Kyle S. Hardman

Precision atomic gravimeter based on Bragg diffraction

We present a precision gravimeter based on coherent Bragg diffraction of freely falling cold atoms. Traditionally, atomic gravimeters have used stimulated Raman transitions to separate clouds in momentum space by driving transitions between two internal atomic states. Bragg interferometers utilize only a single internal state, and can therefore be less susceptible to environmental perturbations. Here we show that atoms extracted from a magneto-optical trap using an accelerating optical lattice are a suitable source for a Bragg atom interferometer, allowing efficient beamsplitting and subsequent separation of momentum states for detection. Despite the inherently multi-state nature of atom diffraction, we are able to build a Mach-Zehnder interferometer using Bragg scattering which achieves a sensitivity to the gravitational acceleration of Δg/g = 2.7 × 10-9 with an integration time of 1000 s. The device can also be converted to a gravity gradiometer by a simple modification of the light pulse sequence.

Bright solitonic matter-wave interferometer.

We present the first realization of a solitonic atom interferometer. A Bose-Einstein condensate of 1×10(4) atoms of rubidium-85 is loaded into a horizontal optical waveguide. Through the use of a Feshbach resonance, the s-wave scattering length of the 85Rb atoms is tuned to a small negative value. This attractive atomic interaction then balances the inherent matter-wave dispersion, creating a bright solitonic matter wave. A Mach-Zehnder interferometer is constructed by driving Bragg transitions with the use of an optical lattice colinear with the waveguide. Matter-wave propagation and interferometric fringe visibility are compared across a range of s-wave scattering values including repulsive, attractive and noninteracting values. The solitonic matter wave is found to significantly increase fringe visibility even compared with a noninteracting cloud.

80hk momentum separation with Bloch oscillations in an optically guided atom interferometer

We demonstrate phase sensitivity in a horizontally guided, acceleration-sensitive atom interferometer with a momentum separation of

Fast machine-learning online optimization of ultra-cold-atom experiments.

80\ensuremath{\hbar}k

Simultaneous Precision Gravimetry and Magnetic Gradiometry with a Bose-Einstein Condensate: A High Precision, Quantum Sensor

between its arms. A fringe visibility of 7% is observed. Our coherent pulse sequence accelerates the cold cloud in an optical waveguide, an inherently scalable route to large momentum separation and high sensitivity. We maintain coherence at high momentum separation due to both the transverse confinement provided by the guide and our use of optical

External cavity diode lasers with 5kHz linewidth and 200nm tuning range at 1.55μm and methods for linewidth measurement

\ensuremath{\delta}

Optically guided linear Mach-Zehnder atom interferometer

-kick cooling on our cold-atom cloud. We also construct a horizontal interferometric gradiometer to measure the longitudinal curvature of our optical waveguide.

A Bose-condensed, simultaneous dual-species Mach?Zehnder atom interferometer

We apply an online optimization process based on machine learning to the production of Bose-Einstein condensates (BEC). BEC is typically created with an exponential evaporation ramp that is optimal for ergodic dynamics with two-body s-wave interactions and no other loss rates, but likely sub-optimal for real experiments. Through repeated machine-controlled scientific experimentation and observations our ‘learner’ discovers an optimal evaporation ramp for BEC production. In contrast to previous work, our learner uses a Gaussian process to develop a statistical model of the relationship between the parameters it controls and the quality of the BEC produced. We demonstrate that the Gaussian process machine learner is able to discover a ramp that produces high quality BECs in 10 times fewer iterations than a previously used online optimization technique. Furthermore, we show the internal model developed can be used to determine which parameters are essential in BEC creation and which are unimportant, providing insight into the optimization process of the system.

Observation of a modulational instability in Bose-Einstein condensates

A Bose-Einstein condensate is used as an atomic source for a high precision sensor. A 5 × 10 atom F=1 spinor condensate of Rb is released into free fall for up to 750 ms and probed with a T = 130 ms Mach-Zehnder atom interferometer based on Bragg transitions. The Bragg interferometer simultaneously addresses the three magnetic states, |mf = 1, 0,−1〉, facilitating a simultaneous measurement of the acceleration due to gravity with a 1000 run precision of ∆g/g= 1.45× 10−9 and the magnetic field gradient to a precision 120 pT/m.

A faster scaling in acceleration-sensitive atom interferometers

Two simple external cavity diode laser designs using fibre pigtailed gain chips are tested and their properties compared with a high end DBR fibre laser. These ECDLs demonstrate a FWHM linewidth as low as 5.2kHz with a fitted Lorentzian FWHM linewidth as low as 1.6kHz. Tuning ranges of 200nm covering 1420nm to 1620nm were demonstrated. To the best of our knowledge these are the narrowest linewidth and most broadly tunable external cavity diode lasers reported to date. The improvement in linewidth is attributed to greatly enhanced acoustic isolation allowed by using fiber coupled gain chips and by replacing kinematic mounts with a pair of rotatable wedges for cavity alignment which eliminates acoustic resonances. A detailed description and discussion of techniques used to characterize the frequency noise and linewidths of these lasers is provided.