Unconventional mechanism of virtual-state population through dissipation

TL;DR

This paper reveals a novel phenomenon where virtual states in open quantum systems can become significantly populated over time, challenging traditional notions of their negligible presence, and introduces a new analytical method to understand this metastability.

Contribution

It introduces hierarchical adiabatic elimination, a new analytical approach to study metastable virtual state populations in open quantum systems.

Findings

Virtual states can attain sizable populations in long-term dynamics.

The hierarchical adiabatic elimination method provides analytical timescales for metastability.

Results are relevant for generating stable and metastable entangled states.

Abstract

Virtual states are a central concept in quantum mechanics. By definition, the probability of finding a quantum system in a virtual state should be vanishingly small at all times. In contrast to this notion, we report a phenomenon occurring in open quantum systems by which virtual states can acquire a sizable population in the long time limit, even if they are not directly coupled to any dissipative channel. This means that the situation where the virtual state remains unpopulated can be metastable. We describe this effect by introducing a two-step adiabiatic elimination method, that we termed hierarchical adiabatic elimination, which allows one to obtain analytical expressions of the timescale of metastability in general open quantum systems. We show how these results can be relevant for practical questions such as the generation of stable and metastable entangled states in dissipative systems of interacting qubits.