Abstract
The design and optimization of new-generation solid-state quantum hardware absolutely requires reliable dissipation versus decoherence models. Depending on the device operational condition, the latter may range from Markov-type schemes (both phenomenological- and microscopic- like) to quantum-kinetic approaches. The primary goal of this paper is to review in a cohesive way virtues versus limitations of the most popular approaches, focussing on a few critical issues recently pointed out (see, e.g., Phys. Rev. B 90, 125140 (2014); Eur. Phys. J. B 90, 250 (2017)) and linking them within a common framework. By means of properly designed simulated experiments of a prototypical quantum-dot nanostructure (described via a two-level electronic system coupled to a phonon bath), we shall show that both conventional (i.e., non-Lindblad) Markov models and density-matrix-based non-Markov approaches (i.e., quantum-kinetic treatments) may lead to significant positivity violations. While for the former case the problem is easily avoidable by choosing genuine Lindblad-type dissipation models, for the latter, a general strategy is still missing.
Highlights
Quantum-mechanical state superposition and correlation are the key players for the concrete realization of quantum information processing devices [1,2]
For purely atomic and/or photonic systems, dissipation and decoherence phenomena may successfully be treated via adiabatic-decoupling schemes [8] in terms of extremely simplified models based on a few key parameters; within such effective treatments, the main goal is to derive a suitable form of the system-environment Liouville superoperator, able to preserve the positivity of the system density matrix [10]
By means of properly designed simulated experiments of a prototypical quantum-dot nanostructure, we shall show the following: (i) conventional Markov models may lead to significant positivity violations; (ii) such intrinsic limitations may be avoided adopting properly designed Lindblad-type Markov schemes; (iii) density-matrix-based non-Markov models, namely quantum-kinetic treatments, may lead to positivity violations as well
Summary
Quantum-mechanical state superposition and correlation (i.e., entanglement) are the key players for the concrete realization of quantum information processing devices [1,2]. For purely atomic and/or photonic systems, dissipation and decoherence phenomena may successfully be treated via adiabatic-decoupling schemes [8] in terms of extremely simplified models based on a few key parameters; within such effective treatments, the main goal is to derive a suitable form of the system-environment Liouville superoperator, able to preserve the positivity of the system density matrix [10]. This is typically accomplished by identifying so-called Lindblad superoperators [11] expressed in terms of a few crucial system–environment coupling constants.
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