arXiv subjects

N. Behzadi

Publications and source records attributed to N. Behzadi.

12 recordsLinked to original sources

arXiv2018

Requirement of system-reservoir bound states for entanglement protection

In this work, a genuine mechanism of entanglement protection of a two-qubit system interacting with a dissipative common reservoir is investigated. Based on the generating of bound state for the system-reservoir, we show that stronger bound state in the energy spectrum can be created by adding other non-interacting qubits into the reservoir. In the next step, it is found that obtaining higher degrees of boundedness in the energy spectrum leads to better protection of two-qubit entanglement against the dissipative noises. Also, it is figured out that the formation of bound state not only exclusively determines the long time entanglement protection, irrespective to the Markovian and non-Markovian dynamics, but also performs the task for reservoirs with different spectral densities.

quant-ph↗

arXiv2017

Controlling speedup in open quantum systems through the manipulating of system-reservoir bound states

In this paper, we give a mechanism for controlling speedup of a single-qubit open quantum system by exclusively manipulating the system-reservoir bound states using additional non-interacting qubits. It is demonstrated that providing stronger bound states in the system-reservoir spectrum makes the single-qubit evolution with higher speed. We examine the performance of the mechanism for different spectral densities such as Lorentzian and Ohmic and find out the decisive role of bound states manipulation in speeding up of quantum evolution.

quant-ph↗

arXiv2017

Quantum speed limit time for a two-qubit system interacting with independent and common reservoirs

We study the quantum speed limit time for a two-qubit system interacts with indepen- dent and common reservoir. The system is initially prepared in a class of X-structure density matrix, namely the extended Werner-like states (EWL). We demonstrate that when reservoir enters to the non-Markovian regime, the quantum speed limit time de- crease more sharply in a common reservoir than independent reservoirs.

quant-ph↗

arXiv2017

Quantum discord protection of a two-qutrit V-type atomic system from decoherence by partially collapsing measurements

In this paper, by exploiting the weak measurement and quantum measurement re- versal (WMQMR) procedure, we propose a scheme to show how one can protect the geometric quantum discord (GQD) of a two-qutrit V-type atomic system each of which interacts with a dissipative reservoir independently. We examine the scheme for the GQD of the initial two-qutrit Werner and Horodecki states for different classes of weak mea- surement strengthes. It is found out that the presented protocol enables us to suppress decoherence due to the amplitude damping (AD) channel and preserve the quantum dis- cord of the two-qutrit system successfully.

quant-ph↗

arXiv2016

Effect of two-qutrit entanglement on quantum speed limit time of a bipartite V-type open system

In the present paper, quantum speed limit (QSL) time of a bipartite V-type three-level atomic system under the effect of two-qutrit entanglement is investigated. Each party interacts with own independent reservoir. By considering two local unitarily equivalent Wener states and the Horodecki PPT state, as initial states, the QSL time is evaluated for each of them in the respective entangled regions. It is counterintu-itively observe that the effect of entanglement on the QSL time driven from each of the initial Werner states are completely different when the degree of non-Markovianity is considerable. In addition, it is interesting that the effect of entanglement of the non-equivalent Horodecki state on the calculated QSL time displays an intermediate behavior relative to the cases obtained for the Werner states.

quant-ph↗

arXiv2014

Selective transfer of superposition of coherent states by exploiting a cavity QED system

We propose a scheme on the basis of a N+2 identical single-mode coupled-cavity QED system for selective transfer of a qubit constructed from superposition of standard coherent states. The cavities arranged in such way that the intermediate or channel cavity is connected uniformly to the sender and N receiver cavities. We consider N different ternary sets of identical QDs whose QDs have been distributed in the sender, channel and one of the receiver cavities respectively. We demonstrate a situation in which the dynamics of the system is confined selectively in a sub sector belongs to one of the ternary set of QDs. This selective dynamics is able to transfer the coherent state-constructed qubit (CSCQ) from the sender party to the desired receiver one reliably. Also, we illustrate that the scheme is optimally robust due to dissipations arises from photon losses in the cavities.

