Features

They're short, lasting just 65 femtoseconds, but the light pulses produced by Oxford scientists could be very important for quantum computing.

Why? Well that's almost fifty times shorter than any single photon previously produced and, in a quantum information device based on light (where photonic logic gates replace electronic ones), having a stream of identical, high-quality single photons on tap is vital.

Peter Mosley of Oxford's Ultrafast Group, co-author of a Physical Review Letters paper on the research, explained: ’It is possible to make photons in pairs by sending laser light through special crystals. When a pair has been created, the detection of one of these photons heralds the presence of its twin. However these twin photons are entangled, meaning that the properties of one photon are inextricably linked to those of its partner and detecting one can ruin the quantum state of the other.'

‘Our technique minimises the effects of this entanglement, enabling us to prepare single photons that are extremely consistent and, to our knowledge, have the shortest duration of any photon ever generated. Not only is this a fascinating insight into fundamental physics but the precise timing and consistent attributes of these photons also makes them perfect for building photonic quantum logic gates and conducting experiments requiring large numbers of single photons.'

In the Oxford experiment the pairs of photons made had a central wavelength of about 830 nm, at the border between visible and near-infrared light. Each of these photons was about 65 femtoseconds (65 millionths of a billionth of a second) long. In units of space, they were about 20 microns long. The shortest previously produced single photon was about 1 picosecond long.

'Creating single photons even under controlled conditions is extremely challenging,' said Peter. 'Even the purest laser light beam consists of many photons all bunched together. Our approach enables us to generate individual photon replicas, identical packets of light of very short duration that are ideal for quantum computing.'

Peter Mosley is a member of the Ultrafast Group, part of Oxford University's Department of Physics

What do you get if you mix mathematics, music, dance and sculpture? Probably something a lot like The 19th Step, an experimental project involving Oxford mathematician Marcus du Sautoy.

Marcus mentioned this to me a while back: how he had come across artists from many different disciplines who were fascinated by the work of Argentinian fabulist Jorge Luis Borges and wanted to join forces for a collaborative performance. The first performance is tonight at Roehampton University.

The flyer explains it like this: 'On the 19th Step of a basement staircase in a building about to be demolished in downtown Buenos Aires, writer Jorge Luis Borges imagines an aleph, a point in space that contains all other points (past, present and future)...'. Marcus will be performing alongside dancers and musicians to 'create a complex patterning of spaces, layering understanding of time, numbers and relationships.'

I remember being captivated by Borges's Labyrinths, a book of short stories that still casts a spell over my imagination today and acts as a touchstone of fiction with my circle of friends. It's a great Rubik's cube of a book, full of strange angles, patterns and configurations of the past, present and future. Every mathematician should read it... So should everyone else.

Are there active volcanoes on Venus? The latest results from ESA's Venus Express spacecraft have been taken by some scientists as firm evidence that there are, although others remain sceptical.

Venus Express measured a highly variable quantity of the volcanic gas sulphur dioxide in the planet's atmosphere: and while many firmly believe that this is linked to recent volcanic activity others argue that, because unlike on Earth there's no rain to scrub the atmosphere clean of sulphur dioxide, Express is detecting events that could have happened millions of years ago.

'We're only halfway through the mission, so we're not ready to say definitively one way or another on the basis of this evidence before we analyse all the data,' said Fred Taylor, a Venus Express Interdisciplinary Scientist from Oxford. 'However, there's plenty of indirect evidence for volcanic activity on Venus so, in my opinion, it's about how much activity is going on and the role it plays in the planet's climate. I think it's probably just a matter of time before we 'see' a volcano erupting.'

Because of their longevity in the atmosphere volcanic gases would have a much greater impact on the climate of Venus than they do on Earth: understanding their role in climate processes could help to explain how Earth's twin got a 'serious case of climate change'. Volcanism may also be behind the planet's cloudy weather as these are made of sulphuric acid, not water vapour.

Fred commented: 'It's still early in the life of the mission but if we can quantify the role volcanic activity plays in the climate it will help us to understand the global warming process on Venus and other planets, and how Venus - once so much like Earth - evolved into the hothouse planet it is now, and how it might change in the future.' 

Professor Fred Taylor from Oxford's Department of Physics will be speaking at the European Geosciences Union's Annual Assembly in Vienna 13-18 April 2008 and at a press session for the event.

The weather of our planetary neighbours is looking remarkably similar to our own: the latest observations of Saturn, undertaken by a team involving Oxford's Leigh Fletcher, show that its southern polar vortex has plenty in common with the hurricanes to be found here on Earth. Both have cyclonic circulation, a warm central 'eye' region surrounded by a ring of high clouds - the eye wall - and convective clouds outside the eye. In turn these polar 'saturnicanes' [!] resemble the polar vortices of Venus - even if these lack cold collars and aren't linked to convective clouds. Maybe all this shouldn't be that surprising as, despite the different local conditions, all planetary weather must be shaped by the same physical laws. So if we ever do make contact with intelligent beings from another world we'll always have something to talk to them about: the weather.

Ant colonies, schools of fish and flocks of birds all have a different kind of intelligence from individuals: Oxford scientists are amongst those finding ways of creating artificial 'swarm intelligence' to help perform all kinds of tasks - including designing new drugs.

Currently drug designers use NMR spectroscopy to model the structure of proteins and work out what shape drug molecules need to be to bind to specific protein receptors - but this is very time-consuming and can only be done efficiently by an expert. Andrew Pickford of Oxford's Department of Biochemistry and colleagues aim to cut the time it takes to calculate protein structure from months to hours, and make it much easier to use, by applying swarm intelligence techniques.

The approach has been tested successfully using proteins where the 3D structure is already well known and the NMR spectroscopy invention is being commercialised by Oxford University Innovation, the University of Oxford's technology transfer company. More details from Adam Stoten at Isis.