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Breakthrough study on exploring open quantum systems forms new theory
A collaboration of research between Durham University’s Dr. Nikitas Gidopoulos, formerly of ISIS at the Rutherford Appleton Laboratory, and Dario Calvani, Alessandro Cuccoli and Paola Verrucchi (from Italy’s University of Florence, National Institute for Nuclear Physics-INFN, and National Research Council-CNR) has been published in a major US scientific journal.
The ‘Proceedings of the National Academy of Sciences’ reports how this breakthrough study has brought together two diametrically different approaches to exploring open quantum systems, and formed the underlying theory. This includes shedding light on the understanding of coherence between quantum systems or a quantum system and its environment.
Defined by Feynman as “a part of the Universe”, this ‘open system’ has until now been largely untapped, disguised by the rest of the system around it, the ‘environment’. However the researchers have found that the behaviour of the principle system (focus of attention) depends, is influenced and often driven by its surrounding environment and the links with it (correlations).
The purpose of the paper was to propose a way of describing this link more precisely. “Looking at popular science texts, one usually reads that quantum mechanics is the part of physics that describes the behaviour of very small things, like atoms and subatomic particles”, says Dr Gidopoulos, “but it’s not just very small things that have a deep quantum mechanical origin, but particles with much larger masses whose effects we experience daily and often take them granted as classical”.
Left: In this analogy the open system is the bee and the environment the flowers: details of the bees evidently emerge but we can no longer understand some aspects of their behaviour, such as the relation between their being still in a point and the fact that there is a flower underneath. Whereas the bottom image shows that a theoretical approach to open quantum systems is possible, that corresponds to a representation where every single detail of the bees image is kept, together with the relevant correlations between their behaviour and the structure of the flowering field they are flying upon.
The team have applied these conceptual tools to analyse a paradigmatic example in the study of open quantum systems, with a view to studying more realistic/complicated problems and most importantly to study the dynamics of open systems in relation to their environment.
This includes, for example, applying a magnetic field to a spin, an effect once taken as classical, whereas now the team have found how the correlations of the underlying quantum entanglement between system and environment manifest.
So what does this mean? Well, quantum correlations or entanglement may be used in order to control/drive a quantum system that is influenced by its environment (quantum information transfer/quantum transport.) Also, these conceptual tools have the potential to become widely used as a theoretical formalism/methodology to study open quantum systems.
To read the published article click here
Comet Pan-STARRS arrives
A bright comet, C/2011 L4 (Pan-STARRS), is now visible to the naked eye, low down to the West after sunset.
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Durham Physicists discover existence of a new form of superconductivity
Physicists from Durham, the ISIS facility and Oxford have revealed the possible existence of a new form of superconductivity occurring in a molecule-based material, in a paper published in the journal Physical Review Letters this week.
Superconductivity is a phase of matter in which a material expels magnetic fields from its interior and electrical current flows with no resistance. The physics of superconductors is described by the Higgs mechanism, recently demonstrated at the LHC, and is therefore of great fundamental importance as well as presenting the possibility of loss-free power transport and efficient energy storage.
Using sub-atomic particles called muons, which are uniquely sensitive probes of magnetism, the researchers have investigated the magnetic and superconducting properties of the material TMTSF2(ClO4), an organic system whose electrons are forced to interact with their neighbours along one-dimensional channels. The resulting physical properties of TMTSF2(ClO4) have intrigued physicists for the last twenty years. Dr Tom Lancaster of Durham University, who carried out the muon measurements explained that "there were conflicting reports of the strength of the quantum mechanical wave function of this superconducting material, which we have resolved through a series of painstaking investigations using our muon techniques."
The research shows that the wave function of TMTSF2(ClO4) appears to be different from that of all previously reported superconductors.
Dr Lancaster said "we classify objects in quantum mechanics by their symmetries: whether they look the same after being moved around in various ways. It appears from our research that, under certain conditions, the wavefunction in TMTSF2(ClO4) might be consistent with a symmetry, known as 'odd frequency', which has never been seen before in a bulk superconducting material".
It is hoped that this research will allow a step towards the discovery of the mechanism behind unconventional superconductivity which is still mysterious and presents a barrier to the use of superconductors in technological applications.
Click here to view the full paper
Photon Interactions: Durham Physicists discover a whole new system for manipulating light
A team within the Department of Physics has achieved some exciting results recently by demonstrating controlled strong interactions between individual photons.
Led by Prof Charles Adams, Daniel Maxwell and his team generated a small ultracold atomic gas cloud in which strong interactions between neighbouring photons can be switched on and off using microwaves. The team believes that the technique could be used to create optical quantum logic gates in which single photons could be processed one at a time.
