Cooling a nanomechanical resonator with quantum back-action

TL;DR

This paper demonstrates that quantum back-action from a superconducting single-electron transistor can be used to cool a nanomechanical resonator from 550mK to 300mK, revealing new possibilities for quantum control of mechanical systems.

Contribution

It reports the first observation of back-action-induced cooling of a nanomechanical resonator via a superconducting single-electron transistor, akin to laser cooling in atomic physics.

Findings

Cooling of resonator from 550mK to 300mK near transport resonance

Back-action effects depend on SSET bias conditions

Implications for quantum state preparation of mechanical systems

Abstract

Quantum mechanics demands that the act of measurement must affect the measured object. When a linear amplifier is used to continuously monitor the position of an object, the Heisenberg uncertainty relationship requires that the object be driven by force impulses, called back-action. Here we measure the back-action of a superconducting single-electron transistor (SSET) on a radiofrequency nanomechanical resonator. The conductance of the SSET, which is capacitively coupled to the resonator, provides a sensitive probe of the latter's position;back-action effects manifest themselves as an effective thermal bath, the properties of which depend sensitively on SSET bias conditions. Surprisingly, when the SSET is biased near a transport resonance, we observe cooling of the nanomechanical mode from 550mK to 300mK-- an effect that is analogous to laser cooling in atomic physics. Our measurements have implications for nanomechanical readout of quantum information devices and the limits of ultrasensitive force microscopy (such as single-nuclear-spin magnetic resonance force microscopy). Furthermore, we anticipate the use of these backaction effects to prepare ultracold and quantum states of mechanical structures, which would not be accessible with existing technology.