Ground state cooling of a nanomechanical resonator via a Cooper pair box qubit

TL;DR

This paper proposes a method to cool a nanomechanical resonator to its ground state using a Cooper-pair box qubit, leveraging Lorentz force coupling and a detuned drive, with analytical analysis of cooling efficiency.

Contribution

It introduces a novel scheme for ground state cooling of a nanomechanical beam via a CPB qubit with analytical expressions for cooling dynamics.

Findings

Cooling is optimized in a strong drive regime.

Analytical expressions for cooling rate and final occupation number are derived.

Necessary conditions for achieving ground-state cooling are identified.

Abstract

In this paper we present a scheme for ground state cooling of a flexural mode of a nanomechanical beam incorporated in a loop-shaped Cooper-pair box (CPB) circuit. Via the Lorentz force coupling of the beam motion to circulating CPB-circuit currents, energy is transferred to the CPB qubit which acts as a dissipative two-level system. The cooling process is driven by a detuned gate-voltage drive acting on the CPB. We analyze the cooling force spectrum and present analytical expressions for the cooling rate and final occupation number for a wide parameter regime. In particular, we find that cooling is optimized in a strong drive regime, and we present the necessary conditions for ground-state cooling.