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We investigate the Fano line shape in electron transport through a quantum dot in presence of dephasing. The dephasing effect is introduced by the Büttiker model. We derive a generalized Fano formula for the conductance that includes the components of the standard Fano line shape and the Breit–Wigner line shape. According to this formula the Fano parameter |q| decreases when the dephasing strength increases by increasing the temperature. The increase of the half width of the resonance peak by increasing the temperature measured by Zacharia et al. [Phys. Rev.B64, 155311 (2001)] which is more rapid than expected from the ordinary theories is possibly attributed to the dephasing.

We analyze theoretically a hybridization type dressing of orbital (i.e., charge) and spin degrees of freedom of excitations captured in semiconductor quantum dot with band phonons and magnons (the latter for magnetic semiconductor surroundings), as a mechanism of dephasing of rapidly excited dot exciton state. Within the Green function approach we derive our previously formulated heuristic general rule for estimation of corresponding dephasing time-rate. The pure dephasing (off-diagonal decoherence) of quantum dot exciton resulting due to this dressing is studied, for both orbital and spin states of the exciton. A significant difference between phonon-induced (for charge) and magnon-assisted (for spin) quantum dot exciton dephasing is indicated as the result of the spin conservation, which leads to the disappearance of the exciton spin pure-dephasing at T = 0 (freezing out of spin dephasing), in contrary to the exciton charge dephasing caused by phonons, which maintains strong even at T = 0.

In this paper, we investigate the Lindblad dynamics arising due to single particle loss and local dephasing in a d-dimensional nonrelativistic quantum system. Using Schwinger–Keldysh functional techniques, we derive the static mean field equation for the symmetry broken phase. Fluctuations over mean field are studied within the Bogoliubov approximation, and the momentum distribution and effective temperature are calculated. An effective temperature arises which depends on the dephasing rate $\mathrm{\Gamma }$ and mean field particle density. Furthermore, a perturbative renormalization group (RG) upto one loop order is used to study the underlying dynamics of the model. The conditions for the system to be perturbative are obtained.

Experimental studies of the transitions from a primary quantum Hall (QH) liquid at filling factor ν=1/k (with k an odd integer) to the insulator have indicated a "quantized Hall insulator" (QHI) behavior: while the longitudinal resistivity diverges with decreasing temperature and current bias, the Hall resistivity remains quantized at the value kh/e². We review the experimental results and the theoretical studies addressing this phenomenon. In particular, we discuss a theoretical approach which employs a model of the insulator as a random network of weakly coupled puddles of QH liquid at fixed ν. This model is proved to exhibit a robust quantization of the Hall resistivity, provided the electron transport on the network is incoherent. Subsequent theoretical studies have focused on the controversy whether the assumption of incoherence is necessary. The emergent conclusion is that in the quantum coherent transport regime, quantum interference destroys the QHI as a consequence of localization. Once the localization length becomes much shorter than the dephasing length, the Hall resistivity diverges. We conclude by mentioning some recent experimental observations and open questions.

Quantum information protocols are often designed in the ideal situation with no decoherence. However, in real setup, these protocols are subject to the decoherence and thus reducing fidelity of the measurement outcome. In this work, we analyze the effect of state-dependent bath on the quantum correlations and the fidelity of a single qubit teleportation. We model our system-bath interaction as qubits interacting with a common bath of bosons, and the state dependence of the bath is generated through a projective measurement on the joint state in thermal equilibrium. The analytic expressions for the time evolution of entanglement, discord and average fidelity of quantum teleportation are calculated. It is shown that due to the presence of initial system-bath correlations, the system maintains quantum correlations for long times. Furthermore, due to the presence of finite long-time entanglement of the quantum channel, the average fidelity is shown to be higher than its classical value.

Effect of the magnetic field on the rate of phase breaking is studied. It is shown that the magnetic field resulting in the decrease of phase relaxation rate makes the negative magnetoresistance due to suppression of the electron interference to be smoother in shape and lower in magnitude than that found with constant -value. Nevertheless our analysis shows that experimental magnetoconductance curves can be well fitted by the Hikami–Larkin–Nagaoka expression.¹ The fitting procedure gives the value of τ/τ_ϕ, where τ is the quasi-momentum relaxation time, which is close to the value of τ/τ_ϕ(B = 0) with an accuracy of 25% or better when the temperature varies within the range from 0.4 to 10 K. The value of the prefactor α found from this procedure lies within the interval 0.9–1.2.

