage in the quantum battery. © 2022 American Physical Society.
Journal of the Optical Society of America B: Optical Physics (07403224)38(4)pp. 1200-1204
Quantum teleportation of the quantum correlated states via noisy channels is investigated. The noisy channels are realized by a couple of two-level atoms (qubits) embedded in a zero-temperature bosonic bath. The entanglement of the channels is provided by the interqubit interaction and/or through the memory of the environment. Especially for the case of noninteracting qubits, the resource of the teleportation can be supplied by the entangled state of the channel, which is provided by information backflow in the non-Markovian regime of the evolution. More non-Markovianity of the dynamics generates a higher amount of induced entanglement and hence enhances the quality of the quantum correlation teleportation process. When the degree of non-Markovianity of dynamics is sufficiently high, quantum teleportation, which is superior to classical communication, is achievable. © 2021 Optical Society of America.
Scientific Reports (20452322)11(1)
In this study, the effect of the plasmon hybridization mechanism on the performance and refractive index (RI) sensitivity of nanoshell, nanocage and nanoframe structures is investigated using the finite-difference time-domain simulation. To create nanocage structure, we textured the cubic nanoshell surfaces and examined the impact of its key parameters (such as array of cavities, size of cavities and wall thickness) on the nanocage's RI-sensitivity. Synthesis of the designed nanocages is a challenging process in practice, but here the goal is to understand the physics lied behind it and try to answer the question “Why nanoframes are more sensitive than nanocages?”. Our obtained results show that the RI-sensitivity of nanocage structures increases continuously by decreasing the array of cavities. Transforming the nanocage to the nanoframe structure by reducing the array of cavities to a single cavity significantly increases the RI-sensitivity of the nanostructure. This phenomenon can be related to the simultaneous presence of symmetric and asymmetric plasmon oscillations in the nanocage structure and low restoring force of nanoframe compared to nanocage. As the optimized case shows, the proposed single nanoframe with aspect ratio (wall length/wall thickness) of 12.5 shows RI-sensitivity of 1460 nm/RIU, the sensitivity of which is ~ 5.5 times more than its solid counterpart. © 2021, The Author(s).
Laser Physics Letters (1612202X)17(9)
Remotely preparing quantum states, which possess some desired features, is an important task for future quantum network host providers. On the other hand, the non-degenerate discordant two-qubit states, the states with different left and right quantum discords, is necessary for the implementation of some quantum information and quantum computation processes. This paper presents a new preparation scheme of such states realized by the asymmetric quantum correlation teleportation (AQCT) protocol i.e. quantum correlation teleportation via two different quantum channels. In this way, some properties of AQCT protocol are studied to achieve the most appropriate and least expensive procedure of preparing the asymmetric discordant two-qubit quantum states. © 2020 Astro Ltd.
Physics of Plasmas (1070664X)25(8)
The effects of non-linearity of a medium on the growth rate of filamentation instability in a magnetized plasma interacting with an intense laser pulse is investigated. The non-linearity of the medium, modeled by Kerr non-linearity, is an important factor, which determines the rate of instability growth. The sensitivity of the rate of filamentation growth to the Kerr non-linear coefficient could be adjusted by the external magnetic field and the laser intensity. © 2018 Author(s).
Quantum Information Processing (15700755)16(2)
Dynamics of an open two-qubit system is investigated in the post-Markovian regime, where the environments have a short-term memory. Each qubit is coupled to separate environment which is held in its own temperature. The inter-qubit interaction is modeled by XY–Heisenberg model in the presence of spin–orbit interaction and inhomogeneous magnetic field. The dynamical behavior of entanglement and discord has been considered. The results show that quantum discord is more robust than quantum entanglement, during the evolution. Also the asymmetric feature of quantum discord can be monitored by introducing the asymmetries due to inhomogeneity of magnetic field and temperature difference between the reservoirs. By employing proper parameters of the model, it is possible to maintain nonvanishing quantum correlation at high degree of temperature. The results can provide a useful recipe for studying dynamical behavior of two-qubit systems such as trapped spin electrons in coupled quantum dots. © 2016, Springer Science+Business Media New York.
Quantum Information Processing (15700755)15(4)pp. 1585-1599
A bipartite state is classical with respect to party A if and only if party A can perform nondisruptive local state identification (NDLID) by a projective measurement. Motivated by this we introduce a class of quantum correlation measures for an arbitrary bipartite state. The measures utilize the general Schatten p-norm to quantify the amount of departure from the necessary and sufficient condition of classicality of correlations provided by the concept of NDLID. We show that for the case of Hilbert–Schmidt norm, i.e., (Formula presented.) , a closed formula is available for an arbitrary bipartite state. The reliability of the proposed measures is checked from the information-theoretic perspective. Also, the monotonicity behavior of these measures under LOCC is exemplified. The results reveal that for the general pure bipartite states these measures have an upper bound which is an entanglement monotone in its own right. This enables us to introduce a new measure of entanglement, for a general bipartite state, by convex roof construction. Some examples and comparison with other quantum correlation measures are also provided. © 2015, Springer Science+Business Media New York.
