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Quantum Noise in Nuclear and Condensed Matter Physics
The noise is the signal
(INT Program May 6 - 31, 2013)

Reported by A. Andreev, L. Glazman, D.B. Kaplan
  Date posted July 30, 2013

Quantum fluctuations or "noise" are ubiquitous. Though treated as random in statistical approaches, fluctuations often arise from dynamical correlations between the underlying degrees of freedom of the physical system. In some situations noise complicates obtaining the information of interest from an experiment or a numerical simulation. In others, the physics one is interested in is contained in the noise itself (in the words of Rolf Landauer "the noise is the signal" [1]). In either case understanding and characterization the properties of the noise is crucial.

Although in systems with large numbers of particles fluctuations of macroscopic physical quantities usually obey a gaussian distribution, in many circumstances interesting physical phenomena correspond to atypical, rare fluctuations that do not follow a normal distribution.

Non-gaussian fluctuations occur as mesoscopic (sample to sample) static fluctuations caused by quenched randomness and temporal fluctuations of physical observables in a given system. Both static and dynamic fluctuations are accessible in experiments with mesoscopic solids, trapped cold atoms, and ensembles of photons in quantum optics settings. Remarkably, problems raised in the interpretation of such experiments are very similar to the problems in assessing the results of Monte Carlo simulations of quantum many-body systems, especially of simulations in nuclear and particle physics. There has been much recent and ongoing work in all of these fields. Despite the common issue - strong quantum fluctuations, researchers working in these areas customarily use different tools. The purpose of the program was to bring the practitioners of these areas together, facilitate exchange of expertise and scientific ideas between the rather disparate communities of condensed matter and nuclear physicists, and explore to what extent non-gaussian statistics observed in physical systems and their theoretical treatment share universal properties and common features.

The workshop was attended by over thirty participants. The program was subdivided into several overlapping periods according to the following themes: noise in quantum Monte Carlo simulations and the fermion sign problem, quantum fluctuations in cold atomic gases, and noise and quantum coherence effects in electron condensed matter systems. Most of the talks combined an introductory overview for non-experts with presentations of recent results and summary of outstanding problems. The format of the workshop provided ample time for discussions, both scheduled and spontaneous. This format worked very well. It helped to initiate many fruitful contacts between the participants, generate ideas for future research projects, and ferment new collaborations.

[1] R. Landauer, "Condensed-matter physics: The noise is the signal", Nature 392, 658( 1998).