arXiv subjects

Martin Frimmer

Publications and source records attributed to Martin Frimmer.

At least 19 recordsLinked to original sources

arXiv2026

Single-atom detection with a quantum-controlled mechanical oscillator

Using supersonic expansion, we create a time-gated, directional beam of Xe atoms with a narrow momentum distribution and detect their collisions with a levitated nanosphere cooled to its quantum ground state. We observe individual momentum kicks below 50 keV/c with 96% confidence and distinguish directional momentum transfer from the atomic beam against the background of thermal collisions. Our experiments constitute a first step toward the exploration of distance-dependent short-range interactions between atoms and levitated systems, as well as toward the use of levitated platforms for impulsive force sensing in previously unexplored parameter regimes.

quant-ph↗

arXiv2026

Shot-to-shot noise cancellation for parametric oscillators

Powerful approaches to squeeze the motional state of a harmonic oscillator rely on the stepwise modulation of its resonance frequency. Such protocols can be limited by forces that vary slowly between experimental runs but are constant during a single experimental shot. Such shot-to-shot noise gives rise to a spread in experimental outcomes that masks the uncertainty intrinsic to quantum theory. Taking inspiration from spin-echo protocols, we propose a decoupling technique that, under ideal conditions, perfectly cancels shot-to-shot force noise in squeezing experiments based on parametric modulation. We implement the protocol using an optically levitated nanoparticle, where shot-to-shot force noise arises from slowly varying stray fields acting on the charge carried by the particle. Using our oscillator-echo protocol, we demonstrate shot-to-shot noise suppression to the measurement-backaction limit.

quant-ph↗

arXiv2026

Nanomechanical sensor resolving impulsive forces below its zero-point fluctuations

The sensitivity of a mechanical transducer is ultimately limited by its inherent quantum fluctuations. Here, we use an optically levitated nanoparticle to measure impulsive forces smaller than the particle's zero-point momentum uncertainty. Our approach relies on reversibly squeezing the levitated particle's center-of-mass motion to coherently amplify the perturbation. We demonstrate resolving single impulsive-force kicks as small as 6.9 keV/c, a value 0.6 dB below the sensor's zero-point value.

quant-ph↗

arXiv2025

Shot-to-shot displacement noise in state-expansion protocols with inverted potentials

Optically levitated nanoparticles are promising candidates for the generation of macroscopic quantum states of mechanical motion. Protocols to generate such states expose the particle to a succession of different potentials. Limited reproducibility of the alignment of these potentials across experimental realizations introduces additional noise. Here, we experimentally investigate and model how such shot-to-shot noise limits the coherence length of a levitated nanoparticle during a state-expansion protocol using a dark, inverted electrical potential. We identify electric stray fields and mechanical instabilities as major sources of shot-to-shot fluctuations. We discuss the resulting experimental requirements for state expansion protocols exploiting inverted potentials.

quant-ph↗

arXiv2025

Trap-to-trap free falls with an optically levitated nanoparticle

We perform free-fall experiments with a charge-neutral, optically levitated nanoparticle. This is achieved using an optical tweezer that can be rapidly toggled on and off and vertically displaced, enabling the particle to be released and recaptured after each free fall. The particle is insensitive to electric fields due to its charge neutrality and, during free evolution, is not subject to photon recoil heating. We achieve free-fall durations of up to 0.25 ms and observe a nearly two hundred-fold increase in the particle's position uncertainty at recapture. The current limit on the free-fall time arises from the performance of the initial cooling step. By implementing linear feedback techniques and reducing the background pressure, we expect to perform millisecond-scale free-fall experiments in ultra-high vacuum, opening new opportunities for generating large delocalizations of levitated objects.

quant-ph↗

arXiv2024

High-purity quantum optomechanics at room temperature

Exploiting quantum effects of mechanical motion, such as backaction evading measurements or squeezing, requires preparation of the oscillator in a high-purity state. The largest state purities in optomechanics to date have relied on cryogenic cooling, combined with coupling to electromagnetic resonators driven with a coherent radiation field. In this work, we cool the mega-hertz-frequency librational mode of an optically levitated silica nanoparticle from room temperature to its quantum ground state. Cooling is realized by coherent scattering into a Fabry-Perot cavity. We use sideband thermometry to infer a phonon population of 0.04 quanta under optimal conditions, corresponding to a state purity of 92%. The purity reached by our room-temperature experiment exceeds the performance offered by mechanically clamped oscillators in a cryogenic environment. Our work establishes a platform for high-purity quantum optomechanics at room temperature.

