Monitoring Entanglement Evolution and Collective Quantum Dynamics

TL;DR

This paper extends a quantum monitoring scheme to complex multi-qubit dynamics, enabling observation of entanglement and collective behaviors with high temporal resolution and low disturbance.

Contribution

It introduces a generalized measurement approach for complex quantum systems, including multi-frequency dynamics and entanglement, using lock-in techniques.

Findings

Successful monitoring of Landau-Zener transitions in qubits

Proposed measurement of entanglement between two qubits

Method for observing collective dynamics in qubit arrays

Abstract

We generalize a recently developed scheme for monitoring coherent quantum dynamics with good time-resolution and low backaction [Reuther et al., Phys. Rev. Lett. 102, 033602 (2009)] to the case of more complex quantum dynamics of one or several qubits. The underlying idea is to measure with lock-in techniques the response of the quantum system to a high-frequency ac field. We demonstrate that this scheme also allows one to observe quantum dynamics with many frequency scales, such as that of a qubit undergoing Landau-Zener transitions. Moreover, we propose how to measure the entanglement between two qubits as well as the collective dynamics of qubit arrays.