Physical Review A (24699934)94(5)
Due to the axioms of quantum mechanics, perfect cloning of an unknown quantum state is impossible. But since imperfect cloning is still possible, a question arises: "Is there an optimal quantum cloning machine?" Buzek and Hillery answered this question and constructed their famous B-H quantum cloning machine. The B-H machine clones the state of an arbitrary single qubit in an optimal manner and hence it is universal. Generalizing this machine for a two-qubit system is straightforward, but during this procedure, except for product states, this machine loses its universality and becomes a state-dependent cloning machine. In this paper, we propose some classes of optimal universal local quantum state cloners for a particular class of two-qubit systems, more precisely, for a class of states with known Schmidt basis. We then extend our machine to the case that the Schmidt basis of the input state is deviated from the local computational basis of the machine. We show that more local quantum coherence existing in the input state corresponds to less fidelity between the input and output states. Also we present two classes of a state-dependent local quantum copying machine. Furthermore, we investigate local broadcasting of two aspects of quantum correlations, i.e., quantum entanglement and quantum discord, defined, respectively, within the entanglement-separability paradigm and from an information-theoretic perspective. The results show that although quantum correlation is, in general, very fragile during the broadcasting procedure, quantum discord is broadcasted more robustly than quantum entanglement. © 2016 American Physical Society.
Quantum Information Processing (15700755)14(1)pp. 247-267
A general state of an (formula presented) system is a classical-quantum state if and only if its associated (formula presented)-correlation matrix (a matrix constructed from the coherence vector of the party (formula presented), the correlation matrix of the state, and a function of the local coherence vector of the subsystem (formula presented)), has rank no larger than (formula presented). Using the general Schatten (formula presented)-norms, we quantify quantum correlation by measuring any violation of this condition. The required minimization can be carried out for the general (formula presented)-norms and any function of the local coherence vector of the unmeasured subsystem, leading to a class of computable quantities which can be used to capture the quantumness of correlations due to the subsystem (formula presented). We introduce two special members of these quantifiers: The first one coincides with the tight lower bound on the geometric measure of discord, so that such lower bound fully captures the quantum correlation of a bipartite system. Accordingly, a vanishing tight lower bound on the geometric discord is a necessary and sufficient condition for a state to be zero-discord. The second quantifier has the property that it is invariant under a local and reversible operation performed on the unmeasured subsystem, so that it can be regarded as a computable well-defined measure of the quantum correlations. The approach presented in this paper provides a way to circumvent the problem with the geometric discord. We provide some examples to exemplify this measure. © 2014, Springer Science+Business Media New York.
European Physical Journal D (14346060)69(1)
In this paper, the dynamical behaviour of the geometric discord of a system consisting of a two-level atom interacting with a quantised radiation field described by the Jaynes-Cummings model has been studied. The evolution of the system has been considered in the pure dephasing regime when the field is initially in a general pure state and the atom is initially in a mixed state. Dynamics of the geometric discord, as a measure of non-classical correlation, has been compared with the dynamics of negativity, as a measure of quantum entanglement. In particular, the influence of different parameters of system such as detuning and mixedness of the initial atomic state on the dynamics of geometric discord has been evaluated for when the field is initially in coherent and number states. It is shown that for asymptotically large times, the steady state geometric discord of the system presents a non-zero optimum value at some intermediate value of detuning. © EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2015.
International Journal of Theoretical Physics (15729575)54(1)pp. 72-84
Calculation of the quantum discord requires to find the minimum of the quantum conditional entropy (Formula presented.) (Formula presented.) over all measurements on the subsystem B. In this paper, we provide a simple relation for the conditional entropy as the difference of two Shannon entropies. The relation is suitable for calculation of the quantum discord in the sense that it can be used to obtain the quantum discord for some classes of two-qubit states such as Bell-diagonal states and a three-parameter subclass of X states, without the need for minimization. We also present an analytical procedure of optimization and obtain conditions under which the quantum conditional entropy of a general two-qubit state is stationary. The presented relation is also used to find a tight upper bound on the quantum discord. © 2014, Springer Science+Business Media New York.
European Physical Journal D (14346060)63(3)pp. 473-482
The role of spin-orbit interaction arises from the Dzyaloshinskii-Moriya anisotropic antisymmetric interaction on the entanglement transfer via an antiferromagnetic XXZ Heisenberg chain is investigated. From symmetrical point of view the XXZ Hamiltonian with Dzyaloshinskii-Moriya interaction can be replaced by a modified XXZ Hamiltonian which is defined by a new exchange coupling constant and rotated Pauli operators. The modified coupling constant and the angle of rotations depend on the strength of Dzyaloshinskii-Moriya interaction. In this paper we study the dynamical behavior of the entanglement propagation through a system which is consist of a pair of maximally entangled spins coupled to one end of the chain. The calculations are performed for the ground state and the thermal state of the chain separately. In both cases the presence of this anisotropic interaction make our channel more efficient. We show for large values of the strength of this interaction a large family of XXZ chains becomes efficient quantum channels for whole values of anisotropy parameter in the region -2 ≤ Δ ≥ 2. © 2011 EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg.
