****Technical Abstract**** Coincidence counting techniques will be employed to probe the temporal correlations and full counting statistics of microwave photons emitted by phase coherent conductors and parametrically modulated, nonlinear superconducting quantum cavities. The microwave photon counter element is a large-area Josephson junction. When the junction is appropriately biased, the absorption of a single microwave photon induces a transition to the voltage state, resulting in a large and easily measured classical signal. In the context of mesoscopic noise, microwave coincidence counting will provide access to the full statistics of the microwave radiation emitted by phase coherent conductors. The microwave photon statistics are directly related to the electron counting statistics, a subject of intense theoretical and experimental interest for a more than a decade. Moreover, multi-photon correlators of the noise will provide a window on electron-electron correlations and characteristic energy scales in mesoscopic samples such as quantum point contacts, tunnel junctions, and diffusive metallic nanowires. In the context of circuit quantum electrodynamics (cQED), microwave photon counting will provide access to temporal correlations of microwave photons emitted by nonlinear superconducting quantum cavities as a rigorous probe of QED in the strong coupling regime. Correlations of emitted photons in parametrically modulated cavities will serve as a probe of the quantum radiation due to the dynamical Casimir effect. This experiment-theory program is rich in educational opportunities for participating students.

Nontechnical Abstract

To fully characterize an electronic device, one must measure not only the average current through the device, but also the fluctuations or "noise" of that current. In a large scale electrical resistor, many independent electrons contribute to the current and the fluctuations are distributed according to the familiar bell curve. For an ultrasmall or mesoscopic electronic device, however, charge transport is governed by the laws of quantum mechanics, and strong interactions between electrons or between electrons and their environment can imprint subtle signatures on the fluctuations. In this case, electronic noise can be used as a powerful probe of the underlying physical mechanisms that govern transport. This program is devoted to a study of noise and fluctuation statistics in these mesoscopic conductors, where transport involves the motion of single or few electrons and where quantum effects and strong interactions of the charge carriers play a critical role. The experiments will employ a newly developed superconducting detector that is sensitive to single microwave photons emitted by the mesoscopic conductors. This program will deepen our basic understanding of electronic transport in the quantum regime. This understanding will be essential to evaluate the performance of novel electronic devices as device scales become ever smaller, to the point where quantum phenomena can no longer be ignored. Detection technology developed during the course of this program could lead to advances in measurement for a variety of applications ranging from quantum information science to astrophysics. This program will involve the extensive participation of graduate researchers, and is rich in educational opportunities for both experimenters and theorists.

National Science Foundation (NSF)
Division of Materials Research (DMR)
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Guebre X. Tessema
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University of Wisconsin Madison
United States
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