Cooling the Motion of Diamond Nanocrystals in a Magneto-Gravitational Trap in High Vacuum

TL;DR

This paper demonstrates a magneto-gravitational trapping method for diamond nanocrystals in high vacuum, achieving feedback cooling of their motion to below 1 Kelvin, offering an alternative to optical trapping.

Contribution

It introduces a stable magneto-gravitational trapping technique for nanodiamonds, enabling effective cooling without optical heating issues.

Findings

Successful stable levitation from atmospheric pressure to high vacuum.

Feedback cooling reduces motion to below 1 Kelvin.

Magneto-gravitational trap is a viable alternative to optical traps.

Abstract

Levitated diamond nanocrystals with nitrogen-vacancy (NV) centres in high vacuum have been proposed as a unique system for experiments in fundamental quantum mechanics, including the generation of large quantum superposition states and tests of quantum gravity. This system promises extreme isolation from its environment while providing quantum control and sensing through the NV centre spin. While optical trapping has been the most explored method of levitation, recent results indicate that excessive optical heating of the nanodiamonds under vacuum may make the method impractical with currently available materials. Here, we study an alternative magneto-gravitational trap for diamagnetic particles, such as diamond nanocrystals, with stable levitation from atmospheric pressure to high vacuum. Magnetic field gradients from permanent magnets confine the particle in two dimensions, while confinement in the third dimension is gravitational. We demonstrate that feedback cooling of the centre-of-mass motion of a trapped nanodiamond cluster results in cooling of one degree of freedom to less than 1 K.