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Neoclassical light – An assessment of the voyage into Hilbert space

2009; IOP Publishing; Volume: 196; Linguagem: Inglês

10.1088/1742-6596/196/1/012015

1742-6596

H. J. Kimble,

Quantum optics and atomic interactions

I thank Rodger Walser and his colleagues for organizing this conference to celebrate George Sudarshan’s birthday and landmark achievements in science. It is an honor for me to be here and also a great pleasure to be back in Austin to join the chorus of the FOGS. I would like begin with a brief historical introduction and then turn to topics that we haven’t heard so much about thus far in the symposium, namely experiments in Quantum Optics. Let me remind you that blackbody radiation has had a profound impact on physics since the time of Planck. However, even in more modern times after the development of quantum mechanics and quantum electrodynamics, one really did not know how to describe the underlying field fluctuations as required for diverse interference phenomena. Emil Wolf laid critical foundations for this enterprise with his theory of classical coherence developed in collaboration with Max Born in their classic book Principles of Optics. A great challenge to the physics community was the experiment by R. H. Brown and R. Q. Twiss in 1956 [1], which led to a confusing and controversial time for photons and fields. In 1958 Leonard Mandel helped to resolve the controversy by explaining how light fluctuations are converted to photocurrents in the detection process, albeit in with a classical description of the field [2]. The confusion arose from the effort to understand, on the one hand, interference phenomena that are expressed in terms of the complex amplitude of the electromagnetic field, for which only a classical description was available. On the other hand, quantum electrodynamics had been developed based upon energy eigenstates (i.e., Fock states) with photons as quanta. It was really difficult to understand how the electric and magnetic fields behave in terms of these quantum states. For example, the expectation value of any electromagnetic field is zero in a Fock state. The confusion was compounded by the historic invention of the maser and laser and by the pressing need for quantum theories of the dynamical processes of these and other laboratory advances.