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Seeing many-body physics with quantum optics


Quantum mechanics inevitably implies that only a wave-function measurement can provide the ultimate control over matter. At the same time, the ascent of nanotechnology will eventually depend on whether or not one can control the wave function of interacting many-body systems. Yet, it seem nearly impossible to realize such a "quantum-state tomography" for interacting many-body systems.

I will overview the latest development in this field and explain how many-body theory and quantum optics [1] can be systematically combined to produce a new level of laser spectroscopy. In particular, I will show why the light-matter interaction has an inherent capability to directly excite targeted many-body states through light source's quantum-optical fluctuations.[2] This leads to a precise excitation and characterization of desired many-body states, as the first steps toward the many-body quantum-state tomography.

To characterize the quantum-optical response experimentally, one simply needs to collect a massive set of optical responses [3] to classical laser excitations. The quantum-optical responses can be projected from the classical data set by applying the so-called cluster-expansion transformation [4] (CET). As a proof of principle, I will analyze quantum-well measurements by CET projecting their quantum-optical absorption to Schr¨odinger's cat-state sources. The results expose a completely new level of many-body physics that remains otherwise hidden.[5]

[1] M. Kira and S.W. Koch, Semiconductor quantum optics, (Cambridge University Press, 2011).
[2] M. Kira and S.W. Koch, Phys. Rev. A 73, 013813 (2006); S.W. Koch, M. Kira, G. Khitrova, and H.M. Gibbs, Nature Mat. 5, 523 (2006); M. Kira and S.W. Koch, Prog. Quantum Electr. 30, 155 (2006).
[3] R.P. Smith, J.K. Wahlstrand, A.C. Funk, R.P. Mirin, S.T. Cundiff, J.T. Steiner, M. Schafer, M. Kira, and S.W. Koch, Extraction of many-body configurations from nonlinear absorption in semiconductor quantum wells, Phys. Rev. Lett. 104, 247401 (2010).
[4] M. Kira and S.W. Koch, Cluster-expansion representation in quantum optics, Phys. Rev. A 78, 022102 (2008).
[5] M. Kira, S.W. Koch, R.P. Smith, A.E. Hunter, and S.T. Cundiff, Quantum spectroscopy with Schr¨odinger-cat states, Nature Physics 7, 799-804 (2011).