Integration of a high finesse cryogenic build-up cavity with an ion trap.

We report on the realization of a hemispherical optical cavity with a finesse of F = 13 000 and sustaining inter-cavity powers of 10 kW, which we operate in a closed-cycle cryostat vacuum system close to 4 K. This was designed and built with an integrated radio-frequency Paul trap in order to combine optical and radio-frequency trapping. The cavity provides a power build-up factor of 2300. We describe a number of aspects of the system's design and operation, including low-vibration mounting and locking and thermal effects at high powers. Thermal self-locking in the high intracavity power regime was observed to enhance passive stability below 1 kHz. Observations made over repeated cool-downs over the course of a year show a repeatable shift between the ion trap center and the cavity mode.

Experimental Constraint on Axionlike Particles over Seven Orders of Magnitude in Mass.

We use our recent electric dipole moment (EDM) measurement data to constrain the possibility that the HfF^{+} EDM oscillates in time due to interactions with candidate dark matter axionlike particles (ALPs). We employ a Bayesian analysis method which accounts for both the look-elsewhere effect and the uncertainties associated with stochastic density fluctuations in the ALP field. We find no evidence of an oscillating EDM over a range spanning from 27 nHz to 400 mHz, and we use this result to constrain the ALP-gluon coupling over the mass range 10^{-22}-10^{-15} eV. This is the first laboratory constraint on the ALP-gluon coupling in the 10^{-17}-10^{-15} eV range, and the first laboratory constraint to properly account for the stochastic nature of the ALP field.

Predictive models using "cheap and easy" field measurements: Can they fill a gap in planning, monitoring, and implementing fecal sludge management solutions?

The characteristics of fecal sludge delivered to treatment plants are highly variable. Adapting treatment process operations accordingly is challenging due to a lack of analytical capacity for characterization and monitoring at many treatment plants. Cost-efficient and simple field measurements such as photographs and probe readings could be proxies for process control parameters that normally require laboratory analysis. To investigate this, we evaluated questionnaire data, expert assessments, and simple analytical measurements for fecal sludge collected from 421 onsite containments. This data served as inputs to models of varying complexity. Random forest and linear regression models were able to predict physical-chemical characteristics including total solids (TS) and ammonium (NH4+-N) concentrations, and solid-liquid separation performance including settling efficiency and filtration time (R2 from 0.51-0.66) based on image analysis of photographs (sludge color, supernatant color, and texture) and probe readings (conductivity (EC) and pH). Supernatant color was the best predictor of settling efficiency and filtration time, EC was the best predictor of NH4+-N, and texture was the best predictor of TS. Predictive models have the potential to be applied for real-time monitoring and process control if a database of measurements is developed and models are validated in other cities. Simple decision tree models based on the single classifier of containment type can also be used to make predictions about citywide planning, where a lower degree of accuracy is required.

Precision Measurement of the Electron's Electric Dipole Moment Using Trapped Molecular Ions.

We describe the first precision measurement of the electron's electric dipole moment (d_{e}) using trapped molecular ions, demonstrating the application of spin interrogation times over 700 ms to achieve high sensitivity and stringent rejection of systematic errors. Through electron spin resonance spectroscopy on ^{180}Hf^{19}F^{+} in its metastable ^{3}Δ_{1} electronic state, we obtain d_{e}=(0.9±7.7_{stat}±1.7_{syst})×10^{-29} e cm, resulting in an upper bound of |d_{e}|<1.3×10^{-28} e cm (90% confidence). Our result provides independent confirmation of the current upper bound of |d_{e}|<9.4×10^{-29} e cm [J. Baron et al., New J. Phys. 19, 073029 (2017)NJOPFM1367-263010.1088/1367-2630/aa708e], and offers the potential to improve on this limit in the near future.

Phase synchronization of two anharmonic nanomechanical oscillators.

We investigate the synchronization of oscillators based on anharmonic nanoelectromechanical resonators. Our experimental implementation allows unprecedented observation and control of parameters governing the dynamics of synchronization. We find close quantitative agreement between experimental data and theory describing reactively coupled Duffing resonators with fully saturated feedback gain. In the synchronized state we demonstrate a significant reduction in the phase noise of the oscillators, which is key for sensor and clock applications. Our work establishes that oscillator networks constructed from nanomechanical resonators form an ideal laboratory to study synchronization--given their high-quality factors, small footprint, and ease of cointegration with modern electronic signal processing technologies.

Laser-induced fluorescence studies of HfF+ produced by autoionization.

Autoionization of Rydberg states of HfF, prepared using the optical-optical double resonance technique, holds promise to create HfF(+) in a particular Zeeman level of a rovibronic state for an electron electric dipole moment search. We characterize a vibronic band of Rydberg HfF at 54 cm(-1) above the lowest ionization threshold and directly probe the state of the ions formed from this vibronic band by performing laser-induced fluorescence on the ions. The Rydberg HfF molecules show a propensity to decay into only a few ion rotational states of a given parity and are found to preserve their orientation qualitatively upon autoionization. We show empirically that we can create 30% of the total ion yield in a particular ∣J(+), M(+) state and present a simplified model describing autoionization from a given Rydberg state that assumes no angular dynamics.