Unifying physics and technology in light of Maxwell's equations

09:05-09:30 Genesis of electroweak unification

Sir Tom Kibble CBE FRS, Imperial College London, UK

Abstract

The idea of unification has played a key role in the major advances in physics.  Maxwell’s unification of electricity, magnetism and light was one of the great steps forward. A more recent advance in the same direction was the development of the unified electroweak theory, incorporating the symmetry-breaking Higgs mechanism. This talk will review the early history of this development as seen from the standpoint of a member of Abdus Salam's group at Imperial College. It will describe the state of physics in the years after the Second World War, explain how the goal of a unified gauge theory of weak and electromagnetic interactions emerged, the obstacles encountered, in particular the Goldstone theorem, and how they were overcome, followed by a brief account of more recent history, culminating in the historic discovery of the Higgs boson in 2012.

• Listen to the audio recording - Professor John Ellis spoke on behalf of Sir Tom Kibble

09:45-10:15 Unification today

Professor Frank Wilczek, Massachusetts Institute of Technology, USA

Abstract

Maxwell's equations arose in the study of electrodynamics, but their influence in fundamental physics has been far wider.  Our present theories of the strong and weak subnuclear forces are based on profound, but conceptually simple, generalizations of Maxwell's equations.   The deep concept of local symmetry, which emerged from the study of Maxwell's equations, underlies all these theories, and also general relativity, our theory of nature's remaining force.  These commonalities give guidance for constructing a unified theory of all the forces.  In recent years the probable structure of that theory has clarified.  The unified theory leads to several qualitative and semi-quantitative insights that go beyond the theories of the separate forces, and to one major quantitative success.     The theory suggests many new phenomena, whose existence - or not - is the subject of ongoing experimental investigations.

In this talk I will attempt to convey a meaningful flavor of the underlying ideas using appropriate metaphors and imagery, and an appreciation of some major live issues at the research frontier

• Listen to the audio recording

11:00-11:30 Standard model: how far can it go, and how can we tell?

Professor Jonathan Butterworth, UCL, UK

Abstract

The Standard Model of particle physics encapsulates our current best understanding of physics at the smallest distances and highest energies. It incorporates Quantum Electrodynamics (the quantised version of Maxwell’s electromagnetism) and the weak and strong interactions, and has survived unmodified for decades, save for the inclusion of non-zero neutrino masses after the observation of neutrino oscillations in the late 1990s. Butterworth will review a selection of these successes, including the remarkably successful prediction of a new scalar boson, a qualitatively new kind of object observed in 2012 at the Large Hadron Collider. New calculational techniques and experimental advances challenge the Standard Model across an ever-wider range of phenomena, now extending significantly above the electroweak symmetry breaking scale. Butterworth will outline some of the consequences of these new challenges, and discuss some speculative ideas of new physics which there may still be to find within the Standard Model itself.

• Listen to the audio recording

11:45-12:15 Beyond the standard model of particle physics

Professor Tejinder Virdee FRS, Imperial College London, UK

Abstract

The Large Hadron Collider (LHC) at CERN and its experiments were conceived to tackle the profound open questions in particle physics, such as why the particles carrying the weak interactions are massive whereas the photon associated with Maxwell's theory is massless. The mechanism for generating particle masses has been elucidated with the discovery of the Higgs boson. Many open questions still await clues or answers, from the LHC and other experiments, including the composition of dark matter and of dark energy, why there is more matter than antimatter, do we live in more dimensions than the familiar four and what is the exact path to take to attain the unification of all the fundamental forces. This talk will discuss the status of, and prospects for, the search for new particles, symmetries and forces in order to address the open questions.

• Listen to the audio recording

12:30-13:00 Theoretical landscape beyond the Standard Model

Professor Veronica Sanz, University of Sussex, UK

Abstract

Collisions at high energies and intensity, light shining through walls, satellites deciphering the echoes of the Big-Bang - these are few examples of the ingenuity displayed in searching for physics beyond the Standard Model. Alas, proposals beyond the Standard Model abound, leading to a theoretical landscape which would seem far too extensive to be explored. However, this talk will explain how this search is about bringing to light new principles in Nature, principles which would explain the puzzles in the Standard Model and provide a deeper and more unified understanding of Particle Physics. These principles will then be used as a guide to describe the numerous proposals of new physics, as well as give examples of what kind of new phenomena they predict.

• Listen to the audio recording

14:15-14:45 Electromagnetism as an emergent phenomenon in condensed matter

Professor Roderich Moessner, Max Planck Institute for the Physics of Complex Systems, Germany

Abstract

Much of our understanding of physical order in the world around us is based on the notion of symmetry breaking. A case in point is the macroscopically detectable magnetistion direction of a ferromagnet, which disappears as symmetry is restored upon heating to a paramagnetic phase. More exotic is the situation of a phase which is not a paramagnet but still breaks no symmetry. Such a topological magnet can exhibit emergent gauge fields as natural degrees of freedom. This talk presents the case of spin ice, a magnetic material whose description takes on a form very close to that of Maxwell electromagnetism. Spin ice is able to sustain magnetically charged quasiparticles (`magnetic monopoles') linked by observable `Dirac strings'. In fact, its quasiparticles are doubly gauge charged, under both emergent as well as intrinsic Maxwell electromagnetism, exhibiting a fractional (irrational) magnetic charge for the latter.