quant-ph↗

arXiv2024

Motional entanglement of remote optically levitated nanoparticles

We show how to entangle the motion of optically levitated nanoparticles in distant optical tweezers. The scheme consists in coupling the inelastically scattered light of each particle into transmission lines and directing it towards the other particle. The interference between this light and the background field introduces an effective coupling between the two particles while simultaneously reducing the effect of recoil heating. We analyze the system dynamics, showing that both transient and conditional entanglement between remote particles can be achieved under realistic experimental conditions.

quant-ph↗

arXiv2024

Quantum Delocalization of a Levitated Nanoparticle

Every massive particle behaves like a wave, according to quantum physics. Yet, this characteristic wave nature has only been observed in double-slit experiments with microscopic systems, such as atoms and molecules. The key aspect is that the wavefunction describing the motion of these systems extends coherently over a distance comparable to the slit separation, much larger than the size of the system itself. Preparing these states of more massive and complex objects remains an outstanding challenge. While the motion of solid-state oscillators can now be controlled at the level of single quanta, their coherence length remains comparable to the zero-point motion, limited to subatomic distances. Here, we prepare a delocalized state of a levitating solid-state nanosphere with coherence length exceeding the zero-point motion. We first cool its motion to the ground state. Then, by modulating the stiffness of the confinement potential, we achieve more than a threefold increment of the initial coherence length with minimal added noise. Optical levitation gives us the necessary control over the confinement that other mechanical platforms lack. Our work is a stepping stone towards the generation of delocalization scales comparable to the object size, a crucial regime for macroscopic quantum experiments, and towards quantum-enhanced force sensing with levitated particles.

quant-ph↗

arXiv2024

Feedback cooling a levitated nanoparticle's libration to below 100 phonons

Macroscopic rotors are interesting model systems to test quantum theory and for quantum sensing. A promising approach for bringing these systems to the quantum regime is to combine sensitive detection with feedback cooling to reduce the thermal occupation of the mechanics. Here, we implement a backward-scattering scheme to efficiently detect all three libration modes of an optically levitated nanoparticle. We demonstrate parametric feedback cooling of all three libration degrees of freedom to below 16~mK, with one of the modes reaching the temperature of 1.3~mK, corresponding to a mean phonon number of 84. Finally, we characterize the backward-scattering scheme by determining its measurement efficiency to be 0.5\%.

quant-ph↗

arXiv2023

State Expansion of a Levitated Nanoparticle in a Dark Harmonic Potential

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.

quant-ph↗

arXiv2023

Hybrid Paul-optical trap with large optical access for levitated optomechanics

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.

quant-ph↗

arXiv2023

Spinning a levitated mechanical oscillator far into the deep-strong coupling regime

The field of levitodynamics has made substantial advancements in manipulating the translational and rotational degrees of freedom of levitated nanoparticles. Notably, rotational degrees of freedom can now be cooled to millikelvin temperatures and driven into GHz rotational speeds. However, in the case of cylindrically symmetric nanorotors, only the rotations around their short axes have been effectively manipulated, while the possibility to control rotation around the longer axis has remained a notable gap in the field. Here, we extend the rotational control toolbox by engineering an optically levitated nanodumbbell in vacuum into controlled spinning around its long axis with spinning rates exceeding 1 GHz. This fast spinning introduces deep-strong coupling between the nanodumbell's libration modes, such that the coupling rate $g$ exceeds the bare libration frequencies $Ω_0$ by two orders of magnitude with $g/Ω_0=724\pm 33$. Our control over the long-axis rotation opens the door to study the physics of deep-strong coupled mechanical oscillators and to observe macroscopic rotational quantum interference effects, thus laying a solid foundation for future applications in quantum technologies. Additionally, we find that our system offers great potential as a nanoscopic gyroscope with competitive sensitivity.

physics.optics↗

arXiv2023

Full control of the libration potential in rotational levitodynamics

Control of the potential energy and free evolution lie at the heart of levitodynamics as key requirements for sensing, wave function expansion, and mechanical squeezing protocols. Here, we experimentally demonstrate full control over the optical potential governing the librational degrees of freedom of a levitated anisotropic nanoparticle. This control is achieved by introducing the degree of polarization as a new tool for rotational levitodynamics. We demonstrate the free rotation of a levitated anisotropic scatterer around its short axis and and we use the rotational degrees of freedom to probe the local spin of a strongly focused laser beam.

physics.optics↗

arXiv2023

Surface-Sensitive Raman Scattering by Transferable Nanoporous Plasmonic Membranes

