A great day out in celebration of Maxwell’s equations

Pillars of light: this week’s meeting at the Royal Society focused on how Maxwell’s equations illuminate physics. (CC BY-SA 3.0 Tom Morris)

By Hamish Johnston

Earlier this week I caught the 6.30 a.m. train from Bristol to London to attend the second day of “Unifying physics and technology in light of Maxwell’s equations” at the Royal Society. It was a particularly damp and gloomy morning as I emerged from Piccadilly Circus station and tramped through St James, my sights set on the Duke of York pillar next to the Royal Society in Carlton House Terrace.

It seemed like the perfect morning to be thankful for the light described by James Clerk Maxwell’s equations, and to ponder how they have since illuminated many shadowy corners of physics.

The meeting was organized by three physicists at nearby King’s College London: biophysicist and nanotechnologist Anatoly Zayats; particle physicist John Ellis and condensed-matter physicist Roy Pike. Already, you can see the breadth of physics covered at the meeting.

Unfortunately I missed the first day of the conference, when much of the focus was on particle physics, but I did manage to chat with some of Monday’s speakers during lunch and coffee on Tuesday. These included Nobel laureate Frank Wilczek who was in the UK recently promoting his new book on beauty and appearing on two BBC radio programmes: Private Passions and Start the Week. He told me that he is now collaborating on a new encyclopaedia of physics, which sounds like a very ambitious project indeed.

One thing I love about visiting the Royal Society is admiring the portraits of famous fellows that adorn the walls. Wilczek seems to share my passion and has composed an amusing “illustrated novelette” based on the portraits of John and Louisa Tyndall. Did she or didn’t she? We will probably never know!

I also ran into Jim Virdee, who works on the CMS experiment at CERN’s Large Hadron Collider and spoke on Monday about physics beyond the Standard Model. He told me that CMS physicists are now busy doing a “blind” analysis of data collected during the 13 TeV run. This involves covering up regions in the data where physicists expect to see evidence of new particles while the data are being processed. This avoids an unconscious – or indeed a conscious – bias towards processing the data in such a way that this evidence grows. Virdee says that the first results of this analysis should be available next summer.

Enough chit-chat over coffee, let’s get to the main event. The first Tuesday speaker was David Payne of the University of Southampton who tried to convince us that “optical fibres are the best electromagnetic waveguides ever”. But best is not good enough, and Payne spent most of his talk explaining how new hollow fibres will be even better than the solid ones used today.

Next up was Federico Capasso, who has had an incredibly productive career in optics, first at Bell Labs and lately at Harvard University. Capasso spoke about his work on making “flat lenses” – 2D objects with the same focusing power as the familiar 3D lenses used in cameras. An obvious application is mobile-phone cameras because the thinness of a phone is often limited by the thickness of its camera. Capasso is also working on a 2D lens that has no chromatic aberration for light at three different colours – red, green and blue. This, he says, could be used to create a wearable display that focuses images into your eye.

The talk with the biggest “wow factor” came from Thomas Ebbesen, who is a physical chemist at the University of Strasbourg. He spoke about “QED chemistry” that occurs when molecules are placed between two mirrors. Amazingly, the molecules couple with the dark (or vacuum) electromagnetic mode of the cavity to create quasiparticles with quantum states that can be very different than that of molecules on their own. “Vacuum is not nothing,” explained Ebbesen, who said that the effect could be used to boost the sensitivity of Raman spectroscopy. Expect to hear much more about QED chemistry in the future. Another fantastic light–matter interaction was highlighted by Harvard’s Mikhail Lukin, who spoke about using the Rydberg blockade in ultracold gases to make photons interact with each other in quantum-information devices. A Rydberg blockade allows Lukin to “stop” one photon and then collide it with a second photon – something that is nigh on impossible in conventional optical materials.

Getting photons to interact was also the theme of the talk by Ruth Oulton of the University of Bristol. She explained why embedding quantum dots in a photonic crystal could solve the tricky problem of exchanging quantum information between flying qubits and stationary qubits.

Also on the bill was John Pendry of Imperial College London, who is famous for his contributions to the development of invisibility cloaks. He spoke about how the theory he developed to describe such cloaks – transformation optics – can be used to work out the electromagnetic properties of tricky shapes such as “kissing cylinders”. Ian Walmsley of the University of Oxford rounded off the afternoon with a talk that focused on linear optical quantum computing, which, incredibly, does not involve interactions between information-bearing photons.

It was a fantastic day of physics at the Royal Society and I am told that the slides of all the presentations along with accompanying audio will soon be available here.