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Radiofrequency traps are used to confine charged particles but are only stable for a narrow range of charge-to-mass ratios. Here, we confine two particles -- a nanoparticle and an atomic ion -- in the same radiofrequency trap although their charge-to-mass ratios differ by six orders of magnitude. The confinement is enabled by a dual-frequency voltage applied to the trap electrodes. We introduce a robust loading procedure under ultra-high vacuum and characterize the stability of both particles. It is observed that slow-field micromotion, an effect specific to the dual-field setting, plays a crucial role for ion localization and will be important to account for when engineering controlled interactions between the particles., Comment: 4 figures

Levitated dipolar scatterers exhibit exceptional performance as optomechanical systems for observing quantum mechanics at the mesoscopic scale. However, their tendency to scatter light in almost any direction poses experimental challenges, in particular limiting light collection efficiencies and, consequently, the information extractable from the system. In this article, we present a setup designed to enhance the information gleaned from optomechanical measurements by constraining the back action to a specific spatial direction. This approach facilitates achieving Heisenberg-limited detection at any given numerical aperture. The setup consists of a hollow hemispherical mirror that controls the light scattered by the dipolar emitter, particularly at high scattering angles, thereby focusing the obtained information. This mirror is compatible with existing setups commonly employed in levitated optomechanics, including confocal lenses and optical resonators.

Levitated nanoparticles in vacuum are prime candidates for generating macroscopic quantum superposition states of massive objects. Most protocols for preparing these states necessitate coherent expansion beyond the scale of the zero-point motion to produce sufficiently delocalized and pure phase-space distributions. Here, we spatially expand and subsequently recontract the thermal state of a levitated nanoparticle by modifying the stiffness of the trap holding the particle. We achieve state-expansion factors of 25 in standard deviation for a particle initially feedback-cooled to a center-of-mass thermal state of \SI{155}{\milli\kelvin}. Our method relies on a hybrid scheme combining an optical trap, for cooling and measuring the particle's motion, with a Paul trap for expanding its state. Consequently, state expansion occurs devoid of measurement backaction from photon recoil, making this approach suitable for coherent wavefunction expansion in future experiments.

We present a hybrid trapping platform that allows us to levitate a charged nanoparticle in high vacuum using either optical fields, radio-frequency fields, or a combination thereof. Our hybrid approach combines an optical dipole trap with a linear Paul trap while maintaining a large numerical aperture (0.77 NA). We detail a controlled transfer procedure that allows us to use the Paul trap as a safety net to recover particles lost from the optical trap at high vacuum. The presented hybrid platform adds to the toolbox of levitodynamics and represents an important step towards fully controllable dark potentials, providing control in the absence of decoherence due to photon recoil., Comment: 7 pages, 4 figures

A levitated nanomechanical oscillator under ultra-high vacuum (UHV) is highly isolated from its environment. It has been predicted that this isolation leads to very low mechanical dissipation rates. However, a gap persists between predictions and experimental data. Here, we levitate a silica nanoparticle in a linear Paul trap at room temperature, at pressures as low as $7\times10^{-11}$ mbar. We measure a dissipation rate of $2\pi\times69(22)$ nHz, corresponding to a quality factor exceeding $10^{10}$, more than two orders of magnitude higher than previously shown. A study of the pressure dependence of the particle's damping and heating rates provides insight into the relevant dissipation mechanisms.

Cooling the center-of-mass motion of levitated nanoparticles provides a route to quantum experiments at mesoscopic scales. Here we demonstrate three-dimensional sympathetic cooling and detection of the center-of-mass motion of a levitated silica nanoparticle. The nanoparticle is electrostatically coupled to a feedback-cooled particle while both particles are trapped in the same Paul trap. We identify two regimes, based on the strength of the cooling: in the first regime, the sympathetically cooled particle thermalizes with the directly cooled one, while in the second regime, the sympathetically cooled particle reaches a minimum temperature. This result provides a route to efficiently cool and detect particles that cannot be illuminated with strong laser light, such as absorptive particles, and paves the way for controlling the motion of arrays of several trapped nanoparticles.

