Quantum dynamics: Light and matter

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Quantum dynamics: Light and matter How do light and matter interact? This is a proposal for research into some of the quantum mechanical subtleties of photons and electrons - the particles of light and electricity - that arise when there are many electrons around, because the matter is condensed, and many photons around as well, due to the light being very intense. Remarkable things can happen. Some of the photons can split into two photons, or two photons can react to form two new photons. These new photons can be "entangled," with neither photon really being independent of the other even if they propagate kilometres away from each other. Many such entangled pairs can make a "squeezed vacuum," and there are states of light even more subtle than that. Their "non-classicalness" makes them an important resource for quantum information processing. But to use them we need to be able to control them. They should be on a "chip," just as are the electrons we use for information processing. How do we do that for photons and have them preserve their non-classicalness in the presence of scattering and other real-world imperfections? And what is the range of things we can really do with them? The electrons can behave in strange quantum mechanical ways too, especially if light interacts with them. In quantum mechanics different possible outcomes can interfere with each other, just as water waves can, and we can use this to make light speed electrons up in one direction or another, just as we choose. Then, like a car with its engine turned off, they will start to slow down. But playing the role of road and air resistance will be scattering with other electrons, and with particles of sound. Can we learn about all these "quasi-particles" in a solid by such experiments? Can we make a useful device using light to control electricity? And if an electron has a definite velocity, quantum mechanics requires that its position is not definite. How then do we think about the way an electric field at a particular position "drives" the electron? Do elementary concepts like resistance and capacitance make sense? As material and laser science progresses, leading to smaller and smaller solid state structures and shorter and shorter optical pulses, these kinds of phenomena will be crucial as quantum photonics and electronics merge into a single field that may have a profound impact on both our science and technology. Behind all of them are fundamental issues in physics.