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In this paper, we derive the work and heat for two kinds of quantum bipartite systems: a closed one and an open one according to the scheme suggested in Ref. (Weimer et al. in EPL 83:30008, 2008). Then the results are used to investigate the evolution of the work and heat in a quantum CNOT gate operations. It is shown that the heat and work conversion cannot be performed in the closed quantum CNOT gate operations. However, the open quantum CNOT gate can be used to perform the conversion of heat and work. If at the beginning, a spin with a large energy-level difference has a greater probability of being in a highly excited state than the other, then the CNOT gate will work as a quantum engine, and if it is initially in highly excited states with a smaller probability than the other, the gate will work as a quantum refrigerator. [ABSTRACT FROM AUTHOR]

Acute alcoholism (AAI) is a common emergency. Currently, there is a lack of preventive and therapeutic drugs with superior safety and efficacy. Curcuma longa, Panax ginseng, Pueraria lobata, Pueraria flower, and Hovenia dulcis Thunb., which are the components of compound turmeric recipe (CTR), are, respectively, used in China as adjuvant therapeutic agents for AAI and alcoholic liver injury, respectively. The purpose of this research was to investigate the effect of traditional compound turmeric recipe in anti-inebriation treatment and to identify its underlying mechanisms. The mice were administered with CTR mixture, and ethanol was subsequently given to mice by gavage. The effects of CTR on the righting reflex, 24-hour survival, drunken behavior, blood ethanol concentration, and pathological changes of liver are depicted. The activities of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) were detected. Besides, the activities of tumor necrosis factor-α (TNF-α), interleukin-8 (IL-8), alcohol dehydrogenase (ADH), aldehyde dehydrogenase (ALDH), cytochrome P450 (P450), superoxide dismutase (SOD), and malondialdehyde (MDA) in the liver and the levels of β-endorphin (β-EP) and leucine enkephalin (LENK) in the brain were also measured. Our results demonstrated that CTR can increase the activities of ADH, ALDH, P450, and SOD and decrease the contents of TNF-α, IL-8, and MDA in the liver. In addition, it can decrease the activities of ALT, AST, and ALP in serum and β-EP and LENK activities in the brain. CTR showed effects on prevention of acute alcoholism, promoting wakefulness, and alleviating alcoholic liver injury, which were likely mediated by the above mechanisms. [ABSTRACT FROM AUTHOR]

Abstract Quantum state transfer is one of the most prominent protocols in quantum information. In the context of optomechanics, it is still an important task, as it allows us to reliably convert an optical pulse into a mechanical excitation. In this paper, the quantum state transfer between a moveable mirror and cavity field is studied when the system is surrounded by non-Markovian environments, which has been recently realized in experiment. Utilizing the experimental spectrum density, we find that the transition from weak non-Markovianity to strong non-Markovianity happens when choosing a suitable optomechanical coupling strength. We also show that quantum state transfer can be implemented with high fidelity in the non-Markovian environment, and the non-Markovian memory effect is helpful for state transfer both in the short-time and long-time scales. [ABSTRACT FROM AUTHOR]

Byusing a hierarchical equations-of-motion approach, we reproducethe two-dimensional electronic spectra of phycoerythrin 545 from RhodomonasCS24 at ambient temperature (294 K). The simulatedspectra are in agreement with the experimental results reported inWong et al. (Nat. Chem. 2012, 4, 396). The evolutions of cross peaks for rephasing spectraand diagonal peaks for nonrephasing spectra have also been plotted.The peaks oscillate with the population times, with frequencies, phases,and amplitudes of the oscillating curves also being qualitativelyconsistent with the experimental results. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, diffusion behavior of Brownian particles moving in a 1D periodic potential landscape has been theoretically investigated by using the general quantum Langevin equation. At first, in the condition of weak disorder, some anomalous diffusive behaviors have been revealed in the process. Then, two types of mean square displacement, ensemble averaged and time averaged mean square displacement, have been investigated in a long time, and the weak ergodicity breaking phenomenon has been revealed. It is shown that the general quantum Langevin equation can exhibit some novel details of the experimental diffusion process. [Copyright &y& Elsevier]

Two-dimensional three-order nonlinear response functions and the laser spectra of the two-level Frenkel-exciton model, interacting with three short laser pulses in direction -k11+k2+k3, are calculated using the numerical path integral. The method is non-Markovian and the results show that the numerical simulation scheme provides a new pathway for theoretically investigating the multidimensional ultrafast laser spectra including the non-Markovian effect [ABSTRACT FROM AUTHOR]