European Physical Journal D (14346060)62(3)pp. 439-447
We study the entanglement dynamics of an anisotropic two-qubit Heisenberg XYZ system in the presence of intrinsic decoherence. The usefulness of such a system for performance of the quantum teleportation protocol T0 and entanglement teleportation protocol T1 is also investigated. The results depend on the initial conditions and the parameters of the system. The roles of system parameters such as the inhomogeneity of the magnetic field b and the spin-orbit interaction parameter D, in entanglement dynamics and fidelity of teleportation, are studied for both product and maximally entangled initial states of the resource. We show that for the product and maximally entangled initial states, increasing D amplifies the effects of dephasing and hence decreases the asymptotic entanglement and fidelity of the teleportation. For a product initial state and specific interval of the magnetic field B, the asymptotic entanglement and hence the fidelity of teleportation can be improved by increasing B. The XY and XYZ Heisenberg systems provide a minimal resource entanglement, required for realizing efficient teleportation. Also, in the absence of the magnetic field, the degree of entanglement is preserved for the maximally entangled initial states |ψ(0)〉 = 1/ √2(|00〉±|11〉). The same is true for the maximally entangled initial states |ψ(0)〉 = 1/ √2(|01〉±|10〉), in the absence of spin-orbit interaction D and the inhomogeneity parameter b. Therefore, it is possible to perform quantum teleportation protocol T0 and entanglement teleportation T 1, with perfect quality, by choosing a proper set of parameters and employing one of these maximally entangled robust states as the initial state of the resource. © EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2011.
European Physical Journal D (14346060)57(1)pp. 129-140
Entanglement dynamics of an open two-qubit anisotropic XY Heisenberg system is investigated in the presence of an inhomogeneous magnetic field and spin-orbit interaction. We suppose that each qubit interacts with a separate thermal reservoir which is held in its own temperature. The asymptotical and the dynamical behavior of entanglement are analyzed. To distinguish between entanglement induced by the environment and entanglement due to the presence of inter-qubit interaction, the effects of spin-orbit parameter D and temperature difference parameter ΔT on the entanglement of the system have been investigated. We show that for a fixed set of the system parameters, entanglement can be produced just by adjusting the temperature difference between the reservoirs. The size of this entanglement, which is induced by temperature difference of reservoirs, increases as the spin-orbit parameter D increases. Also we find that, this environment induced entanglement can be improved if the qubit influenced by the weaker magnetic field is in contact with the hotter reservoir, i.e. indirect geometry of connection. In this case, the amount of asymptotic entanglement increases as D increases. Regardless of the geometry of connection, increasing D causes the appearance of entanglement in the larger regions of TM-ΔT plane, therefore entanglement can exist in higher temperatures and temperature differences. Furthermore, increasing D enhances the amount of entanglement in these regions. We also show that the state of the system can be found in the maximally entangled state for the case of zero temperature reservoirs and large amount of the spin-orbit parameter. © 2010 EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg.
Physical Review A - Atomic, Molecular, and Optical Physics (10502947)77(4)
The role of spin-orbit interaction in the ground state and thermal entanglement of a Heisenberg XYZ two-qubit system in the presence of an inhomogeneous magnetic field is investigated. We show that the ground state entanglement tends to vanish suddenly for a certain value of the spin-orbit parameter D and, when D crosses its critical value Dc, the entanglement undergoes a revival. Indeed, when D crosses its critical value (Dc), the ground state entanglement tends to its maximum value (C=1). Also, at finite temperatures there are revival regions in the D-T plane. In these regions, entanglement first increases with increasing temperature and then decreases and ultimately vanishes for temperatures above a critical value. We find that this critical temperature is an increasing function of D and that the amount of entanglement in the revival region depends on the spin-orbit parameter. Therefore when spin-orbit interaction is included larger thermal entanglement can exist at higher temperatures. We also show that the rate of enhancement of thermal entanglement by D is not the same for ferromagnetic (Jz <0) and antiferromagnatic (Jz >0) chains. The entanglement teleportation via the quantum channel constructed by the above system is also investigated, and the influence of the spin-orbit interaction on the fidelity of teleportation and entanglement of replica states is studied. We show that, by introducing spin-orbit interaction, the entanglement of the replica state and fidelity of teleportation can be increased for the case of Jz <0. We also argue that a minimal entanglement of the channel is required to realize efficient entanglement teleportation and, in the case of Jz <0, this minimal entanglement can be achieved by introducing spin-orbit interaction. © 2008 The American Physical Society.
