Time evolution and decoherence of entangled states realized in coupled superconducting flux qubits

TL;DR

This paper theoretically investigates how decoherence impacts entangled superposition states in coupled superconducting flux qubits, revealing the role of quantum fluctuations and identifying a decoherence-free subspace.

Contribution

It uncovers the influence of quantum fluctuations on decoherence and demonstrates the existence of a decoherence-free subspace in coupled flux qubits.

Findings

Quantum fluctuations significantly affect decoherence when observable expectation is zero.

Decoherence can be induced through higher-order quantum effects.

A decoherence-free subspace exists for charge-coupled environments.

Abstract

We study theoretically how decoherence affects superposition states composed of entangled states in inductively coupled two superconducting flux-qubits. We discover that the quantum fluctuation of an observable in a coupled flux-qubit system plays a crucial role in decoherence when the expectation value of the observable is zero. This examplifies that decoherence can be also induced through a quantum mechanically higher-order effect. We also find that there exists a decoherence free subspace for the environment coupled via a charge degree of freedom of the qubit system.