Raman spectroscopy is a powerful technique to characterize materials. It probes non-destructively chemical composition, crystallinity, defects, strain and coupling phenomena. However, the Raman response of surfaces or thin films is often weak and obscured by dominant bulk signals. Here we overcome this limitation by placing a transferable porous gold membrane (PAuM) on top of the surface of interest. Slot-like nanopores in the membrane act as plasmonic slot antennas and enhance the Raman response of the surface or thin film underneath. Simultaneously, the PAuM suppresses the penetration of the excitation laser into the bulk, efficiently blocking the bulk Raman signal. Using graphene as a model surface, we show that these two simultaneous effects lead to an increase in the surface-to-bulk Raman signal ratio by three orders of magnitude. We find that 90% of the Raman enhancement occurs within the top 2.5 of the material, demonstrating truly surface-sensitive Raman scattering. To validate our approach, we analyze the surface of a LaNiO3 thin film. We observe a Raman mode splitting for the LaNiO3 surface-layer, which is spectroscopic evidence that the surface structure differs from the bulk. This result underpins that PAuM give direct access to Raman signatures of surfaces and their structural properties.

cond-mat.mtrl-sci↗

arXiv2022

Optomechanical sideband asymmetry explained by stochastic electrodynamics

Within the framework of stochastic electrodynamics we derive the noise spectrum of a laser beam reflected from a suspended mirror. The electromagnetic field follows Maxwell's equations and is described by a deterministic part that accounts for the laser field and a stochastic part that accounts for thermal and zero-point background fluctuations.Likewise, the mirror motion satisfies Newton's equation of motion and is composed of deterministic and stochastic parts, similar to a Langevin equation. We consider a photodetector that records the power of the field reflected from the mirror interfering with a frequency-shifted reference beam (heterodyne interferometry). We theoretically show that the power spectral density of the photodetector signal is composed of four parts: (i) a deterministic term with beat notes, (ii) shot noise, (iii) the actual heterodyne signal of the mirror motion and (iv) a cross term resulting from the correlation between measurement noise (shot noise) and backaction noise (radiation pressure shot noise). The latter gives rise to the Raman sideband asymmetry observed with ultracold atoms, cavity optomechanics and with levitated nanoparticles. Our classical theory fully reproduces experimental observations and agrees with the results obtained by a quantum theoretical treatment.

quant-ph↗

arXiv2022

White-noise fluctuation theorem for Langevin dynamics

Fluctuation theorems based on time-reversal have provided remarkable insight into the non-equilibrium statistics of thermodynamic quantities like heat, work, and entropy production. These types of laws impose constraints on the distributions of certain trajectory functionals that reflect underlying dynamical symmetries. In this work, we introduce a detailed fluctuation theorem for Langevin dynamics that follows from the statistics of Gaussian white noise rather than from time-reversal. The theorem, which originates from a point-wise symmetry in phase space, holds individually for each degree of freedom coupled to additive or multiplicative noise. The relation is independent of the phase space distribution generated by the dynamics and can be used to derive a versatile parameter inference algorithm applicable to the a wide range of systems, including non-conservative and non-Markovian ones.

cond-mat.stat-mech↗

arXiv2022

Encoding information in the mutual coherence of spatially separated light beams

Coherence has been used as a resource for optical communications since its earliest days. It is widely used for multiplexing of data, but not for encoding of data. Here we introduce a coding scheme, which we call \textit{mutual coherence coding}, to encode information in the mutual coherence of spatially separated light beams. We describe its implementation and analyze its performance by deriving the relevant figures of merit (signal-to-noise ratio, maximum bit-rate, and spectral efficiency) with respect to the number of transmitted beams. Mutual coherence coding yields a quadratic scaling of the number of transmitted signals with the number of employed light beams, which might have benefits for cryptography and data security.

physics.optics↗

arXiv2022

Scalable all-optical cold damping of levitated nanoparticles

The field of levitodynamics has made significant progress towards controlling and studying the motion of a levitated nanoparticle. Motional control relies on either autonomous feedback via a cavity or measurement-based feedback via external forces. Recent demonstrations of measurement-based ground-state cooling of a single nanoparticle employ linear velocity feedback, also called cold damping, and require the use of electrostatic forces on charged particles via external electrodes. Here we introduce a novel all-optical cold damping scheme based on spatial modulation of the trap position that is scalable to multiple particles. The scheme relies on using programmable optical tweezers to provide full independent control over trap frequency and position of each tweezer. We show that the technique cools the center-of-mass motion of particles down to $17\,$mK at a pressure of $2 \times 10^{-6}\,$mbar and demonstrate its scalability by simultaneously cooling the motion of two particles. Our work paves the way towards studying quantum interactions between particles, achieving 3D quantum control of particle motion without cavity-based cooling, electrodes or charged particles, and probing multipartite entanglement in levitated optomechanical systems.

physics.optics↗