15:30-16:00 Emergent electromagnetism and superconductivity

Professor Subir Sachdev, Harvard University, USA

Abstract

The theoretical implications of recent experiments on the copper-based high temperature superconductors will be presented. Models with long-range quantum entanglement are argued to describe key aspects of the observations. The representation of the quantum entanglement requires electric and magnetic fields, much  like those found in Maxwell’s theory. But here these fields `emerge’ from the quantum structure of the many-electron state, rather than being fundamental degrees of freedom of the vacuum.

• Listen to the audio recording

16:15-16:45 Experiments on emergent magnetic monopoles in spin ice

Professor Steven Bramwell, UCL, UK

Abstract

The idea of an electric field exciting charge pairs from a real or effective vacuum transcends science. Examples include thermionic emission (electron-image charge pair), Poole-Frenkel conduction (electron-hole pair), the second Wien effect of electrochemistry (anion-cation pair) and the Schwinger mechanism of excitation from the Dirac sea (electron-positron pair). Recent theoretical and experimental work  has confirmed the analogous process for the magnetic field-induced creation of emergent monopole-antimonopole pairs in spin ice. Here, the field-induced charge generation takes the form of a modified Wien effect, for which a remarkable (essentially exact) theory was derived by Onsager in 1934. This talk will describe the latest experiments to detect and characterise the Wien effect for emergent magnetic monopoles in spin ice . 

• Listen to the audio recording

09:00-09:30 Optical fibres: The best electromagnetic waveguides ever

Professor Sir David Payne CBE FREng FRS, University of Southampton, UK

Abstract

The publication by Kao and Hockham in 1965 of what has become accepted as the first serious analysis of the prospects for optical fibre communications had on its first page “Solving the Maxwell equations under the boundary conditions imposed by the physical structure….”, followed by the famous expressions for the optical modes in a cylindrical geometry and the observation that the lowest order HE11 mode in a fibre had no cut-off. Since that time, mode control in optical fibres has been key to optical fibre development, be it limiting the modal diffusion (coupling) in multimode fibres, to minimising bend or microbend losses, or to controlling the ‘modality’ and modal instability in high-power lasers operating at kilowatt levels.
The progress of optical fibres is charted over the decades through understanding the guidance conditions set out by Maxwell, or their ‘weakly-guiding’ simplifications.  Particular examples are at the two extremes of fibre performance, the 0.146 dB/km of today’s ULL (ultra-low loss) fibres and the remarkable kWatt power handling ability of large core fibres. The prospects for new air core fibres with very different guidance mechanisms than that analysed by Kao and Hockham will be examined and some predictions for the future will be made.

• Listen to the audio recording

09:45-10:15 Flat optics: physics and applications of structured light with metasurfaces

Professor Frederico Capasso, Harvard University, USA

Abstract

Patterning surfaces with subwavelength spaced metallo-dielectric features (metasurfaces) allows one to generate complex wavefronts by locally controlling the amplitude, phase and polarization of the scattered light. Recent results on achromatic lenses and collimators as well as chiral holograms will be presented. Metasurfaces have also become a powerful tool to shape surface waves. Professor Capasso will present experiments on imaging SPP that have revealed the formation of Cherenkov SPP wakes and their control with one dimensional metastructures and on polarization sensitive light couplers that demultiplex focused SPP beams depending on their wavelength and polarization.

• Listen to the audio recording

11:00-11:30 Hybrid light-matter states in dressed molecules

Professor Thomas Ebbesen, University of Strasbourg and CNRS, France

Abstract

When molecules or molecular materials are placed in the confined electro-magnetic fields which are resonant with a molecular transition, new hybrid light-matter states can be formed and the molecules are said to be 'dressed'. This can occur even in the dark due to strong coupling with the vacuum electromagnetic field.  The hybrid light-matter states are here collective states involving a large number of molecules and they may modify strongly the electronic and vibrational energy levels of the system. Such features have significant implications for molecular and material sciences that are just beginning to be explored. This potential will illustrated with examples from chemical reaction rates to bulk material properties.

• Listen to the audio recording

11:45-12:15 Maxwell, Einstein, and transformation optics

Sir John Pendry FRS, Imperial College London, UK

Abstract

Published 150 years ago Maxwell¹s equations were at least as startling as any of the modern advances in physics. They identified electricity and magnetism as the components of light, and laid the foundations for the special theory of relativity by requiring that they were reconciled with Newton¹s equations of motion. On their foundations mighty industries have been founded and to this day they still have new facets to be revealed.

