26th Australian Institute of Physics Congress and the Australian and New Zealand Conference on Optics and Photonics

Toward mechanically-detected magnetic resonance at the single spin limit

Not scheduled

20m

Belinda Hutchinson Building (The University of Sydney )

Contributed Oral AIP | Quantum Science and Technology (QST)

Description

The nitrogen-vacancy (NV) centre in diamond provides a robust platform for quantum experiments owing to the long spin coherence time of the triplet state in the NV- charge state. Nanodiamonds that host a single NV centre offer a feasible platform to demonstrate a macroscopic quantum superposition state, which possesses applications in inertial sensing and precision tests of physics. However, this demands isolation from gas collisions and mechanical and thermal noise, which can be achieved through levitation of the nanodiamond under vacuum.

We discuss progress towards detecting single-spin torques by monitoring the motion of a levitated nanodiamond. Using a Paul trap constructed from a hairpin-shaped length of tungsten wire, we load microdiamonds at atmospheric pressure. Then, after pumping the chamber to below 1 mbar, we can spectrally resolve the levitated particle’s motional modes using laser light scattered from the particle. We can then derive a cooling signal from this scattering signal to suppress thermal, librational and motional noise. This approach has been shown to stabilise NDs and other nanoparticles in ion traps at vacuum exceeding 10-8 mbar. Further, we are investigating the optimisation of Paul trap electrode geometries through direct Langevin equation simulations of a charged microdiamond. With this, we can anticipate geometries that provide greater trap stability at a given electrode voltage. If we can cool librational modes to the mK regime, their contributions to the scattered signal become negligible compared to the tiny perturbations imposed on the particle’s orientation through the controlled flips of the single NV spin.

Optical tweezers also provide a pathway to motional cooling. Using diamond-silica core-shell nanoparticles, radiative cooling can effectively offset laser absorption under vacuum, preventing graphitisation of the core. These all-optical traps can similarly be cooled using electrodes and scattered signal from the trapping laser.