Temperature can enhance coherent oscillations at a Landau-Zener transition

TL;DR

This paper explores how temperature and high-frequency environments can unexpectedly enhance quantum coherent oscillations during a Landau-Zener transition, revealing a novel Lamb-assisted effect that could serve as an experimental probe.

Contribution

It introduces the concept of Lamb-assisted coherent oscillations, showing that high-frequency environments and increased temperature can exponentially boost quantum coherence during Landau-Zener transitions.

Findings

Decoherence suppresses quantum superpositions as expected.

Lamb shift can exponentially enhance coherent oscillations.

High-frequency environments and temperature increase lead to exponential growth in oscillation amplitude.

Abstract

We consider sweeping a system through a Landau-Zener avoided-crossing, when that system is also coupled to an environment or noise. Unsurprisingly, we find that decoherence suppresses the coherent oscillations of quantum superpositions of system states, as superpositions decohere into mixed states. However, we also find an effect we call "Lamb-assisted coherent oscillations", in which a Lamb shift exponentially enhances the coherent oscillation amplitude. This dominates for high-frequency environments such as super-Ohmic environments, where the coherent oscillations can grow exponentially as either the environment coupling or temperature are increased. The effect could be used as an experimental probe for high-frequency environments in such systems as molecular magnets, solid-state qubits, spin-polarized gases (neutrons or He3) or Bose-condensates.