Mechanism for quantum speedup in open quantum systems

TL;DR

This paper identifies that the formation of system-environment bound states, rather than non-Markovian effects alone, is the key to quantum speedup in open quantum systems, with implications for experimental realization.

Contribution

It reveals that bound state formation, linked to the energy spectrum, is the essential mechanism for quantum speedup, offering a new perspective beyond non-Markovian dynamics.

Findings

Bound states are crucial for quantum speedup.

Non-Markovianity is a dynamical but not fundamental factor.

Potential for experimental observation in circuit QED.

Abstract

The quantum speed limit (QSL) time for open system characterizes the most efficient response of the system to the environmental influences. Previous results showed that the non-Markovianity governs the quantum speedup. Via studying the dynamics of a dissipative two-level system, we reveal that the non-Markovian effect is only the dynamical way of the quantum speedup, while the formation of the system-environment bound states is the essential reason for the quantum speedup. Our attribution of the quantum speedup to the energy-spectrum character can supply another vital path for experiments when the quantum speedup shows up without any dynamical calculations. The potential experimental observation of our quantum speedup mechanism in the circuit QED system is discussed. Our results may be of both theoretical and experimental interests in exploring the ultimate QSL in realistic environments, and may open new perspectives for devising active quantum speedup devices.