Demonstrating W-type Entanglement of Dicke-States in Resonant Cavity Quantum Electrodynamics

TL;DR

This paper demonstrates the generation of W-type entangled states in a cavity QED system with up to three qubits, highlighting nonlinear dynamics and entanglement characterization through quantum tomography.

Contribution

It provides experimental evidence of W-state entanglement in a resonant cavity with three qubits, including analysis of fidelity limitations due to crosstalk.

Findings

Observation of coherent vacuum Rabi oscillations

Generation of maximally entangled W states

Fidelity limited by crosstalk during simultaneous qubit manipulations

Abstract

Nonlinearity and entanglement are two important properties by which physical systems can be identified as non-classical. We study the dynamics of the resonant interaction of up to N=3 two-level systems and a single mode of the electromagnetic field sharing a single excitation dynamically. We observe coherent vacuum Rabi oscillations and their nonlinear speed up by tracking the populations of all qubits and the resonator in time. We use quantum state tomography to show explicitly that the dynamics generates maximally entangled states of the W class in a time limited only by the collective interaction rate. We use an entanglement witness and the threetangle to characterize the state whose fidelity F=78% is limited in our experiments by crosstalk arising during the simultaneous qubit manipulations which is absent in a sequential approach with F=91%.