Decoherence and control of a qubit in spin baths: an exact master equation study

Jing, Jun; Wu, Lian-Ao

doi:10.1038/s41598-018-19977-9

Cited by 35 publications

(35 citation statements)

References 41 publications

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“…The Hamiltonian (2) effectively describes various systems, e.g., nuclear spin baths in quantum dots [37,38], nitrogen-vacancy (NV) centers [39], nuclear magnetic resonance systems [40], microcavities hosting multi-atom systems [41,42] or multiple superconducting qubits [36,43], and molecular nanomagnets [44,45].…”

Section: Discussionmentioning

confidence: 99%

Collectively enhanced thermalization via multiqubit collisions

et al. 2019

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We investigate the evolution of a target qubit caused by its multiple random collisions with N -qubit clusters. Depending on the cluster state, the evolution of the target qubit may correspond to its effective interaction with a thermal bath, a coherent (laser) drive, or a squeezed bath. In cases where the target qubit relaxes to a thermal state its dynamics can exhibit a quantum advantage, whereby the target-qubit temperature can be scaled up proportionally to N 2 and the thermalization time can be shortened by a similar factor, provided the appropriate coherence in the cluster is prepared by non-thermal means. We dub these effects quantum super-thermalization due to its analogies to super-radiance. Experimental realizations of these effects are suggested.

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Section: Discussionmentioning

confidence: 99%

Collectively enhanced thermalization via multiqubit collisions

et al. 2019

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“…While this approximation sufficiently describes quantum thermodynamics, decoherence or the behaviour of magnetic resonance and similar techniques in many situations, it misses that during the memory time, even if it is short, the system and environment have a joint evolution in which in particular the excitation of the environment can act back on the system. This partially coherent backaction not only shapes the system's short time dynamics but can also leave an imprint in the long arXiv:1905.11422v1 [cond-mat.mes-hall] 27 May 2019 time behaviour in the form of a correction to the expected Markovian dynamics [13][14][15] or a modification of the performance in thermal machines [16]. Such properties can thus be used passively as a diagnostic tool for the structure of the environment.…”

Section: Introductionmentioning

confidence: 99%

Coherent backaction between spins and an electronic bath: Non-Markovian dynamics and low-temperature quantum thermodynamic electron cooling

et al. 2019

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We provide a general analytical framework for calculating the dynamics of a spin system in contact with a bath beyond the Markov approximation. The approach is based on a systematic expansion of the Nakashima-Zwanzig master equation in the weak-coupling limit but makes no assumption on the time dynamics and includes all quantum coherent memory effects leading to non-Markovian dynamics. Our results describe, for the free induction decay, the full time range from the non-Markovian dynamics at short times, to the well-known exponential thermal decay at long times. We provide full analytic results for the entire time range using a bath of itinerant electrons as an archetype for universal quantum fluctuations. Furthermore, we propose a quantum thermodynamic scheme to employ the temperature insensitivity of the non-Markovian decay to transport heat out of the electron system and thus, by repeated re-initialisation of a cluster of spins, to efficiently cool the electrons at very low temperatures.

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“…In our attempt, we face a serious difficulty in diagonalizing the spin bath Hamiltonian, either analytically or numerically, for larger number of spins in the environment. Although, analytic solutions do exist for constant coupling 36 and some special forms of time dependent coupling 37 , general solution for arbitrary forms of system-environment coupling of the spin bath Hamiltonian are hard to find. We therefore, try to circumvent the problem by choosing a simple model, which we argue, is a close approximation to the spin bath model for low temperatures.…”

Section: Introductionmentioning

confidence: 99%

Non-Markovianity of qubit evolution under the action of spin environment

Chakraborty

Mallick

Mandal

et al. 2019

Sci Rep

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The question, whether an open system dynamics is Markovian or non-Markovian can be answered by studying the direction of the information flow in the dynamics. In Markovian dynamics, information must always flow from the system to the environment. If the environment is interacting with only one of the subsystems of a bipartite system, the dynamics of the entanglement in the bipartite system can be used to identify the direction of information flow. Here we study the dynamics of a two-level system interacting with an environment, which is also a heat bath, and consists of a large number of two-level quantum systems. Our model can be seen as a close approximation to the ‘spin bath’ model at low temperatures. We analyze the Markovian nature of the dynamics, as we change the coupling between the system and the environment. We find the Kraus operators of the dynamics for certain classes of couplings. We show that any form of time-independent or time-polynomial coupling gives rise to non-Markovianity. Also, we witness non-Markovianity for certain parameter values of time-exponential coupling. Moreover, we study the transition from non-Markovian to Markovian dynamics as we change the value of coupling strength.

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Decoherence and control of a qubit in spin baths: an exact master equation study

Cited by 35 publications

References 41 publications

Collectively enhanced thermalization via multiqubit collisions

Collectively enhanced thermalization via multiqubit collisions

Coherent backaction between spins and an electronic bath: Non-Markovian dynamics and low-temperature quantum thermodynamic electron cooling

Non-Markovianity of qubit evolution under the action of spin environment

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