Characterisation of a charged particle levitated nano-oscillator

Abstract

We describe the construction and characterisation of a nano-oscillator formed by a Paul trap. The frequency and temperature stability of the nano-oscillator was measured over several days allowing us to identify the major sources of trap and environmental fluctuations. We measure an overall frequency stability of 2 ppm/hr and a temperature stability of more than 5 hours via the Allan deviation. Importantly, we find that the charge on the nanoscillator is stable over a timescale of at least two weeks and that the mass of the oscillator, can be measured with a 3 % uncertainty. This allows us to distinguish between the trapping of a single nanosphere and a nano-dumbbell formed by a cluster of two nanospheres.

Ultranarrow-linewidth levitated nano-oscillator for testing dissipative wave-function collapse

“…Here we present data acquired by monitoring a single nanoparticle of mass m = 9.6 ± 0.4 ± 0.9 × 10 −17 kg [37] obtained by inducing a change of the total charge by one elementary charge by and measuring the resulting shift in the trap frequency [21]. Assuming a nominal density of ρ = 1850 kg/m 3 this corresponds to a radius of r = 231 ± 7 nm.…”

“…We create our levitated nano-oscillator by trapping commercial silica nanospheres of radius 230 nm in high vacuum within a linear Paul trap [21] shown schematically in Fig. 1.…”

“…Along one diagonal the electrodes are grounded and on the other two they are driven by an AC electric field which provides a trapping potential in the plane perpendicular to the rods axis. To generate 3D confinement, two additional ring end-cap electrodes, coaxial with the trap and printed directly on the PCB holders (not shown [21]), are kept at a DC constant voltage. The particles are injected in low vacuum (∼10 −1 mbar) by means of electrospray ionization.…”

“…In contrast, a charged nanoparticle that is levitated using electrodynamic fields within a Paul trap, is an attractive levitated system as it is free from recoil induced heating [5,6] as only low light intensities are required for detection. In addition, large well depths in excess of 1 eV (up to 10 6 K) allow operation of the trap in the harmonic regime, even for temperatures exceeding 300 K. We have recently demonstrated [21] that the charge on nanosphere in a Paul trap is stable over many weeks of measurement allowing stable oscillation frequencies limited only by the noise and drifts in the applied electric fields and environmental disturbances.…”

Quantum sensing with nanoparticles for gravimetry: when bigger is better

“…Unique to levitated optomechanics is the need for a launch and recapture method, since nanospheres are not indistinguishable like atoms. So far, loading at low vacuum pressure has been achieved through (i) momentum imparted by either a piezo-speaker [41] or a laser induced acoustic shock of a wafer covered by tethered nanorods [93], (ii) electrospray injection of particles [94], or (iii) conveyor-belt loading using optical [95] or electrical forces [94]. Reliable recapture of a levitated nanosphere still remains a technical challenge but can be built upon successful proof of principle demonstrations [96].…”