The equations are known to be invariant under a coordinate transformation and this observation has been exploited in the new tool of transformation optics. Modern studies in electromagnetism go far beyond traditional optics often working in regimes where the length scales are much shorter than the wavelength where such intuitive but approximate rules such as Snell¹s law lose their validity. Transformation optics discards the concept of a ray and works instead with the electric and magnetic field lines which obey Maxwell¹s equations. Manipulating these fields gives back the intuitive feel of the ray picture but at the same time is exact.

Distortion of a field line can be represented as a transformation, which in turn tells what values of permittivity and permeability are needed to shape the fields in this way. Whilst adding nothing to the accuracy of the Maxwell¹s equations, this concept provides a picture on which we can unleash our imaginations. Applications to cloaking devices and to the sub wavelength design of plasmonic devices will be described.

• Listen to the audio recording

16:15-16:30 Closing remarks: from Maxwell’s electromagnetism to quantum technology

Sir Peter Knight FRS, Imperial College London, UK

Abstract

James Clerk Maxwell was responsible for a transformation in the way we regarded the electrical and magnetic forces, building on the experimental (and intuitive) notions of Michael Faraday to unite these in a single field-theoretic construct. In doing so he began the search for the unification of the fundamental forces that continues to dominate modern physics. This closing talk will stress how Maxwell’s work presaged special relativity (and indeed survived it) and how his field theoretic notions persisted in the new world of quantum theory, and indeed as previous talks in this meeting have demonstrated provide a framework to understand novel field theories, laser optics, transformation optics, quantum optics and the optics of novel materials.

13:30-14:30 Quantum enhanced technologies using light

Professor Ian Walmsley FRS, Imperial College London, UK

Abstract

Light enables exploration of quantum phenomena that illuminate the basic properties of nature, as well as enabling radical new technologies based on these phenomena. Indeed quantum optics has provided the impetus for many of the most far-reaching discoveries in quantum physics, yielding experimental evidence about quantum correlations that has changed the way in which we understand the natural world, such as, for instance, the inadequacy of local hidden variable models. Easily accessible quantum characteristics have also made quantum light a key enabler for emerging new technologies, primarily in new modes of information processing, including sensing, imaging, communications, simulation and computation. Indeed many of the cornerstone protocols of quantum information science were first realized optically, including teleportation and cryptography. Quantum optics is one of the most promising platforms for these new technologies, and it is driving forward the quantum information revolution. The critical features of quantum light that underpin the opportunities for discovery and application are exceptionally low noise and strong correlations. Rapid progress in both science and technology have been stimulated by adopting components developed for optical telecommunications and networking such as highly efficient detectors, integrated photonic circuits and wave-guide or nanostructure based non-linear optical devices. These provide the means to generate new quantum states of light and matter of unprecedented scale, which will contain many photons with quantum correlations across widely separated nodes of a network. Remarkably, networks with only several tens of photons are already beyond what can be efficiently analysed using current computers.

• Listen to the audio recording

14:15-14:45 New frontiers of quantum optical science

Professor Mikhail Lukin, Harvard University, USA

Abstract

Recent developments at a new scientific interface between quantum optics, nanoscience and quantum information science will be discussed. Specific examples include the use of quantum optical techniques for manipulation of individual atom-like impurities at a nanoscale and for realization of hybrid systems combining strongly coupled quantum emitters and nanophotonic devices. These techniques are used for realization of quantum nonlinear optics and quantum networks, and for new applications such as magnetic resonance imaging with single atom resolution. 

• Listen to the audio recording

15:30-16:00 Putting a spin on photonic crystal waveguides

Professor Ruth Oulton, University of Bristol, UK

Abstract

Quantum dots are semiconductor artificial atoms. They are nanoscale structures that trap single electrons and holes, and their quantized energy level structure results in atomic-like transitions and single photon emission. These quantum dots act as a solid-state interface that is useful for quantum information applications, and for the past decade, semiconductor physicists have been attempting to replicate atomic cavity quantum electrodynamics in a practical semiconductor form. One can embed quantum dot into micron-sized photonic structures to capture and control the light emission, in order to use the single photon emission in quantum communication and quantum circuits.

One of the most exciting applications of quantum dots is to use their electron spins as a quantum memory. This involves transferring spin information from an electron spin to the polarization of a photon. However, as I shall explain, the definition of 'polarization' for nanophotonic structures is far more complex than for a beam of light.  In fact, we find that point-like 'spin' emitters couple to a photonic structure in surprising ways: unlike any phenomenon observed in bulk material, simply changing the position of an emitter or the spin direction controls completely in which direction photons propagate. Suddenly, a rich variety of behaviour has arisen in the semiconductor/photonic domain which has no equivalent in atomic cavity QED, including a fundamental difference between how a classical dipole and a quantum dipole emitter interfere with incoming light.

• Listen to the audio recording