Entanglement of superconducting charge qubits by homodyne measurement

TL;DR

This paper proposes a scheme using homodyne measurement of a microwave resonator to generate high-fidelity entanglement between two superconducting charge qubits, functioning efficiently at short timescales.

Contribution

It introduces a novel protocol for entangling superconducting charge qubits via homodyne measurement, enabling high-fidelity entanglement with significant probability.

Findings

Entanglement fidelity can be made arbitrarily high.

The protocol achieves a success probability approaching 0.5.

Entanglement occurs at shorter timescales than revival phenomena.

Abstract

We present a scheme by which projective homodyne measurement of a microwave resonator can be used to generate entanglement between two superconducting charge qubits coupled to this resonator. The non-interacting qubits are initialised in a product of their ground states, the resonator is initialised in a coherent field state, and the state of the system is allowed to evolve under a rotating wave Hamiltonian. Making a homodyne measurement on the resonator at a given time projects the qubits into an state of the form (|gg> + exp(-i phi)|ee>)/sqrt(2). This protocol can produce states with a fidelity as high as required, with a probability approaching 0.5. Although the system described is one that can be used to display revival in the qubit oscillations, we show that the entanglement procedure works at much shorter timescales.