Abstract: In this Letter, the entanglement dynamics of two interacting qubits in a common bath and in two independent baths, at finite and zero temperature are investigated. Entanglement sudden death (ESD) and entanglement sudden birth (ESB) are observed when the two qubits are embedded in two independent baths at finite temperature. At zero temperature, the entanglement of the two qubits may evolve to a steady state with non-zero value when the two qubits are embedded in a common bath, the entanglement sudden birth does not occur when the qubits are embedded in two independent baths. [Copyright &y& Elsevier]

Abstract: Using the numerical path integral method we investigate the decoherence and relaxation of qubits in spin-boson (SB) and spin-intermediate harmonic oscillator (IHO)-bath (SIB) models. The cases that the environment baths with low and medium frequencies are investigated. It is shown that the qubits in SB and SIB models have the same decoherence and relaxation as the baths with low frequencies. However, the qubits in the two models have different decoherence and relaxation as the baths with medium frequencies. The decoherence and relaxation of the qubit in SIB model can be modulated through changing the coupling coefficients of the qubit-IHO and IHO-bath and the oscillation frequency of the IHO. [Copyright &y& Elsevier]

Abstract: In this paper we study the decoherence and purity of a driven solid-state qubit in the Ohmic bath by using the method based on the master equation. At first, instead of solving the master equation we investigate the coefficients of the equation which describe the shift in frequency, diffusive, decoherence, and so on. It is shown that one of the coefficients (we called it decoherence coefficient) is crucial to the decoherence of the qubit in the model. Then we investigate the evolution of the purity of the state in the model. From the analysis of the purity we see that the decoherence time of the qubit decreases with the increase in the amplitude of the driven fields and it increases with the increase in the frequency of the driven fields. [Copyright &y& Elsevier]

Abstract: Using the numerical path integral method we investigate the decoherence and relaxation of qubits coupled to an Ohmic bath directly and via an intermediate harmonic oscillator (IHO). Here, we suppose the oscillation frequencies of the bath modes are higher than the IHO’s. When we choose suitable parameters the qubits in the two models may have almost same decoherence and relaxation times. However, the decoherence and relaxation times of the qubit in the qubit-IHO-bath model can be modulated through changing the coupling coefficients of the qubit-IHO and IHO-bath and the oscillation frequency of the IHO. [Copyright &y& Elsevier]

Abstract: In this paper we investigate decoherence time of superconducting Josephson charge qubit (JCQ). Two kinds of methods, iterative tensor multiplication (ITM) method derived from the quasiadiabatic propagator path integral (QUAPI) and Bloch equations method are used. Using the non-Markovian ITM method we correct the decoherence time predicted by Bloch equations method. By comparing the exact theoretical result with the experimental data we suggest that the Ohmic noise plays the central role to the decoherence of the JCQ. [Copyright &y& Elsevier]

Abstract: In this Letter we investigate an open two-qubit model whose dynamics is not exactly solvable. When the initial state is the maximum entangled state, as the exactly solvable open two-qubit model [D. Tolkunov, V. Privman, P.K. Aravind, Phys. Rev. A 71 (2005) 060308(R)], the decay of entanglement of formation of the model, expressed by concurrence is also governed by the product of suppression factors describing decoherence of the subsystems (qubits). However, if the initial state is not the maximum entangled state, its concurrence will decrease faster than the product of the suppression factors describing decoherence of the qubits. [Copyright &y& Elsevier]

Abstract: In this paper we investigate the short-time decoherence from Ohmic and 1/f noise of single Josephson charge qubit (JCQ). At first, we use the short-time approximation to obtain the dynamics of the open JCQ. Then we calculate the decoherence the measure of which is chosen as the maximum norm of the deviation density operator. It is shown that the decoherence from 1/f noise plays the central role. The total decoherence from Ohmic and 1/f noise is serious at present experiential conditions according to the DiVincenzo criterion. [Copyright &y& Elsevier]

Abstract: In this paper we investigate the short-time decoherence of single Josephson charge qubit (JCQ). The measure of decoherence is chosen as the maximum norm of the deviation density operator. It is shown that when the temperature is low enough (for example, ), within the elementary gate-operation time , the decoherence is smaller than for the present setup of JCQ. Thus, the JCQ is suitable for taking the blocks of quantum computer according to the DiVincenzo low-decoherence criterion. [Copyright &y& Elsevier]

In this paper we calculate the loss of fidelity due to quantum leakage for the Josephson charge qubit (JCQ). In this investigation the characteristic values and characteristic states of the Mathieu equation are used. It is shown that for present typical parameters of JCQ, EJ/Ech ~ 0.02, the loss of the fidelity per elementary operation is about 10-4 which satisfies DiVincenzo's low decoherence criterion. By appropriately improving the designs of the Josephson junction, namely, decreasing EJ/Ech to ~ 0.01, the loss of fidelity per elementary operation can decrease even smaller to 10-5. The first-order nonadiabatic correction is also obtained by using the approach. [ABSTRACT FROM AUTHOR]

