Effects of Interactions on the Critical Temperature of a Trapped Bose Gas

We perform high-precision measurements of the condensation temperature of a harmonically-trapped atomic Bose gas with widely-tuneable interactions. For weak interactions we observe a negative shift of the critical temperature in excellent agreement with mean-field theory. However for sufficiently strong interactions we clearly observe an additional positive shift, characteristic of beyond-mean-field critical correlations. We also discuss non-equilibrium effects on the apparent critical temperature for both very weak and very strong interactions.Comment: 4 pages, 4 figure

Efficient Production of Large 39K Bose-Einstein Condensates

We describe an experimental setup and the cooling procedure for producing 39K Bose-Einstein condensates of over 4x10^5 atoms. Condensation is achieved via a combination of sympathetic cooling with 87Rb in a quadrupole-Ioffe-configuration (QUIC) magnetic trap, and direct evaporation in a large volume crossed optical dipole trap, where we exploit the broad Feshbach resonance at 402 G to tune the 39K interactions from weak and attractive to strong and repulsive. In the same apparatus we create quasi-pure 87Rb condensates of over 8x10^5 atoms.Comment: 7 pages, 5 figures; figure font compatibility improve

Can a Bose gas be saturated?

Bose-Einstein condensation is unique among phase transitions between different states of matter in the sense that it occurs even in the absence of interactions between particles. In Einstein's textbook picture of an ideal gas, purely statistical arguments set an upper bound on the number of particles occupying the excited states of the system, and condensation is driven by this saturation of the quantum vapour. Dilute ultracold atomic gases are celebrated as a realisation of Bose-Einstein condensation in close to its purely statistical form. Here we scrutinise this point of view using an ultracold gas of potassium (39K) atoms, in which the strength of interactions can be tuned via a Feshbach scattering resonance. We first show that under typical experi-mental conditions a partially condensed atomic gas strongly deviates from the textbook concept of a saturated vapour. We then use measurements at a range of interaction strengths and temperatures to extrapolate to the non-interacting limit, and prove that in this limit the behaviour of a Bose gas is consistent with the saturation picture. Finally, we provide evidence for the universality of our observations through additional measurements with a different atomic species, 87Rb. Our results suggest a new way of characterising condensation phenomena in different physical systems.Comment: 6 pages, 5 figure

TRE-FX:Delivering a federated network of trusted research environments to enable safe data analytics

Trusted Research Environments (TREs) are secure locations in which data are placed for researchers to analyse. TREs host administrative data, hospital data or any other data that needs to remain securely isolated, but it is hard for a researcher to perform an analysis across multiple TREs, requesting and gathering the outputs from each one. This is a common problem in the UK's devolved healthcare system of geographical and governance boundaries. There are different ways of implementing TREs and the analysis tools that use them. A solution must be straightforward for existing, independent systems to adopt, must cope with the variety of system implementations, and must work within the "Five Safes" framework that enables data services to provide safe research access to data. TRE-FX assembled leading infrastructure researchers, analysis tool makers, TRE providers and public engagement specialists to streamline the exchange of data requests and results. The "Five Safes RO-Crate" standard packages up (Crates) the Objects needed for Research requests and results with the information needed for the tools and TRE providers to ensure that the crates are reviewed and processed according to Five Safes principles. TRE-FX showed how this works using software components and an end-to-end demonstrator implemented by a TRE in Wales. Two other TREs, in Scotland and England, are preparing to follow suit. Two analysis tool providers (Bitfount and DataSHIELD) modified their systems to use the RO-Crates. The next step is practical implementation as part of the HDR UK programme. Two large European projects will develop the approach further. TRE-FX shows that it is possible to streamline how analysis tools access multiple TREs while enabling the TREs to ensure that the access is safe. The approach scales as more TREs are added and can be adopted by established systems. Researchers will then be able to perform an analysis across multiple TREs much more easily, widening the scope of their research and making more effective use of the UK's data. If we had had this for COVID-19 data analysis, it would have super-charged researchers to be able to quickly answer pressing questions across the UK. This work was funded by UK Research & Innovation [Grant Number MC_PC_23007] as part of Phase 1 of the DARE UK (Data and Analytics Research Environments UK) programme, delivered in partnership with Health Data Research UK (HDR UK) and Administrative Data Research UK (ADR UK)

TRE-FX: Delivering a federated network of trusted research environments to enable safe data analytics

<p>Trusted Research Environments (TREs) are secure locations in which data are placed for researchers to analyse. TREs host administrative data, hospital data or any other data that needs to remain securely isolated, but it is hard for a researcher to perform an analysis across multiple TREs, requesting and gathering the outputs from each one. This is a common problem in the UK's devolved healthcare system of geographical and governance boundaries. </p><p>There are different ways of implementing TREs and the analysis tools that use them. A solution must be straightforward for existing, independent systems to adopt, must cope with the variety of system implementations, and must work within the "Five Safes" framework that enables data services to provide safe research access to data. </p><p>TRE-FX assembled leading infrastructure researchers, analysis tool makers, TRE providers and public engagement specialists to streamline the exchange of data requests and results. The "Five Safes RO-Crate" standard packages up (Crates) the Objects needed for Research requests and results with the information needed for the tools and TRE providers to ensure that the crates are reviewed and processed according to Five Safes principles. TRE-FX showed how this works using software components and an end-to-end demonstrator implemented by a TRE in Wales. Two other TREs, in Scotland and England, are preparing to follow suit. Two analysis tool providers (Bitfount and DataSHIELD) modified their systems to use the RO-Crates. The next step is practical implementation as part of the HDR UK programme. Two large European projects will develop the approach further. </p><p><strong>TRE-FX shows that it is possible to streamline how analysis tools access multiple TREs while enabling the TREs to ensure that the access is safe. </strong>The approach scales as more TREs are added and can be adopted by established systems. Researchers will then be able to perform an analysis across multiple TREs much more easily, widening the scope of their research and making more effective use of the UK's data. If we had had this for COVID-19 data analysis, it would have super-charged researchers to be able to quickly answer pressing questions across the UK. </p><p>This work was funded by UK Research & Innovation [Grant Number MC_PC_23007] as part of Phase 1 of the DARE UK (Data and Analytics Research Environments UK) programme, delivered in partnership with Health Data Research UK (HDR UK) and Administrative Data Research UK (ADR UK). </p&gt