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First measurements of the differential positronium-formation cross-sections

Positrons are the antimatter version of electrons and so their fate in a matter world is ultimately to annihilate. However, prior to this, a positron may combine with an electron to form a matter-antimatter hybrid called positronium. This is akin to a hydrogen atom with the proton replaced by a positron. Fundamental to our understanding of the physical universe, positron and positronium are these days also acknowledged as being fantastically useful in practical applications such as probing material properties and medical diagnostics. However, there is still much that we do not know for sure about the details of the interactions of these particles with ordinary matter. For example if, in a collision with an atom or molecule, a positron captures an electron, in which directions is the positronium likely to travel and with what probability? More...

Published: Jun 17, 2015 12:35:19 PM

CO2 Satellite

New calculations to improve carbon dioxide monitoring from space

How light of different colours is absorbed by carbon dioxide (CO2) can now be accurately predicted using new calculations developed by a UCL-led team of scientists. This will help climate scientists studying Earth’s greenhouse gas emissions to better interpret data collected from satellites and ground stations measuring CO2. More...

Published: Jun 15, 2015 10:29:10 AM

Watt Steam Engine

On quantum scales, there are many second laws of thermodynamics

New research from UCL has uncovered additional second laws of thermodynamics which complement the ordinary second law of thermodynamics, one of the most fundamental laws of nature. These new second laws are generally not noticeable except on very small scales, at which point, they become increasingly important. More...

Published: Feb 10, 2015 11:55:53 AM

Theory of quantum collective effects in light-matter systems

There has been a tremendous progress in recent years in creating various strongly coupled light-matter systems where quantum collective effects can be explored.  These include, for example, semiconductor microcavities in strong coupling regime, superconducting qubits in microwave resonators, Rydberg states of atoms and ultracold atoms in optical cavities. Due to  their photonic part all those systems are subject to strong losses and so are intrinsically non-equilibrium. At the same time they are highly tunable and can be used to realise model Hamiltonians. To date several  
phase transitions such as BKT, BEC-BCS, superfluid-Mott and Dicke phase transition have been realised in one or more of these experimental settings.

The aim of this project is to study phase transitions and orders in non-equilibrium light-matter systems using analytical Keldysh field theory and/or numerical stochastic-type simulations. We aim to investigate how the non-equilibrium and dissipation affects the nature of these orders and  
to examine the potential of modern light-matter systems for simulating other less well controlled materials. The theoretical work under supervision of Dr Marzena Szymanska will be linked to experiments of Daniele Sanvitto's group (Lecce) on microcavities and David Schuster's group (Chicago) on circuit QED systems.

For further details please contact Dr Marzena Szymanska.