Abstract: We study the Fano effect of a closed Aharonov–Bohm mesoscopic interferometer, with a quantum dot embedded in one of the paths, in the presence of dephasing which is introduced by the Büttiker model. An exact analytic formula of conductance including dephasing factor is derived and can be written as an extended Fano form with a complex Fano parameter q. While the total conductance is unitary, the coherent part has broken unitarity due to dephasing, and thus has continuous phase shift. Our results agree with recent experimental measurements. [Copyright &y& Elsevier]

At first, we generally investigate the short-time decoherence of a qubit nonlinearly coupling with a bath. The measure of the decoherence is chosen as the maximum norm of the deviation density operator. Then we concretely investigate the Josephson charge qubit (JCQ) model. It is shown that at the temperature , the loss of fidelity (due to decoherence) of the JCQ is bigger than the DiVincenzo low decoherence criterion. The decoherence will decrease with the decrease of the experimental temperature. When the temperature decreases to the DiVincenzo low decoherence criterion can be satisfied. [Copyright &y& Elsevier]

Abstract: We investigate electron transport and persistent current of a quantum ring weakly attached to current leads. Assuming there is direct coupling (weakly or strongly) between two leads, electrons can transmit by the inter-lead coupling or tunneling through the quantum ring. The interference between the two paths yields asymmetric Fano line shape for conductance. In presence of interior magnetic flux, there is persistent current along the ring with narrow resonance peaks. The positions of the conductance resonances and the persistent current peaks correspond to the quasibound levels of the closed ring. This feature is helpful to determine the energy spectrum of the quantum ring. Our results show that the proposed setup provides a tunable Fano system. [Copyright &y& Elsevier]

In this paper, we investigate the phase shift and absorbed probability of photons in a single atom high Q cavity. It is shown that by adjusting the coupling constant of interaction between atom and cavity field we can obtain a large, stable phase shift with low absorption of photons, which is needed by a qubit for quantum computation. Cavity quantum electrodynamics (QED) and supersymmetry are used in the analysis. [ABSTRACT FROM AUTHOR]

In this paper, we calculate the entanglement-assisted classical capacities of the depolarizing channel, the phase damping channel, the phase flip channel, the bit flip channel, the bit-phase flip channel, the two-Pauli channel and the amplitude channel, and discuss the analytical results obtained. The Stokes parametrization representation of a qubit and the characteristics of unitary covariance of some quantum noisy channels are used in the calculations. [ABSTRACT FROM AUTHOR]

The minimal entanglement fidelities of the phase damping channel, depolarizing channel, two-Pauli channel and amplitude damping channel are calculated. It is shown that for the same condition, the minimal fidelity of the phase damping channel is the biggest among the four channels. The minimal fidelity of the depolarizing channel is bigger than the other two. [ABSTRACT FROM AUTHOR]

A phase state presentation ξ = re[sup iθ]〉 for a two-mode light field is constructed in the context of quantum optics. This phase space formalism is directly connected to phase-related operators. The generalized quasi-probability distribution function Q(ξ) and measurable phase probability distribution function P(θ) are constructed and are useful to obtain information about phase properties of light fields. [ABSTRACT FROM AUTHOR]

In this paper, use is made of supersymmetric transformation to discuss resonance fluorescence of two-level atom driven by a strong laser field and that of three-level atom driven by two single-mode laser fields. The supersymmetric derivation makes the analysis of the physical processes more accurate, clear and efficient. As a result, some new physical processes are revealed by this method. [ABSTRACT FROM AUTHOR]

In this paper, we give a computational approach of work and heat for any quantum systems. We use the strategy that the part of energy exchange with the von Neumann entropy unchanging is defined as work, and the part with the von Neumann entropy changing is defined as heat. We define the work and heat and they are formulated. This method is suitable for the study of any quantum systems (not only bipartite quantum systems, but also single-body, and multi-body quantum systems). As examples, firstly we investigate a bipartite model whose dynamics can be rigorously solved by using the Bloch equation, and secondly, we study two single-body models by using the numerical method of master equation of Redfield form. • Decompose quantum dissipative processes into pure work and pure heat processes. • In a pure heat process the von Neumann entropy is changed, in a pure work process the entropy is unchanged. • In a pure heat processes the eigenvectors remain unchanged, in a pure work process the eigenvalues remain unchanged. [ABSTRACT FROM AUTHOR]

