Quantum effective action for dissipative semiclassical dynamics

TL;DR

This paper derives quantum corrections to semiclassical Langevin dynamics using the quantum effective action in the Schwinger-Keldysh formalism, with applications to superconducting and bosonic junctions.

Contribution

It introduces a method to compute quantum corrections to dissipative semiclassical dynamics and applies it to physical systems like Josephson and bosonic junctions.

Findings

Quantum corrections are linked to zero-point energy at classical frequencies.

Quantum effects can reach percent levels in realistic superconducting systems.

The approach connects quantum effective action with dissipative classical dynamics.

Abstract

Using the quantum effective action in the Schwinger-Keldysh formalism, we derive quantum corrections to the semiclassical Langevin dynamics of a dissipative system governed by a macroscopic degree of freedom. We discuss the connection with the Ehrenfest theorem and show that, in the low-temperature and weak-damping regime, quantum corrections are determined by the zero-point energy of fluctuations evaluated at the classical underdamped frequency, closely paralleling the conservative case. We apply these general results to the resistively and capacitively shunted superconducting Josephson junction and to an elongated bosonic junction, where quantum corrections can reach the percent level under realistic conditions.