S. Groeblacher, A. Trubarov, N. Prigge, M. Aspelmeyer, J. Eisert
At the heart of understanding the emergence of a classical world from quantum theory is the insight that all macroscopic quantum systems are to some extent coupled to an environment and hence are open systems. The associated loss of quantum coherence, i.e., decoherence, is also detrimental for quantum information processing applications. In contrast, properly engineered quantum noise can counteract decoherence and can even be used in robust quantum state generation. To exploit the detailed dynamics of a quantum system it is therefore crucial to obtain both good knowledge and control over its environment. Here we present a method to reconstruct the relevant properties of the environment, that is, its spectral density, of the center of mass motion of a micro-mechanical oscillator. We observe a clear signature of non-Markovian Brownian motion, which is in contrast to the current paradigm to treat the thermal environment of mechanical quantum resonators as fully Markovian. The presented method, inspired by methods of system identification, can easily be transferred to other harmonic systems that are embedded in a complex environment, for example electronic or nuclear spin states in a solid state matrix. Our results also open up a route for mechanical quantum state engineering via coupling to unorthodox reservoirs.
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http://arxiv.org/abs/1305.6942
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