arXiv subjects

Naghi Behzadi

Publications and source records attributed to Naghi Behzadi.

11 recordsLinked to original sources

arXiv2024

Refrigeration by modified Otto cycles and modified swaps through generalized measurements

We introduce two types of thermodynamic refrigeration cycles obtained through modification of the Otto cycle refrigerator by a generalized measurement channel. These refrigerators are corresponding to the activation of the measurement-based stroke before (first type) and after (second type) the full thermalization of the cooling medium by the cold reservoir in the related familiar Otto cycle. We show that the coefficient of performance for the first type modified refrigerator increases linearly in terms of measurement strength parameter, beyond the classical cooling of the known Otto cycle refrigerator. The second type interestingly introduces another autonomous refrigerator whose supplying work is provided by a quantum engine induced by the measurement channel along the modified cycle. By the considered measurement channel, we also establish such modifications on the swap refrigerator. It is observed that the thermodynamic properties of the obtained modified swap refrigerators are the same as of the modified Otto cycle ones respectively.

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arXiv2020

Quantum engine based on general measurements

In this work, we introduce a three-stroke quantum engine with a single-qubit work-ing substance whose cycle consists of two strokes arise due to performing two distinctgeneral quantum measurements and it is completed by thermalization through contactwith a finite temperature thermal reservoir. It is demonstrated that energy is importedinto the engine by first measurement channel and work (usefulenergy) is extracted fromit, in a frictionless isentropic manner, by the second measurement channel. It is par-ticularly shown that the engine is capable to have perfect efficiency. In continuation,we equip the the engine cycle with two additional adiabatic strokes. As illustrated,the presence of adiabatic strokes in the cycle provide an improved lower bound for theparametrized efficiency range of the engine.

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arXiv2018

Protection of entanglement for a two-qutrit V-type open system on the basis of system-reservoir bound states

In this work, a mechanism for long time protection of entanglement of a two-qutrit V-type atomic system each of which interacts independently with a dissipative reservoir is investigated. It is shown that the protection process is related exclusively on the formation of bound states in the system-reservoir energy spectrum. It is demonstrated that the degree of boundedness for the system-reservoir bound states is well-controlled by entering other V-type qutrits into the reservoirs, and also through the manipulation of the spontaneously generated interference related to decay channels of the V-type atoms.

quant-ph↗

arXiv2018

Effects of oscillatory deformations on the coherent and incoherent quantum transport

Inspired by the works of [F. Caruso, New J. Phys. 16, 055015 (2014)] and [T. Scholak et al, J. Phys. B: At. Mol. Opt. Phys. 44 184012 (2011)], which state that for a large class of complex noisy networks, the optimal efficiency of quantum transport is universally obtained by mixing coherent (Hamiltonian) and incoherent (noisy) parts where the contribution of the coherent part is strictly more than incoherent one, we examine the effect of oscillatory deformations on two simple prototypes in order to study their effects on the efficiency of coherent and incoherent energy transport. The prototypes are interchangeable to each other only by a simple phase modulation, such that the dynamics for the first type is only coherent, while for the second one the coherent evolution is completely suppressed and the evolution of the system is only incoherent (noisy). In this regard, it is shown that there exist a special deformation by which the efficiency of incoherent transport becomes better than the coherent one. This result suggests that in the noisy networks with collective harmonic motions, the optimality of transport can be occurred in such a way that the contribution of incoherent term is more than the coherent one.

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arXiv2018

Some properties of Controlled Fusion Frames

Controlled frames in Hilbert spaces have been introduced by Balazs, Antoine and Grybos to improve the numerical output of in relation to algorithms for inverting the frame operator. In this paper we have introduced and displayed some new concepts and results on controlled fusion frames for Hilbert spaces. It is shown that controlled fusion frames as a generalization of fusion frames give a generalized way to obtain numerical advantage in the sense of reconditioning to check the fusion frame condition. For this end, we introduce the notion of Q-duality for Controlled fusion frames. Also, we survey the robustness of Controlled fusion frames under some perturbations.