quant-ph↗

arXiv2014

Robust construction of entangled coherent GHZ and W states in a cavity QED system

By exploiting a system of three distant cavities, we propose a scheme for constructing tripartite entangled coherent GHZ and W states which are robust due to the photon losses in the cavities. Each of cavities is doped with a semiconductor quantum dot. By the dynamics, the excitonic modes of quantum dots are enabled to exhibit entan-gled coherent GHZ and W states. Apart from the exciton losses, the master equation approach shows that when the populations of the field modes in the cavities are negli-gible the destruction of entanglement due to decoherence arises from photon losses, is effectively suppressed.

quant-ph↗

arXiv2013

Perfect routing of quantum information in regular cavity QED networks

We introduce a scheme for perfect routing of quantum states and entanglement in regular cavity QED networks. The couplings between the cavities are quasi-uniform and each cavity is doped with a two-level atom. Quasi-uniform couplings leads the system to evolve in invariant subspaces. Combination the evolutions of the system in its invariant subspaces with quite simple local operations on atoms in the networks, gives the perfect routing of quantum states and entanglement through the network. To provide the protocol be robust due to decoherence arisen from photon loss, the field mode of the cavities are only virtually excited.

quant-ph↗

arXiv2013

Perfect transfer of coherent state-based qubits via coupled cavities

Motivated by the need for communication of coherent state-based qubits in quantum computers, we introduce a method for perfect transferring of an arbitrary superposition of coherent states between two distant nodes of a linear array of three semiconductor QDs. The QDs trapped in a system of coupled cavities. In this method, the field mode of the cavities, as the resource of transferring of quantum states, are only virtually excited which minimizes the effect of decoherence due to photon loss.

quant-ph↗

arXiv2010

Constructing Entanglement Witness Via Real Skew-Symmetric Operators

In this work, new types of EWs are introduced. They are constructed by using real skew-symmetric operators defined on a single party subsystem of a bipartite dxd system and a maximal entangled state in that system. A canonical form for these witnesses is proposed which is called canonical EW in corresponding to canonical real skew-symmetric operator. Also for each possible partition of the canonical real skew-symmetric operator corresponding EW is obtained. The method used for dxd case is extended to d1xd2 systems. It is shown that there exist Cd2xd1 distinct possibilities to construct EWs for a given d1xd2 Hilbert space. The optimality and nd-optimality problem is studied for each type of EWs. In each step, a large class of quantum PPT states is introduced. It is shown that among them there exist entangled PPT states which are detected by the constructed witnesses. Also the idea of canonical EWs is extended to obtain other EWs with greater PPT entanglement detection power.

quant-ph↗

arXiv2010

Entanglement Witnesses and Characterizing Entanglement Properties of Some PPT States

On the basis of linear programming, new sets of entanglement witnesses (EWs) for 3x3 and 4x4 systems are constructed. In both cases, the constructed EWs correspond to the hyperplanes contacting, without intersecting, the related feasible regions at line segments and restricted planes respectively. Due to the special property of the contacting area between the hyper-planes and the feasible regions, the corresponding hyper-planes can be turned around the contacting area throughout a bounded interval and hence create an infinite number of EWs. As these EWs are able to detect entanglement of some PPT states, they are non-decomposable (nd-EWs).

quant-ph↗

arXiv2008

Two-qutrit Entanglement Witnesses and Gell-Mann Matrices

The Gell-Mann $λ$ matrices for Lie algebra su(3) are the natural basis for the Hilbert space of Hermitian operators acting on the states of a three-level system(qutrit). So the construction of EWs for two-qutrit states by using these matrices may be an interesting problem. In this paper, several two-qutrit EWs are constructed based on the Gell-Mann matrices by using the linear programming (LP) method exactly or approximately. The decomposability and non-decomposability of constructed EWs are also discussed and it is shown that the $λ$-diagonal EWs presented in this paper are all decomposable but there exist non-decomposable ones among $λ$-non-diagonal EWs.

quant-ph↗