Dissipative dynamics of superconducting hybrid qubit systems

TL;DR

This paper provides a theoretical analysis of superconducting hybrid qubit systems, focusing on their energy spectra and dissipative dynamics under different decoherence scenarios, using the Bloch-Redfield formalism.

Contribution

It introduces a detailed theoretical framework for analyzing energy levels and decoherence in hybrid charge-phase qubit systems with sigma(x)xsigma(z) coupling.

Findings

Energy crossing and anti-crossing features depend on inter-qubit coupling strength.

Dephasing and relaxation rates vary with heat bath temperature.

System's populations and coherences are explicitly calculated.

Abstract

We perform a theoretical study of composite superconducting qubit systems for the case of a coupled qubit configuration based on a hybrid qubit circuit made of both charge and phase qubits, which are coupled via a sigma(x)xsigma(z) interaction. We compute the system's eigen-energies in terms of the qubit transition frequencies and the strength of the inter-qubit coupling, and describe the sensitivity of the energy crossing/anti-crossing features to such coupling. We compute the hybrid system's dissipative dynamics for the cases of i) collective and ii) independent decoherence, whereby the system interacts with one common and two different baths of harmonic oscillators, respectively. The calculations have been performed within the Bloch-Redfield formalism and we report the solutions for the populations and the coherences of the system's reduced density matrix. The dephasing and relaxation rates are explicitly calculated as a function of the heat bath temperature.