Multiparameter optimisation of a magneto-optical trap using deep learning.

Machine learning based on artificial neural networks has emerged as an efficient means to develop empirical models of complex systems. Cold atomic ensembles have become commonplace in laboratories around the world, however, many-body interactions give rise to complex dynamics that preclude precise analytic optimisation of the cooling and trapping process. Here, we implement a deep artificial neural network to optimise the magneto-optic cooling and trapping of neutral atomic ensembles. The solution identified by machine learning is radically different to the smoothly varying adiabatic solutions currently used. Despite this, the solutions outperform best known solutions producing higher optical densities.

Ultranarrow Optical Inhomogeneous Linewidth in a Stoichiometric Rare-Earth Crystal.

We obtain a low optical inhomogeneous linewidth of 25 MHz in the stoichiometric rare-earth crystal EuCl_{3}·6H_{2}O by isotopically purifying the crystal in ^{35}Cl. With this linewidth, an important limit for stoichiometric rare-earth crystals is surpassed: the hyperfine structure of ^{153}Eu is spectrally resolved, allowing the whole population of ^{153}Eu^{3+} ions to be prepared in the same hyperfine state using hole-burning techniques. This material also has a very high optical density, and can have long coherence times when deuterated. This combination of properties offers new prospects for quantum information applications. We consider two of these: quantum memories and quantum many-body studies. We detail the improvements in the performance of current memory protocols possible in these high optical depth crystals, and describe how certain memory protocols, such as off-resonant Raman memories, can be implemented for the first time in a solid-state system. We explain how the strong excitation-induced interactions observed in this material resemble those seen in Rydberg systems, and describe how these interactions can lead to quantum many-body states that could be observed using standard optical spectroscopy techniques.

Non-destructive shadowgraph imaging of ultra-cold atoms.

An imaging system is presented that is capable of far-detuned non-destructive imaging of a Bose-Einstein condensate with the signal proportional to the second spatial derivative of the density. Whilst demonstrated with application to Rb85, the technique generalizes to other atomic species and is shown to be capable of a signal-to-noise of ∼25 at 1 GHz detuning with 100 in-trap images showing no observable heating or atom loss. The technique is also applied to the observation of individual trajectories of stochastic dynamics inaccessible to single shot imaging. Coupled with a fast optical phase locked loop, the system is capable of dynamically switching to resonant absorption imaging during the experiment.

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

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.

Sagnac Interferometry with a Single Atomic Clock.

The Sagnac effect enables interferometric measurements of rotation with high precision. Using matter waves instead of light promises resolution enhancement by orders of magnitude that scales with particle mass. So far, the paradigm for matter wave Sagnac interferometry relies on de Broglie waves and thus on free propagation of atoms either in free fall or within waveguides. However, the Sagnac effect can be expressed as a proper time difference experienced by two observers moving in opposite directions along closed paths and has indeed been measured with atomic clocks flown around Earth. Inspired by this, we investigate an interferometer comprised of a single atomic clock. The Sagnac effect manifests as a phase shift between trapped atoms in different internal states after transportation along closed paths in opposite directions, without any free propagation. With analytic models, we quantify limitations of the scheme arising from atomic dynamics and finite temperature. Furthermore, we suggest an implementation with previously demonstrated technology.

Bone marrow transplantation for patients with Fanconi anemia: a study of 24 cases from a single institution.

Although bone marrow transplantation (BMT) can eliminate the hematologic manifestations of Fanconi anemia (FA), patients are unusually susceptible to complications associated with the use of cyclophosphamide (CY) in the conditioning regimen. To investigate modifications of the conditioning regimen, we reviewed the records of 24 patients with FA who received an allogeneic BMT. All patients presented with severe pancytopenia. One patient was transplanted with overt leukemia as well. Donors were HLA-identical siblings in 22 cases and 1- and 2-antigen mismatched relatives in two cases, respectively. All conditioning regimens included CY 200 mg/kg in 10 patients; 140 mg/kg with or without antithymocyte globulin in 12 and 20 mg/kg with 400 cGy total body irradiation in two. GVHD prophylaxis comprised methotrexate and/or cyclosporine. Only one of 21 evaluable patients did not show signs of engraftment. Toxicities included grade III/IV mucositis in 20 patients, severe dermatitis in four and veno-occlusive disease in four. Acute GVHD (> or = grade II) occurred in nine of 22 patients. Four patients developed chronic GVHD. With a median follow-up time of 24 months, 14 of the 24 patients are alive with normal hematopoietic function. Eight of the 10 patients with matched sibling donors who were conditioned with CY 140 mg/kg are alive and well. We conclude that BMT is an effective treatment for FA. Conditioning regimens using lower doses of CY are associated with manageable toxicity and can potentially increase the survival rate of patients with HLA-matched donors.