Measuring the Edwards-Anderson order parameter of the Bose glass : a quantum gas microscope approach

We thank D Cassettari, A Daley, S Denny, J Keeling, P Kirton and A Trombettoni for insightful discussions and assistance. Computations were performed on the EPSRC CDT Computer Cluster and the University of St Andrews School of Physics & Astronomy computer cluster. SJT acknowledges studentship funding from EPSRC under grant no. EP/G03673X/1. GDB acknowledges support from the Leverhulme Trust RPG-2013-074.With the advent of spatially resolved fluorescence imaging in quantum gas microscopes, it is now possible to directly image glassy phases and probe the local effects of disorder in a highly controllable setup. Here we present numerical calculations using a spatially resolved local mean-field theory, show that it captures the essential physics of the disordered system and use it to simulate the density distributions seen in single-shot fluorescence microscopy. From these simulated images we extract local properties of the phases which are measurable by a quantum gas microscope and show that unambiguous detection of the Bose glass is possible. In particular, we show that experimental determination of the Edwards-Anderson order parameter is possible in a strongly correlated quantum system using existing experiments. We also suggest modifications to the experiments which will allow further properties of the Bose glass to be measured.PostprintPeer reviewe

Can quantum gas microscopes directly image exotic glassy phases?

With the advent of spatially resolved fluorescence imaging in quantum gas microscopes (see e.g. [1]), it is now possible to directly image glassy phases and probe the local effects of disorder in a highly controllable setup. Here we present numerical calculations using a spatially resolved local mean-field theory, show that it captures the essential physics of the disordered system, and use it to simulate the density distributions seen in single-shot fluorescence microscopy [2]. From these simulated images we extract local properties of the phases which are measurable by a quantum gas microscope and show that unambiguous detection of the Bose glass is possible. In particular, we show that experimental determination of the Edwards-Anderson order parameter is possible in a strongly correlated quantum system using existing experiments. We also suggest modifications to the experiments by using spatial light modulators (see [3] and references therein) to tailor the lattice, which will allow further properties of the Bose glass to be measured. References: [1] E Haller, et al., "Single-atom imaging of fermions in a quantum-gas microscope" Nature Physics 11, 738 (2015) [2] S J Thomson, et al., "Measuring the Edwards-Anderson order parameter of the Bose glass: A quantum gas microscope approach" Phys. Rev. A 94, 051601(R) (2016) [3] F Buccheri, et al., "Holographic optical traps for atom-based topological Kondo devices" New J. Phys. 18, 075012 (2016)PostprintNon peer reviewe

Probing multiple-frequency atom-photon interactions with ultracold atoms

We dress atoms with multiple-radiofrequency fields and investigate the spectrum of transitions driven by an additional probe field. A complete theoretical description of this rich spectrum is presented, in which we find allowed transitions and determine their amplitudes using the resolvent formalism. Experimentally, we observe transitions up to sixth order in the probe field using radiofrequency spectroscopy of Bose-Einstein condensates trapped in single- and multiple-radiofrequency-dressed potentials. We find excellent agreement between theory and experiment, including the prediction and verification of previously unobserved transitions, even in the single-radiofrequency case.Comment: 20 pages, 7 figure

High-fidelity phase and amplitude control of phase-only computer generated holograms using conjugate gradient minimisation

Funding: Leverhulme Trust (RPG-2013-074); EPSRC (EP/G03673X/1; EP/L015110/1).We demonstrate simultaneous control of both the phase and amplitude of light using a conjugate gradient minimisation-based hologram calculation technique and a single phase-only spatial light modulator (SLM). A cost function, which incorporates the inner product of the light field with a chosen target field within a defined measure region, is efficiently minimised to create high fidelity patterns in the Fourier plane of the SLM. A fidelity of F = 0.999997 is achieved for a pattern resembling an LG01 mode with a calculated light-usage efficiency of 41.5%. Possible applications of our method in optical trapping and ultracold atoms are presented and we show uncorrected experimental realisation of our patterns with F = 0.97 and 7.8% light efficiency.Publisher PDFPeer reviewe

Inelastic collisions in radiofrequency-dressed mixtures of ultracold atoms

Radiofrequency (rf) -dressed potentials are a promising technique for manipulating atomic mixtures, but so far little work has been undertaken to understand the collisions of atoms held within these traps. In this paper, we dress a mixture of 85Rb and 87Rb with rf radiation, characterize the inelastic loss that occurs, and demonstrate species-selective manipulations. Our measurements show the loss is caused by two-body 87Rb+85Rb collisions, and we show the inelastic rate coefficient varies with detuning from the rf resonance. We explain our observations using quantum scattering calculations, which give reasonable agreement with the measurements. The calculations consider magnetic fields both perpendicular to the plane of rf polarization and tilted with respect to it. Our findings have important consequences for future experiments that dress mixtures with rf fields

Data underpinning High-fidelity phase and amplitude control of phase-only computer generated holograms using conjugate gradient minimisation

Data underpinning: D. Bowman, T. L. Harte, V. Chardonnet, C. De Groot, S. J. Denny, G. Le Goc, M. Anderson, P. Ireland, D. Cassettari, & G. D. Bruce, "High-fidelity phase and amplitude control of phase-only computer generated holograms using conjugate gradient minimisation" Opt. Express 25, 11692-11700 (2017) https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-10-11692 The algorithm used in the work may be found on github, see link. Codes may be used freely, but please cite the above article

Global assessment of experimental climate warming on tundra vegetation: heterogeneity over space and time

Understanding the sensitivity of tundra vegetation to climate warming is critical to forecasting future biodiversity and vegetation feedbacks to climate. In situ warming experiments accelerate climate change on a small scale to forecast responses of local plant communities. Limitations of this approach include the apparent site-specificity of results and uncertainty about the power of short-term studies to anticipate longer term change. We address these issues with a synthesis of 61 experimental warming studies, of up to 20 years duration, in tundra sites worldwide. The response of plant groups to warming often differed with ambient summer temperature, soil moisture and experimental duration. Shrubs increased with warming only where ambient temperature was high, whereas graminoids increased primarily in the coldest study sites. Linear increases in effect size over time were frequently observed. There was little indication of saturating or accelerating effects, as would be predicted if negative or positive vegetation feedbacks were common. These results indicate that tundra vegetation exhibits strong regional variation in response to warming, and that in vulnerable regions, cumulative effects of long-term warming on tundra vegetation – and associated ecosystem consequences – have the potential to be much greater than we have observed to date