Measurement-based Synthesis of multi-qubit Entangled States in Superconducting Cavity QED

TL;DR

This paper demonstrates a measurement-based method to generate multi-qubit entangled states in superconducting cavity QED, analyzing the process's fidelity and entanglement dynamics under realistic experimental conditions.

Contribution

It introduces a novel measurement-based approach for synthesizing multi-qubit entangled states in superconducting systems, with detailed analysis of fidelity and entanglement evolution.

Findings

Entangled states can be generated faster than qubit decoherence times.

Fidelity and entanglement are maintained during the measurement process.

Decoherence and control imperfections impact the state synthesis, but states remain achievable.

Abstract

Entangled multi-qubit states may be generated through a dispersive collective QND measurement of superconducting qubits coupled to a microwave transmission line resonator. Using the quantum trajectory approach, we analyze the stochastic measurement traces that would be observed in experiments. We illustrate the synthesis of three-qubit W- and GHZ-states, and we analyze how the fidelity and the entanglement evolve in time during the measurement. We discuss the influence of decoherence and relaxation, as well as of imperfect control over experimental parameters. We show that the desired states can be generated on timescales much faster than the qubit decoherence rates.