Charge Oscillations in Superconducting Nanodevices Coupled to External Environments

TL;DR

This paper compares two explanations for charge oscillations in superconducting nanodevices, showing that occupation number states are less stable than coherent states when coupled to noise, challenging the traditional quantum coherence interpretation.

Contribution

It demonstrates the instability of occupation number states versus coherent states in superconducting devices under noise, offering an alternative classical explanation for charge oscillations.

Findings

Occupation number states are more unstable under noise.

Coherent states remain stable when coupled to external dissipation.

Challenges the quantum coherence interpretation of charge oscillations.

Abstract

Charge oscillations in certain nanodevices, more specifically the so-called Superconducting Cooper Pair Boxes (SCB), are usually interpreted as an effect of macroscopic quantum coherence; an alternative explanation is however possible in terms of the Gross-Pitaewski equation for the classical order parameter. These two explanations are based on different quantum states assigned to the SCB, occupation number states in the first case, coherent-like states in the second one. We show that, when the SCB is weakly coupled to an external source of noise and dissipation, occupation number states are much more unstable than coherent ones.