Coherent dynamics of a flux qubit coupled to a harmonic oscillator

TL;DR

This paper demonstrates the entanglement and coherent control of a superconducting flux qubit coupled to a harmonic oscillator, advancing quantum information processing capabilities in solid-state systems.

Contribution

It presents the first experimental realization of entanglement between a flux qubit and a harmonic oscillator in superconducting circuits.

Findings

Successful generation of entangled states between qubit and oscillator

Observation of Rabi oscillations indicating coherent control

Microwave spectroscopy confirms entanglement and control

Abstract

In the emerging field of quantum computation and quantum information, superconducting devices are promising candidates for the implementation of solid-state quantum bits or qubits. Single-qubit operations, direct coupling between two qubits, and the realization of a quantum gate have been reported. However, complex manipulation of entangled states - such as the coupling of a two-level system to a quantum harmonic oscillator, as demonstrated in ion/atom-trap experiments or cavity quantum electrodynamics - has yet to be achieved for superconducting devices. Here we demonstrate entanglement between a superconducting flux qubit (a two-level system) and a superconducting quantum interference device (SQUID). The latter provides the measurement system for detecting the quantum states; it is also an effective inductance that, in parallel with an external shunt capacitance, acts as a harmonic oscillator. We achieve generation and control of the entangled state by performing microwave spectroscopy and detecting the resultant Rabi oscillations of the coupled system.