The mechanism of hole charge transfer in DNA of various lengths and sequences is investigated based on a partially coherent tunneling theory (Zhang et al., J Chem Phys117:4578, 2002), where the effects of phase-breaking in adenine–thymine and guanine–cytosine base pairs are treated on equal foot. This work aims at providing a self-consistent microscopic interpretation for rate experiments on various DNA systems. We will also clarify the condition under which the simple superexchange-mediated-hopping picture is valid, and make some comments on the further development of present theory.

We study decoherence of a three-qubit array coupled to substrate phonons. Assuming an initial three-qubit entangled state that would be decoherence-free for identical qubit positions, allows us to focus on non-Markovian effects of the inevitable spatial qubit separation. It turns out that the coherence is most affected when the qubits are regularly spaced. Moreover, we find that up to a constant scaling factor, two-qubit entanglement is not influenced by the presence of the third qubit, even though all qubits interact via the phonon field.

We address the dynamics of a qubit interacting with a quasi static random classical field having both a longitudinal and a transverse component and described by a Gaussian stochastic process. In particular, we analyze in detail the conditions under which the dynamics may be effectively approximated by a unitary operation or a pure dephasing without relaxation.

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We report our recent numerical study on the effects of dephasing on a perfectly conducting channel (PCC), its presence believed to be dominant in the transport characteristics of a zigzag graphene nanoribbons (GNR) and of a metallic carbon nanotubes (CNT). Our data confirms an earlier prediction that a PCC in GNR exhibits a peculiar robustness against dephasing, in contrast to that of the CNT. By studying the behavior of the conductance as a function of the system's length we show that dephasing destroys the PCC in CNT, whereas it stabilizes the PCC in GNR. Such opposing responses of the PCC against dephasing stem from a different nature of the PCC in these systems.

Recent study in [C. C. Lin, Y. F. Gao, A. V. Penumatcha, V. Q. Diep, J. Appenzeller and Z. H. Chen, Acs Nano8, 3807 (2014)], showed that the spin-transfer torque (STT) is enhanced by the asymmetry in a graphene lateral spin-valve structure. This lateral structure or geometry can be modeled by a four-terminal magnetic tunneling junction (MTJ) as opposite to the conventional two-terminal MTJ. In this paper, using the nonequilibrium Green’s function formalism (NEGF), we compare the anti-damping components of the STT in a similar nonconventional lateral one-dimensional MTJ with that in the conventional MTJ. We find that the lateral geometry renders enhanced anti-damping torques compared with the conventional one, provided that the barrier energy, the scattering length and the magnetization angle are in a certain parameter region. We also identify this parameter region in the presence of dephasing. The enhancement of the anti-damping torques declines when the scattering region is longer. For the four-terminal MTJ of larger scattering length, the dephasing can expedite the anti-damping torque.

Effect of a complicated many-body environment is analyzed on the chaotic motion of a quantum particle in a mesoscopic ballistic structure. The absorption and dephasing phenomena are treated on the same footing in the framework of a schematic microscopic model. The single-particle doorway resonance states excited in the structure via an external channel are damped not only because of the escape onto such channels but also due to ulterior population of the long-lived background states. The transmission through the structure is presented as an incoherent sum of the flow formed by the interfering damped doorway resonances and the retarded flow of the particles re-emitted by the environment.

We report our recent numerical study on the effects of dephasing on a perfectly conducting channel (PCC), its presence believed to be dominant in the transport characteristics of a zigzag graphene nanoribbons (GNR) and of a metallic carbon nanotubes (CNT). Our data confirms an earlier prediction that a PCC in GNR exhibits a peculiar robustness against dephasing, in contrast to that of the CNT. By studying the behavior of the conductance as a function of the system's length we show that dephasing destroys the PCC in CNT, whereas it stabilizes the PCC in GNR. Such opposing responses of the PCC against dephasing stem from a different nature of the PCC in these systems.