Modeling Energy Relaxation via Quantum Thermalization: A Superconducting Qubit Coupled to a Many-Body TLS System

TL;DR

This paper models how a superconducting qubit's energy relaxation is influenced by thermalization with a many-body TLS system, revealing exponential decay and scaling laws that deepen understanding of decoherence mechanisms.

Contribution

It introduces a numerical model of qubit relaxation via many-body TLS thermalization, highlighting the suppression of coherent exchange and identifying key parameters affecting relaxation times.

Findings

Thermalization leads to exponential energy decay.

Relaxation times scale as J^{-2} with coupling strength.

TLS internal properties significantly influence qubit relaxation.

Abstract

While two-level systems (TLS) in superconducting qubits are known to introduce phonon-mediated energy dissipation channels, many-body TLS systems themselves can also act as a distinct dissipation channel whose effect on qubit energy relaxation remains to be explored. In this work, we model and numerically simulate the irreversible thermalization-driven energy relaxation of a superconducting qubit coupled to a many-body TLS system. Our numerical results show that thermalization suppresses coherent energy exchange between the qubit and TLS, resulting in exponential energy decay. The relaxation times scale as $T_1, T_2 \propto J^{-2}$, where $J$ denotes the qubit-TLS coupling strength. Moreover, $T_1$ is significantly affected by the internal coupling strength of the TLS system, the TLS frequency fluctuation rate, and the number of thermally excited TLS. This work provides a quantum thermalization perspective for understanding qubit energy relaxation and decoherence, with potential implications for decoherence scenarios in other open quantum systems.