Universal decoherence induced by an environmental quantum phase transition

Decoherence induced by coupling a system with an environment may display universal features. Here we demostrate that when the coupling to the system drives a quantum phase transition in the environment, the temporal decay of quantum coherences in the system is Gaussian with a width independent of the system-environment coupling strength. The existence of this effect opens the way for a new type of quantum simulation algorithm, where a single qubit is used to detect a quantum phase transition. We discuss possible implementations of such algorithm and we relate our results to available data on universal decoherence in NMR echo experiments

Direct observation of quantum criticality in Ising spin chains

We use NMR quantum simulators to study antiferromagnetic Ising spin chains undergoing quantum phase transitions. Taking advantage of the sensitivity of the systems near criticality, we detect the critical points of the transitions using a direct measurement of the Loschmidt echo. We test our simulators for spin chains of even and odd numbers of spins, and compare the experimental results to theoretical predictions

Scientific big data visualization: A coupled tools approach

We designed and implemented a parallel visualisation system for the analysis of large scale time-dependent particle type data. The particular challenge we address is how to analyse a high performance computation style dataset when a visual representation of the full set is not possible or useful, and one is only interested in finding and inspecting smaller subsets that fulfil certain complex criteria. We used Paraview as the user interface, which is a familiar tool for many HPC users, runs in parallel, and can be conveniently extended. We distributed the data in a supercomputing environment using the Hadoop file system. On top of it, we run Hive or Impala, and implemented a connection between Paraview and them that allows us to launch programmable SQL queries in the database directly from within Paraview. The queries return a Paraview-native VTK object that fits directly into the Paraview pipeline. We find good scalability and response times. In the typical supercomputer environment (like the one we used for implementation) the queue and management system make it difficult to keep local data in between sessions, which imposes a bottleneck in the data loading stage. This makes our system most useful when permanently installed on a dedicated cluster