Spectroscopy of Three-Particle Entanglement in a Macroscopic Superconducting Circuit

TL;DR

This paper demonstrates three-particle entanglement in a macroscopic superconducting circuit through microwave spectroscopy, revealing complex spectra and potential for controllable qubit coupling in quantum computing.

Contribution

It provides experimental evidence of three-particle entanglement in a superconducting circuit and introduces a method for controllable coupling of distant qubits.

Findings

Strong coupling between each junction and the resonator observed.

Spectroscopic evidence of three-particle entanglement found.

Potential for controllable qubit coupling demonstrated.

Abstract

We study the quantum mechanical behavior of a macroscopic, three-body, superconducting circuit. Microwave spectroscopy on our system, a resonator coupling two large Josephson junctions, produced complex energy spectra well explained by quantum theory over a large frequency range. By tuning each junction separately into resonance with the resonator, we first observe strong coupling between each junction and the resonator. Bringing both junctions together into resonance with the resonator, we find spectroscopic evidence for entanglement between all three degrees of freedom and suggest a new method for controllable coupling of distant qubits, a key step toward quantum computation.