We confine a microparticle in a hybrid potential created by a Paul trap and a dual-beam optical trap. We transfer the particle between the Paul trap and the optical trap at different pressures and study the influence of feedback cooling on the transfer process. This technique provides a path for experiments with optically levitated particles in ultra-high vacuum and in potentials with complex structures.

Interferometric methods for detecting the motion of a levitated nanoparticle provide a route to the quantum ground state, but such methods are currently limited by mode mismatch between the reference beam and the dipolar field scattered by the particle. Here we demonstrate a self-interference method to detect the particle's motion that solves this problem. A Paul trap confines a charged dielectric nanoparticle in high vacuum, and a mirror retro-reflects the scattered light. We measure the particle's motion with a sensitivity of $1.7\times 10^{-12} \text{m}/\sqrt{\text{Hz}}$, corresponding to a detection efficiency of 2.1%, with a numerical aperture of 0.18. As an application of this method, we cool the particle, via feedback, to temperatures below those achieved in the same setup using a standard position measurement., Comment: 12 pages, 8 figures

We describe a technique to measure the position of a dipolar scatterer based on self-homodyne detection of the scattered light. The method can theoretically reach the Heisenberg limit, at which information gained about the position is constrained only by the back-action of the scattered light. The technique has applications in the fields of levitated optomechanics and trapped ions and is generally applicable to the position determination of confined light scatterers., Comment: 11 pages, 5 figures

All three motional modes of a charged dielectric nanoparticle in a Paul trap are cooled by direct feedback to temperatures of a few mK. We test two methods, one based on electrical forces and the other on optical forces; for both methods, we find similar cooling efficiencies. Cooling is characterized for both feedback forces as a function of feedback parameters, background pressure, and the particle's position.

Mechanical oscillators based on levitated particles are promising candidates for sensitive detectors and platforms for testing fundamental physics. The targeted quality factors for such oscillators correspond to extremely low damping rates of the center-of-mass motion, which can only be obtained if the particles are trapped in ultrahigh vacuum (UHV). In order to reach such low pressures, a noncontaminating method of loading particles in a UHV environment is necessary. However, loading particle traps at pressures below the viscous flow regime is challenging due to the conservative nature of trapping forces and reduced gas damping. We demonstrate a technique that allows us to overcome these limitations and load particles into a Paul trap at pressures as low as 4x10^-7 mbar. The method is based on laser-induced acoustic desorption of nanoparticles from a metallic foil and temporal control of the Paul trap potential. We show that the method is highly efficient: More than half of the trapping attempts are successful. Moreover, since trapping attempts can be as short as a few milliseconds, the technique provides high throughput of loaded particles. Finally, the efficiency of the method does not depend on pressure, indicating that the method should be extensible to UHV., Comment: 5 pages, 5 figures

Optically levitated micro- and nanoparticles offer an ideal playground for investigating photon-phonon interactions over macroscopic distances. Here we report the observation of long-range optical binding of multiple microparticles, mediated by intermodal scattering and interference inside the evacuated core of a hollow-core photonic crystal fibre (HC-PCF). Three polystyrene particles with 1 {\mu}m diameter are stably bound together with an inter-particle distance of ~40 {\mu}m, or 50 times longer than the wavelength of the trapping laser. The bound-particle array can be translated to-and-fro over centimetre distances along the fibre. When evacuated to 6 mbar gas pressure, the collective mechanical modes of the bound-particle array could be observed. The measured inter-particle distance at equilibrium and mechanical eigen-frequencies are supported by a novel analytical formalism modelling the dynamics of the binding process. The HC-PCF system offers a unique platform for investigating the rich optomechanical dynamics of arrays of levitated particles in a well-isolated and protected environment.