Quantum-enhanced sensing of a single-ion mechanical oscillator.

Special quantum states are used in metrology to achieve sensitivities below the limits established by classically behaving states1,2. In bosonic interferometers, squeezed states3, number states4,5 and 'Schrödinger cat' states5 have been implemented on various platforms and have demonstrated improved measurement precision over interferometers using coherent states6,7. Another metrologically useful state is an equal superposition of two eigenstates with maximally different energies; this state ideally reaches the full interferometric sensitivity allowed by quantum mechanics8,9. Here we demonstrate the enhanced sensitivity of these quantum states in the case of a harmonic oscillator. We extend an existing experimental technique10 to create number states of order up to n = 100 and to generate superpositions of a harmonic oscillator ground state and a number state of the form [Formula: see text] with n up to 18 in the motion of a single trapped ion. Although experimental imperfections prevent us from reaching the ideal Heisenberg limit, we observe enhanced sensitivity to changes in the frequency of the mechanical oscillator. This sensitivity initially increases linearly with n and reaches a maximum at n = 12, where we observe a metrological enhancement of 6.4(4) decibels (the uncertainty is one standard deviation of the mean) compared to an ideal measurement on a coherent state with the same average occupation number. Such measurements should provide improved characterization of motional decoherence, which is an important source of error in quantum information processing with trapped ions11,12. It should also be possible to use the quantum advantage from number-state superpositions to achieve precision measurements in other harmonic oscillator systems.

Quantum Harmonic Oscillator Spectrum Analyzers.

Characterization and suppression of noise are essential for the control of harmonic oscillators in the quantum regime. We measure the noise spectrum of a quantum harmonic oscillator from low frequency to near the oscillator resonance by sensing its response to amplitude modulated periodic drives with a qubit. Using the motion of a trapped ion, we experimentally demonstrate two different implementations with combined sensitivity to noise from 500 Hz to 600 kHz. We apply our method to measure the intrinsic noise spectrum of an ion trap potential in a previously unaccessed frequency range.

In Situ RheoNMR Correlation of Polymer Segmental Mobility with Mechanical Properties during Hydrogel Synthesis.

Understanding polymer gelation over multiple length-scales is crucial to develop advanced materials. An experimental setup is developed that combines rheological measurements with simultaneous time-domain 1 H NMR relaxometry (TD-NMR) techniques, which are used to study molecular motion (<10 nm) in soft matter. This so-called low-field RheoNMR setup is used to study the impact of varying degrees of crosslinking (DC) on the gelation kinetics of acrylic acid (AAc) and N,N'-methylene bisacrylamide (MBA) free radical crosslinking copolymerization. A stretched exponential function describes the T2 relaxation curves throughout the gelation process. The stretching exponent ß decreases from 0.90 to 0.67 as a function of increasing DC, suggesting an increase in network heterogeneity with a broad T2 distribution at higher DC. The inverse correlation of the elastic modulus G' with T2 relaxation times reveals a pronounced molecular rigidity for higher DC at early gelation times, indicating the formation of inelastic, rigid domains such as crosslinking clusters. The authors further correlate G' with the polymer concentration during gelation using a T1 filter for solvent suppression. A characteristic scaling exponent of 2.3 is found, which is in agreement with theoretical predictions of G' based on the confining tube model in semi-dilute entangled polymer solutions.

Safety, Effect and Feasibility of Percutaneous SI-Screw with and without Augmentation-A 15-Year Retrospective Analysis on over 640 Screws.

BACKGROUND: Minimally invasive sacroiliac-screw (SI-screw) fixation of the pelvis is used in energy trauma (Arbeitsgemeinschaft für Osteosynthesefragen (AO) classified) and fragility fractures (Fragility Fracture of the Pelvis (FFP) classified). However, available clinical data are based on small case series and biomechanical data seem to be contradictory. METHODS: The present single center retrospective cohort study investigated percutaneous SI-screw fixation and augmentation over 15 years. Groups were compared concerning the general epidemiological data, mobilization, complication rates, duration of stay, and safety of SI-screw insertion. Multivariable analyses were performed using logistic regression. RESULTS: Between 2005 and March 2020, 448 patients with 642 inserted SI-screws were identified. Iatrogenic neurological impairment was documented in 2.47% and correlated with screw misplacement. There was an increased complication risk in patients with AO type C over patients with AO type B and in FFP II over FFP III/IV patients. Cement-augmented FFP patients showed a 25% reduced stay in hospital and a reduced complication risk. Cement-associated complications were seen in 22% without correlation to neurologic impairment. CONCLUSIONS: The present study confirms the safety and usability of percutaneous SI-screw fixation, despite specific risks. Cement augmentation seems to reduce the complication risk in FFP patients and shorten hospital stay for some reasons, without increased specific complications or correlated neurological impairment.

Do wearable alcohol-based handrub dispensers increase hand hygiene compliance? - a mixed-methods study.

Background: Hand Hygiene (HH) compliance was shown to be poor in several studies. Improving the availability of alcohol-based hand rub (ABHR) is a cornerstone for increasing HH compliance. Methods: In this study, we introduced wearable dispensers for ABHR in an Emergency Department (ED) well equipped with mounted ABHR dispensers and accompanied this single-modal intervention by a quasi-experimental mixed-method study. The study was performed in the ED of the University Hospital Zurich, Switzerland, a 950-bed tertiary teaching hospital. During a five-week baseline period and a seven-week intervention period, we observed HH compliance according to the WHO 'Five Moments' concept, measured ABHR consumption, and investigated perceived ABHR availability, self-reported HH compliance and knowledge of HH indications by questionnaire. Multivariable logistic regression was used to identify independent determinants for HH compliance. In addition, semi-structured interviews were conducted and thematically analyzed to assess barriers and facilitators for the use of the newly introduced dispensers. Results: Across 811 observed HH opportunities, the HH compliance for all moments was 56% (95% confidence interval (CI), 51-62%) during baseline and 64% (CI, 59-68%) during intervention period, respectively. In the multivariable analysis adjusted for sex, profession, and WHO HH moment, there was no difference in HH compliance between baseline and intervention (adjusted Odds ratio: 1.22 (0.89-1.66), p = 0.22), No significant changes were observed in consumption and perceived availability of ABHR. During intervention, 7.5% ABHR was consumed using wearable dispensers. HCP perceived wearable dispensers as unnecessary since mounted dispensers were readily accessible. Poor ergonomic design of the wearable dispenser emerged as a main barrier, especially its lid and fastening mechanism. Interviewees identified two ideal situations for wearable dispensers, HCP who accompany patients from ED to other wards, and HCP approaching a patient from a non-patient areas in the ED such as the central working station or the meeting room. Conclusion: The introduction of wearable dispensers did not increase observed hand hygiene compliance or ABHR consumption in an ED already well equipped with mounted dispensers. For broader acceptance and use, wearable dispensers might benefit from an optimized ergonomic design.

Note: An avalanche transistor-based nanosecond pulse generator with 25 MHz repetition rate.

We have developed an avalanche transistor-based pulse generator for driving the photocathode of an image intensifier, which comprises a mainly capacitive load on the order of 100 pF. The circuit produces flat-top pulses with a rise time of 2 ns, a FWHM of 10 ns, and an amplitude of tens of V at a high repetition rate in the range of tens of MHz. The generator is built of identical avalanche transistor sections connected in parallel and triggered in a sequence, synchronized to a reference rf signal. The described circuit and mode of operation overcome the power dissipation limit of avalanche transistor generators and enable a significant increase of pulse repetition rates. Our approach is naturally suited for synchronized imaging applications at low light levels.