Antiresonances as precursors of decoherence

TL;DR

This paper demonstrates that antiresonances in complex spectra can serve as precursors to decoherence, leading to irreversibility in quantum transport even under a unitary Hamiltonian framework, especially in systems coupled to chaotic environments.

Contribution

It introduces a Hamiltonian-based model showing how antiresonances cause phase randomization and decoherence in quantum transport, linking microscopic phase fluctuations to irreversibility.

Findings

Antiresonances lead to phase randomization in complex spectra.

Decoherence arises from phase instabilities and coarse graining.

Conductance matches that with a fictitious voltage probe in Landauer-Büttiker formalism.

Abstract

We show that, in presence of a complex spectrum, antiresonances act as a precursor for dephasing enabling the crossover to a fully decoherent transport even within a unitary Hamiltonian description. This general scenario is illustrated here by focusing on a quantum dot coupled to a chaotic cavity containing a finite, but large, number of states using a Hamiltonian formulation. For weak coupling to a chaotic cavity with a sufficiently dense spectrum, the ensuing complex structure of resonances and antiresonances leads to phase randomization under coarse graining in energy. Such phase instabilities and coarse graining are the ingredients for a mechanism producing decoherence and thus irreversibility. For the present simple model one finds a conductance that coincides with the one obtained by adding a ficticious voltage probe within the Landauer-Buettiker picture. This sheds new light on how the microscopic mechanisms that produce phase fluctuations induce decoherence.