Synthesis of maximally entangled mixed states and disentanglement in coupled Josephson charge qubits

TL;DR

This paper explores how to controllably generate and analyze maximally entangled mixed states in a system of two coupled superconducting charge qubits, revealing phenomena like entanglement sudden death.

Contribution

It demonstrates a method to synthesize maximally entangled mixed states and characterizes entanglement dynamics, including sudden death, in coupled Josephson charge qubits.

Findings

Maximally entangled mixed states can be generated at specific times.

Entanglement exhibits sudden death and revival phenomena.

The study provides insights into entanglement sharing in superconducting qubits.

Abstract

We analyze a controllable generation of maximally entangled mixed states of a circuit containing two-coupled superconducting charge qubits. Each qubit is based on a Cooper pair box connected to a reservoir electrode through a Josephson junction. Illustrative variational calculations were performed to demonstrate the effect on the two-qubits entanglement. At sufficiently deviation between the Josephson energies of the qubits and/or strong coupling regime, maximally entangled mixed states at certain instances of time is synthesized. We show that entanglement has an interesting subsequent time evolution, including the sudden death effect. This enables us to completely characterize the phenomenon of entanglement sharing in the coupling of two superconducting charge qubits, a system of both theoretical and experimental interest.