Approaching the standard quantum limit of mechanical torque sensing

Citations of this article
Mendeley users who have this article in their library.


Mechanical transduction of torque has been key to probing a number of physical phenomena, such as gravity, the angular momentum of light, the Casimir effect, magnetism, and quantum oscillations. Following similar trends as mass and force sensing, mechanical torque sensitivity can be dramatically improved by scaling down the physical dimensions, and therefore moment of inertia, of a torsional spring. Yet now, through precision nanofabrication and sub-wavelength cavity optomechanics, we have reached a point where geometric optimization can only provide marginal improvements to torque sensitivity. Instead, nanoscale optomechanical measurements of torque are overwhelmingly hindered by thermal noise. Here we present cryogenic measurements of a cavity-optomechanical torsional resonator cooled in a dilution refrigerator to a temperature of 25 mK, corresponding to an average phonon occupation of <n> = 35, that demonstrate a record-breaking torque sensitivity of 2.9 yNm/Hz^{1/2}. This a 270-fold improvement over previous optomechanical torque sensors and just over an order of magnitude from its standard quantum limit. Furthermore, we demonstrate that mesoscopic test samples, such as micron-scale superconducting disks, can be integrated with our cryogenic optomechanical torque sensing platform, in contrast to other cryogenic optomechanical devices, opening the door for mechanical torque spectroscopy of intrinsically quantum systems.




Kim, P. H., Hauer, B. D., Doolin, C., Souris, F., & Davis, J. P. (2016). Approaching the standard quantum limit of mechanical torque sensing. Nature Communications, 7.

Register to see more suggestions

Mendeley helps you to discover research relevant for your work.

Already have an account?

Save time finding and organizing research with Mendeley

Sign up for free