STFC Advanced Fellow at Surrey :-)

This week brought the news that our current Marie Curie Fellow Arnau Rios has won an STFC Advanced Fellowship. Not only does that mean that he has been judged to be one of the best and most promising young researchers in the fields funded by STFC (particle, astro & nuclear physics and related fields), but also, that he will be with us at the University of Surrey for the next five years. Well done, Arnau!

Talk on Friday

This Friday I'll be talking at the Farnham Geological Society on the use of isotopes in geological studies. See here for more details, and maybe see you there.

Phil Elliot orbituary?

Phil Elliot, who died in 2008, was an important figure in the field of nuclear structure, showing how mathematical group theory could be used to explain the complexities of nuclear structure from a simple point of view. The protons and neutrons in nuclei are somewhat colloquially said to move in "orbits," so perhaps this is why the journal Nuclear Physics A has just published an "orbituary".

First workshop of the year

I'm in Brighton attending the PRESPEC Workshop, aimed at discussing the sort of experiments my experimental colleagues will do at the GSI Facility in Germany. There have been all sorts of different topics discussed, from proton radioactivity (decay of a nucleus by emitting a proton), to isomeric states (long-lived excitations in a nucleus), to evolution of nuclear shapes as the number of neutrons or protons chances, to theoretical approaches to describe all these different things. Mine was a theoretical talk, covering the range of things that one can do with mean-field theories. I culminated with a movie that I think is pretty cool. It is of a simulation of a collision on two Uranium nuclei, which combine briefly, and the combined "compound" nucleus then splits into three. Such ternary fission is pretty exotic, and it would be good if the calculation turns out to be correct. I need to do a bit more work to come up with a predicted experimental signature. For now, I'd just like to be able to convert the movie into a much smaller file format, so that I could show it here. I'm sure the file size is not what it should be if it were efficiently encoded. Anyone know a way of reducing the size of an mpeg video file?

Quantum Mechanics and The Archers

As I was lazily enjoying the Bank Holiday on Monday, my mobile phone rang. I answered it to find a researcher for the BBC's PM programme asking me if I was an Archers fan and if I knew anything about Quantum Mechanics. The answer was yes on both counts. In truth, the older I get and the more I study physics, the more I realise that I don't understand things, but I think there's no doubt that I'm an Archers fan.

For the show's 60th Anniversary edition on Sunday, they had a double-length episode, with a cliff-hanger in which we heard a long running cast member's scream as he fell from the roof of his stately home. What we didn't know for sure is whether or not he died. I didn't think about it at the time as I listened, but others apparently made the link between this situation and the Schroedinger's Cat thought experiment. The BBC picked this up and wanted to have me on PM to discuss it. So... I said yes, and walked the 30 seconds to the BBC studios that I conveniently live next to(!) and before I knew it, I was pre-recording an interview with Eddie Mair about the link between not knowing whether Nigel, the Archers character, was alive or dead, and not knowing whether a cat, locked in a box with a phial of poison which opens according to a random event, is alive or dead.

I thought I'd sound a bit nervous at the start of the interview, before I relaxed a bit, but listening to it when it went out (which I never much like doing!) it was actually okay. I think I gave a reasonable account of Schroedinger's Cat for a Radio 4 audience, and I got to talk to the great Eddie Mair.

Thanks to Jim Al-Khalili for forwarding my number to the BBC. They asked him (and according to Twitter, lots of others) before finally finding someone qualified to talk both about the Archers and Quantum Mechanics. That's one interesting Venn diagram.

If you want to listen, and you read this before the 10th of January, you can listen again on the BBC website. I'm about 40 minutes in.

Radiation and Reason

Next Wednesday, Prof Wade Allison will be at the University of Surrey giving an evening Institute of Physics lecture based on his book "Radiation and Reason".

The talk is at 7pm in lecture theatre M, and is free to attend. Please turn up for a 7pm start, if you wish to come. I will summarise what he says here afterwards.

Here is a facebook event page for it, if you wish to register interest, but there's no obligation to.

Nuclei in Semiconductors

Semiconductors are substances who electronic structure is such that they are neither good electrical conductors nor insulators, but whose conduction properties may be altered by various means, chemical and physical to produce materials which can do all sorts of amazing things. Things like transistors, and all the technology that comes from them, things like solar cells, things like cheap LED lighting, like lasers for BlueRay players - like a lot of the neat things that get developed by my colleagues in the Advanced Technology Institute here at the University of Surrey.

Usually, people interested in semiconductor materials are not terribly concerned with the nuclei that hold the electrons in place, except that the nuclei have to be the right element, say Silicon, in order to have the right number of electrons and so the right electron structure. It's not always the case, though. One cutting edge of semiconductor research involves using quantum "spins" to make quantum computers. Spin is a kind of quantum angular momentum - to do with things rotating - though in the quantum world things don't have to rotate to have angular momentum. In spin-based semiconductor research (or "spintronics"), one tries to manipulate the orientation of a spinning electron to store information, rather than by presence or absence of a charge. This is one of the promising ways of creating a quantum computer.

Once one starts to deal with electron spins, however, the nuclei can start becoming interested. Silicon is element number 14, with 14 protons in each nucleus, and 14 electrons around a neutral silicon atom. Silicon comes in three naturally occurring isotopes, though: Si-28 with 24 protons and 24 neutrons but also Si-29 and Si-30 with one and two extra neutrons respectively. Si-28 and Si-30 have no nuclear spin, so they don't interfere with spin-based quantum computers, but Si-29 (like all odd-numbered isotopes) has a non-zero nuclear spin, and their presence in naturally occurring silicon causes the quantum computer states to decay, or "decohere". The solution? Make isotopically-enriched silicon, without the natural Si-29. It turns out not to be that easy to either make a sample sufficiently isotopically pure, or even get rid of other contaminants, as a paper published last week, cited below, shows. Surprising sometimes where nuclear physics issues pop up.


Witzel, W., Carroll, M., Morello, A., Cywiński, L., & Das Sarma, S. (2010). Electron Spin Decoherence in Isotope-Enriched Silicon Physical Review Letters, 105 (18) DOI: 10.1103/PhysRevLett.105.187602