Abstract
Under the Born–Markov approximation, a qubit system, such as a two-level atom, is known to undergo a memoryless decay of quantum coherence or excitation when weakly coupled to a featureless environment. Recently, it has been shown that unavoidable disorder in the environment is responsible for non-Markovian effects and information backflow from the environment into the system owing to Anderson localization. This turns disorder into a resource for enhancing non-Markovianity in the system–environment dynamics, which could be of relevance in cavity quantum electrodynamics. Here we consider the decoherence dynamics of a qubit weakly coupled to a two-dimensional bath with a nontrivial topological phase, such as a two-level atom embedded in a two-dimensional coupled-cavity array with a synthetic gauge field realizing a quantum-Hall bath, and show that Markovianity is protected against moderate disorder owing to the robustness of chiral edge modes in the quantum-Hall bath. Interestingly, switching off the gauge field, i.e., flipping the bath into a topological trivial phase, allows one to re-introduce non-Markovian effects. Such a result indicates that changing the topological phase of a bath by a tunable synthetic gauge field can be harnessed to control non-Markovian effects and quantum information backflow in a qubit-environment system.
Highlights
Relaxation and decoherence dynamics in open quantum systems is attracting a continuous and increasing interest since more than three decades, with major relevance both in foundations of quantum physics, such as for the explanation of spontaneous quantum decay and the quantum to classical transition [1], as well as for a wide variety of physical problems ranging from quantum engineering to many-body systems and quantum information science [2,3], where irreversible dynamical behaviors such as energy dissipation, relaxation to a thermal equilibrium, and decay of quantum coherence and correlations are commonplace
In the majority of cases, where system and environment time scales are widely separated, the evolution of the reduced density matrix of a quantum system weakly coupled to a featureless environment is governed by a master equation of the Lindblad form, which describes a memoryless dynamics typically leading to an irreversible loss of quantum features
In summary we presented a study of the decoherence dynamics of a qubit embedded in a twodimensional disordered quantum Hall-bath, here embodied by a coupled cavity-array, in the weakcoupling regime, with a synthetic gauge field
Summary
Relaxation and decoherence dynamics in open quantum systems is attracting a continuous and increasing interest since more than three decades, with major relevance both in foundations of quantum physics, such as for the explanation of spontaneous quantum decay and the quantum to classical transition [1], as well as for a wide variety of physical problems ranging from quantum engineering to many-body systems and quantum information science [2,3], where irreversible dynamical behaviors such as energy dissipation, relaxation to a thermal equilibrium, and decay of quantum coherence and correlations are commonplace. It has been suggested and demonstrated that disorder in the bath can be exploited to realize strong coupling conditions for light–matter interaction [8,9] and to enhance non-Markovian effects [10,11] owing to Anderson localization [12]. In this work we investigate the decoherence and non-Markovian dynamics of a qubit interacting with a quantum bath with reconfigurable topological phase and with disorder. The main result of our analysis is that, while in a topologically-trivial quantum environment disorder induces strong memory effects owing to Anderson localization [10], flipping the topological phase of the bath into a non-trivial protects Markovianity against disorder in the system. Our results indicate that reconfigurable topological baths in connection with disorder can be exploited to controlling (either suppressing or enhancing) memory effects in open quantum systems
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