Optical photons make very good "flying" quantum bits (qubits) because they can travel hundreds of kilometres through fibres without losing their quantum information. However, it is very difficult to get such photons to interact either with each other or with "stationary" qubits.
To make them interact, these photons (the "signal") can be stored in the cloud of atoms with the help of a bright blue "control" laser beam. Together, they excite some atoms into a high energy level known as a Rydberg state, named after one of the pioneers of atomic structure. A few photons are trapped in Rydberg atoms when the control light is turned off. It is these Rydberg states that interact so strongly, both with each other and with microwaves beamed into the cloud. The states then turn back into photons when the control beam is switched back on.
Importantly, the released photon has the same direction as the signal laser because of constructive interference. In this system, the Rydberg state acts like a cavity to store the light, with the control beam effectively "opening the cavity" to release a photon.
Interactions between Rydberg-stored photons have been demonstrated by other groups, as has microwave control of qubits. But the combination of the two is unique, and provides a whole new system for manipulating light. It reveals unexpectedly rich behaviour that raises many questions for future study. The next steps will be to measure the interactions in different ways, and harness it in the specific manner required for quantum logic gates.
See the full Physics Viewpoint article for more information:
http://physics.aps.org/articles/v6/25
Blast Off for Durham Physics Rocket Scientist!
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Opening of Refurbished Teaching Laboratories
On 12th December the 2012 Rochester Lecturer (Professor Alain Aspect, Institut d’Optique, France) officially opened the newly refurbished physics teaching laboratories.
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New BP Undergraduate scholarships worth £5000
These scholarships are for "talented science, technology, engineering and maths undergraduates studying at nine selected universities across the UK". Durham is one of the universities selected to take part.
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Astronomy and the Northern Lights
As part of the new St Cuthbert's Society Research Forums, Gary Fildes, a SCR and an honorary graduand from the University, will deliver a talk entitled "Astronomy and the Northern Lights" at 8pm on Tuesday 20th November in the Arnold Wolfendale Theatre (Calman Learning Centre). This is a public event so all are welcome.
For more details about Gary Fildes, please see http://www.dur.ac.uk/news/newsitem/?itemno=14884
Celebrate Science
Celebrate Science included a wide range of stimulating science themed events and activities focused around a giant science marquee situated on Palace Green, as well as at various University locations around the city. The aim was to stimulate an interest in science and to inspire young people to study science in the future while putting the University at the heart of a fun, high-profile community event.
Surviving Warsaw 1939-1945: Untold Stories of Occupation and the Ghetto
Dr. Marek Szablewski will give a talk at 14:15pm on Sunday 11 November atHolgate House, Grey College. Dr Marek Szablewski, a Durham university physics lecturer born and brought up in Sheffield and has recently returned from an eight-week Winston Churchill Travelling Fellowship (www.wcmt.org.uk) to Europe. The aim of his Fellowship was to research his hidden Polish family history and the journey that brought his parents to Yorkshire after World War Two.
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Durham and Oxford join forces in new approach to Synthesising Superconductors
A team of scientists from Oxford and Durham Universities, in collaboration with researcher at the ISIS facility, Oxfordshire
have demonstrated that a new approach to synthesising superconductors results in a dramatic improvement in their useful properties.
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Durham Astronomers' work features on Astronomy Picture of the Day
An image created by Dr Nigel Metcalfe and Dr Peter Draper has been chosen to feature on the well-known NASA APOD (Astronomy Picture of the
Day) website for October 12th
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Doctoral Supervision Award to member of Staff
Peter Hatton has been awarded one of the University Doctoral Supervision awards in 2012. In his career at both Edinburgh and Durham he has helped over twenty doctoral research students complete their PhD’s, twelve of who are still active researchers and academics, including eight Professors. In many cases he continues to work with his ex-students many years after they left Durham.
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Flyby of Close Approach Asteroid Captured
As part of the commissioning of Physics' "Far-East-14" undergraduate telescope for the Astronomy Lab, the new-discovered asteroid 2012 QG42 was observed on the evening of 2012 September 11.
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Dr Aidan Hindmarch to join prestigious EPSRC Research Forum.
A panel of experienced researchers and EPSRC staff have invited Dr. Aidan Hindmarsh to accept one of the very first positions on the prestigious Early Career Forum for Manufacturing Research.
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Two Physics postgraduate students awarded prestigious thesis prizes by publisher Springer
Two recent postgraduate students in the Department of Physics, Elise Jennings and Jonathan Pritchard, have had their PhD theses chosen for publication in the prestigious Springer Theses series and each has also received an associated cash prize of €500.
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