Shot Noise Spectrum of Open Dissipative Quantum Two-level Systems

TL;DR

This paper analyzes the current noise spectrum of dissipative quantum two-level systems (qubits), revealing how dissipation and system parameters influence noise characteristics and enabling extraction of decoherence rates.

Contribution

It introduces a combined (non-)Markovian master equation and correlation function approach to derive a noise formula applicable to various dissipation regimes.

Findings

Dephasing and relaxation rates can be extracted from noise in weak dissipation.

Weak dissipation reduces coherence-induced noise suppression.

Localization-delocalization transition affects low-frequency noise in strong dissipation.

Abstract

We study the current noise spectrum of qubits under transport conditions in a dissipative bosonic environment. We combine (non-)Markovian master equations with correlation functions in Laplace-space to derive a noise formula for both weak and strong coupling to the bath. The coherence-induced reduction of noise is diminished by weak dissipation and/or a large level separation (bias). For weak dissipation, we demonstrate that the dephasing and relaxation rates of the two-level system can be extracted from noise. In the strong dissipation regime, the localisation-delocalisation transition becomes visible in the low-frequency noise.