We employ two-dimensional electronic-vibrational (2DEV) spectroscopy to study the coherent dynamics of coupled vibrational modes in an excitonically-coupled dimer model. The advantage of separating excitation and detection in different frequency regimes allows us to directly probe the electronic and vibrational coherences in the time-evolved 2DEV spectra. The complexity of vibrational coherence of two coupled modes is directly revealed by cross peaks in the 2DEV spectra. With the help of the ensuing time traces, we can follow how the vibrational coherence changes over time in the monomer model and, subsequently, in the dimer model. We show that the complexity of two coupled vibrational modes and the interaction between electronic and vibrational coherences in molecular systems can be effectively disentangled using the 2DEV spectroscopy technique. [ABSTRACT FROM AUTHOR]

In this paper, the evolutions of two kinds of witnesses of the non-Markovianity and their rates of changes with time are investigated and compared. Four definitions, the trace distance, fidelity, quantum relative entropy, and quantum Fisher information are used for the first kind of witnesses which are based on the completely positive maps (CPM). Three definitions, the quantum entanglement, quantum mutual information, and quantum discord are used for the second kind of witnesses, and they are based on the local completely positive maps (LCPM). An open two-level quantum system model and a numerically quantum dissipative dynamics method, hierarchy equation of motion (HEM) are used in the investigations. It is shown that the evolutions of the witnesses and their rates of the changes calculated with different definitions clearly show the characteristics of the non-Markovianity and they are in agreement with each other. [ABSTRACT FROM AUTHOR]

In this paper we investigate the decoherence of Josephson charge qubit (JCQ) by using a time-nonlocal (TNL) dynamical method. Three kinds of environmental models, described with Ohmic, super-Ohmic, and sub-Ohmic spectral density functions are considered. It is shown that the TNL method can effectively include the non-Markovian effects in the dynamical solutions. In particular, it is shown that the sub-Ohmic environment has longer correlation time than the Ohmic and super-Ohmic ones. And the Markovian and non-Markovian dynamics are obviously different for the qubit in sub-Ohmic environment. [ABSTRACT FROM AUTHOR]

We investigate the two-dimensional third-order nonlinear electronic spectra using the cumulant expansion (CE) and hierarchical equation of motion (HEM) methods. The HEM method is non-Markovian and nonperturbative. In the CE method, the Markovian approximations are always applied in solving dynamical equations and calculating the line-broadening function. If the Markovian approximation is used in the dynamical solutions and theaffected by the line-broadenin calculations of the line-broadening function in the CE method, the nonlinear electronic spectra obtained are different from those obtained using the HEM method. However, using the non-Markovian line-broadening function, we obtain almost the same spectra from the two methods, even when keeping the Markovian approximation in the dynamical solutions. This may imply that in order to obtain the correct nonlinear electronic spectra, it is crucial to include the non-Markovian effect in the line-broadening function, but it may not matter if the Markovian approximation is used in solving the dynamical equations. [ABSTRACT FROM PUBLISHER]

By solving the master equation of Redfield form, we investigate the decoherence of a reduced open-driven qubit. It is shown that when the driving field has not too large frequency to compare to the Rabi frequency of the qubit system, the decoherence of the qubit is affected by the amplitude but not by the frequency of the driving field. We can prolong the decoherence time of the qubit as we choose an appropriate driving field to operate the qubit. [ABSTRACT FROM AUTHOR]

Abstract: By using the Redfield form of the master equation, we investigate the decoherence times of a double quantum dot charge qubit (DQDCQ) in three different cases, namely when it is coupled to (I) the piezoelectric coupling phonon bath (PCPB), (II) the deformation coupling phonon bath (DCPB), and (III) the Ohmic bath. It is found that our results for cases (I) and (II) are in the same magnitude with those obtained via the exact path integral methods, while for case (III), the decoherence time is in well agreement with the experimental value. [Copyright &y& Elsevier]

In this paper, we propose a novel non-iterative approach based on the two-dimensional discrete wavelet transform (DWT) for generating binary holograms in in-line holography. This method is able to alleviate the degradation appearance on the reconstructed image caused by the direct sign-thresholding. Numerical experiments of this method are given in this paper. It is shown that high-quality images of the binary hologram can be reconstructed by using the proposed method. Additionally, the reconstructed images also contain less amount of noise contamination. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we propose a novel method to detect the best reconstructing distance in phase-shifting digital holography, which can help one to reconstruct high-quality images even though the recording distance is unkonwn. This scheme is based on an algorithm, two-dimensional discrete cosine transform (DCT). Numerical experiments for this method are shown in this paper. It is shown that this method is not only effective but also fast compared to previous schemes for detecting the focal distance in digital holography. Meanwhile, the algorithm can be effective against different types of noise. [Copyright &y& Elsevier]