Vacuum levitation and motion control on chip.

By isolating from the environment and precisely controlling mesoscopic objects, levitation in vacuum has evolved into a versatile technique that has already benefited diverse scientific directions, from force sensing and thermodynamics to materials science and chemistry. It also holds great promise for advancing the study of quantum mechanics in the unexplored macroscopic regime. However, most current levitation platforms are complex and bulky.

Levitated Optomechanics with Meta-Atoms.

We propose to introduce additional control in levitated optomechanics by trapping a meta-atom, i.e., a subwavelength and high-permittivity dielectric particle supporting Mie resonances.

Ultrathin Tunable Optomechanical Metalens.

Reconfigurable metasurfaces offer great promises to enhance photonics technology by combining integration with improved functionalities. Recently, reconfigurability in otherwise static metasurfaces has been achieved by modifying the electric permittivity of the meta-atoms themselves or their immediate surrounding. Yet, it remains challenging to achieve significant and fast tunability without increasing bulkiness.

Precision Calibration of the Duffing Oscillator with Phase Control.

The Duffing oscillator is a nonlinear extension of the ubiquitous harmonic oscillator and as such plays an outstanding role in science and technology. Experimentally, the system parameters are determined by a measurement of its response to an external excitation. When changing the amplitude or frequency of the external excitation, a sudden jump in the response function reveals the nonlinear dynamics prominently.

A Chemical Nanoreactor Based on a Levitated Nanoparticle in Vacuum.

A single levitated nanoparticle is used as a nanoreactor for studying surface chemistry at the nanoscale. Optical levitation under controlled pressure, surrounding gas composition, and humidity provides extreme control over the nanoparticle, including dynamics, charge, and surface chemistry. Using a single nanoparticle avoids ensemble averages and allows studying how the presence of silanol groups at its surface affects the adsorption and desorption of water from the background gas with excellent spatial and temporal resolution.

Mechanical Squeezing via Unstable Dynamics in a Microcavity.

We theoretically show that strong mechanical quantum squeezing in a linear optomechanical system can be rapidly generated through the dynamical instability reached in the far red-detuned and ultrastrong coupling regime. We show that this mechanism, which harnesses unstable multimode quantum dynamics, is particularly suited to levitated optomechanics, and we argue for its feasibility for the case of a levitated nanoparticle coupled to a microcavity via coherent scattering. We predict that for submillimeter-sized cavities the particle motion, initially thermal and well above its ground state, becomes mechanically squeezed by tens of decibels on a microsecond timescale.

Strong optomechanical coupling at room temperature by coherent scattering.

Quantum control of a system requires the manipulation of quantum states faster than any decoherence rate. For mesoscopic systems, this has so far only been reached by few cryogenic systems. An important milestone towards quantum control is the so-called strong coupling regime, which in cavity optomechanics corresponds to an optomechanical coupling strength larger than cavity decay rate and mechanical damping.

Resolved-Sideband Cooling of a Levitated Nanoparticle in the Presence of Laser Phase Noise.

We investigate the influence of laser phase noise heating on resolved sideband cooling in the context of cooling the center-of-mass motion of a levitated nanoparticle in a high-finesse cavity. Although phase noise heating is not a fundamental physical constraint, the regime where it becomes the main limitation in Levitodynamics has so far been unexplored and hence embodies from this point forward the main obstacle in reaching the motional ground state of levitated mesoscopic objects with resolved sideband cooling. We reach minimal center-of-mass temperatures comparable to T_{min}=10  mK at a pressure of p=3×10^{-7}  mbar, solely limited by phase noise.

Optimal Feedback Cooling of a Charged Levitated Nanoparticle with Adaptive Control.

We use an optimal control protocol to cool one mode of the center-of-mass motion of an optically levitated nanoparticle. The feedback technique relies on exerting a Coulomb force on a charged particle with a pair of electrodes and follows the control law of a linear quadratic regulator, whose gains are optimized by a machine learning algorithm in under 5 s. With a simpler and more robust setup than optical feedback schemes, we achieve a minimum center-of-mass temperature of 5 mK at 3×10^{-7}  mbar and transients 10-600 times faster than cold damping.

Observation of Two-Dimensional Localized Jones-Roberts Solitons in Bose-Einstein Condensates.

Jones-Roberts solitons are the only known class of stable dark solitonic solutions of the nonlinear Schrödinger equation in two and three dimensions. They feature a distinctive elongated elliptical shape that allows them to travel without change of form. By imprinting a triangular phase pattern, we experimentally generate two-dimensional Jones-Roberts solitons in a three-dimensional atomic Bose-Einstein condensate.

[μ-1,1'-Bis(diphenyl-phosphino)ferro-cene-κP:P']bis-[chloridogold(I)]-chloro-form-hexane (2/2/1).

In the title mixed solvate, [Au(2)Fe(C(17)H(14)P)(2)Cl(2)]·CHCl(3)·0.5CH(3)(CH(2))(4)CH(3), the hexane solvent mol-ecule is disposed about an inversion centre. The Au atoms exist within nearly ideal linear coordination defined by P,Cl-donor sets, and when viewed down the P⋯P axis the Au atoms are gauche to each other.

The contributions of encoding, retention, and recall to the Hebb effect.

The article reports an experiment testing whether the Hebb repetition effect-the gradual improvement of immediate serial recall when the same list is repeated several times-depends on overt recall of the repeated lists. Previous reports which suggest that recall is critical confound the recall manipulation with retention interval. The present experiment orthogonally varies retention interval (0 or 9 s) and whether the list is to be recalled after the retention interval.

Establishment of hapten-specific monoclonal avian IgY by conversion of antibody fragments obtained from combinatorial libraries.

Nowadays, recombinant antibody and phage display technology enable the efficient generation of immunotools and a subsequent manipulation for optimized affinity, specificity or overall performance. Such advantages are of particular interest for haptenic target structures, such as TNT (2,4,6-trinitrotoluene). The toxicity of TNT and its breakdown products makes a reliable and fast detection of low levels in aqueous samples highly important.

Strain-specific susceptibility for neurodegeneration in a rat model of autoimmune optic neuritis.

Heterogeneity in clinical disease course and histopathology complicates the treatment of multiple sclerosis. We detected important differences in neurodegeneration in various subtypes of myelin oligodendrocyte glycoprotein (MOG)-induced optic neuritis. Dark Agouti (DA) rats showed a significantly higher survival of retinal ganglion cells in comparison to Brown Norway rats.

Human guanylate binding protein-1 is a secreted GTPase present in increased concentrations in the cerebrospinal fluid of patients with bacterial meningitis.

Interferon-gamma-induced GTPases are key to the protective immunity against microbial and viral pathogens. As yet, the cell interior has been regarded as the exclusive residence of these proteins. Here we show that a member of this group, human guanylate binding protein-1 (hGBP-1), is secreted from cells.