math.FA↗

arXiv2018

Enhancement of quantum transport efficiency in a noisy spin channel

In this paper, based on the notion of pseudomode framework introduced by Garraway in [Phys. Rev. A 55, 2290 (1997)], we propose a mechanism for enhancing the efficiency of excitation energy transport in a spin channel which is in contact with a Lorentzian reservoir, through the inclusion of other similar auxiliary spin chains into the reservoir. To this aim, a Lindblad-type master equation for the dynamics of the transport process is provided on the basis of pseudomode approach. It is figured out that increasing the number of auxiliary chains in the reservoir enhances the efficiency of transport or equivalently, rises the population of the reaction center attached to the end of the channel. Moreover, it is interesting to note that the mechanism has better efficiency for the channels with longer lengths.

quant-ph↗

arXiv2017

Well-protected quantum state transfer in a dissipative spin chain

In this work, a mechanism for improving the quantum state transfer efficiency in a spin chain, which is in contact with a dissipative structured reservoir, is investigated. The efficiency of the method is based on the addition of similar non-interacting auxiliary chains into the reservoir. In this regard, we obtain the exact solution for the master equation of the spin chain in the presence of dissipation. It is found out that entering more auxiliary chains into the reservoir causes, in general, the better improvement of the fidelity of state transfer along the mentioned chain. Furthermore, it is reveal that the protocol has better efficiency for a chain with longer length. Therefore, by this method, quantum state transfer along a linear chain with an arbitrary number of qubits, can be well-protected against the dissipative noises.

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arXiv2017

Quantum coherence and entanglement preservation in Markovian and non-Markovian dynamics via additional qubits

In this paper, we investigate preservation of quantum coherence of a single-qubit interacting with a zero-temperature thermal reservoir through the addition of noninteracting qubits in the reservoir. Moreover, we extend this scheme to preserve quantum entanglement between two and three distant qubits, each of which interacts with a dissipative reservoir independently. At the long time limit, we obtained analytical expressions for the coherence measure and the concurrence of two and three qubits in terms of the number of additional qubits. It is observed that, by increasing the number of additional qubits in each reservoir, the initial coherence and the respective entanglements are completely protected in both Markovian and non-Markovian regimes. Interestingly, the protection of entanglements occurs even under the individually different behaviors of the reservoirs.

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arXiv2016

Enhancing quantum state transfer efficiency in binary-tree spin networks by partially collapsing measurements

In this work, quantum state transfer (QST) over binary-tree spin networks is studied by using advantages of partially collapsing measurements. To this aim, we perform initially a weak measurement (WM) on central qubit of the binary-tree network, which encoding the state of concern and after time evolution of the whole system, a quantum measurement reversal (QMR) on the destined qubit is performed. By taking the optimal value of the QMR, it is shown that the QST can be improved considerably by controlling the WM strength and by choosing it close enough to 1, near-perfect QST can be achieved. We also show that how entanglement distribution quality over the binary-tree spin network can be obviously improved by using this approach.

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arXiv2016

An improved bound for quantum speed limit time in open quantum systems by introducing an alternative fidelity

In this paper, we introduce a new alternative quantum fidelity for quantum states which perfectly satisfies all Jozsas axioms and is zero for orthogonal states. By employing this fidelity, we derive an improved bound for quantum speed limit time in open quantum systems in which the initial states can be chosen as either pure or mixed. This bound leads to the well-known Mandelstamm-Tamm type bound for nonunitary dynamics in the case of initial pure states. However, in the case of initial mixed states, the bound provided by the introduced fidelity is tighter and sharper than the obtained bounds in the previous works.

quant-ph↗

arXiv2015

Dephasing-assisted selective incoherent quantum transport

Selective energy transport throughout a quantum network connected to more than one reaction center can play an important role in many natural and technological considerations in photo-systems. In this work, we propose a method in which an excitation can be transported from the original site of the network to one of the reaction centers arbitrarily using independent sources of dephasing noises. We demonstrate a situation that in the absence of dephasing noises the coherent evolution of the system has no role in the energy transport in the network. Therefore, incoherent evolution via application of dephasing noises throughout a selected path of the network leads to transfer the excitation completely to a desired reaction center.

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