Probing the quantum coherence of a nanomechanical resonator using a superconducting qubit II: Implementation

TL;DR

This paper proposes an implementation of quantum superposition generation and detection in a nanomechanical resonator using circuit QED with superconducting qubits, comparing charge and flux qubit realizations.

Contribution

It details a feasible setup for creating and detecting quantum superpositions in nanomechanical systems using superconducting qubits within circuit QED.

Findings

Both charge and flux qubits show similar coupling strengths.

The implementation is practical with current superconducting circuit technology.

The setup enables probing quantum coherence in mechanical resonators.

Abstract

We describe a possible implementation of the nanomechanical quantum superposition generation and detection scheme described in the preceding, companion paper [Armour A D and Blencowe M P 2008 New. J. Phys. Submitted]. The implementation is based on the circuit quantum electrodynamics (QED) set-up, with the addition of a mechanical degree of freedom formed out of a suspended, doubly-clamped segment of the superconducting loop of a dc SQUID located directly opposite the centre conductor of a coplanar waveguide (CPW). The relative merits of two SQUID based qubit realizations are addressed, in particular a capacitively coupled charge qubit and inductively coupled flux qubit. It is found that both realizations are equally promising, with comparable qubit-mechanical resonator mode as well as qubit-microwave resonator mode coupling strengths.