Coherent enhancement in noisy quantum metrology

21 06/2013

Friday, 21 Jun. 2013, 15:00 - 16:00

Workgroup Walther Group

Presenter: Prof. Roberto M. Serra, UFABC, São Paulo, Barzil
Host: Assoc.Prof. Philip Walther
Where: Kurt Gödel Hörsaal, Ground floor Strudlhofgasse 4, 1090 Vienna

Quantum devices enable a considerable improvement to the uncertainty bound in a parameter estimation, since unique features of non-classical correlations can be employed to outperform the so-called standard limit. Almost all quantum technologies operate with some level of noise and how quantum-enhancement fares in the presence of noise is still unclear. We show that, when a system in mixed multipartite quantum state is used to estimate a parameter, the information must be decoded by coherent interactions between the parts of the probe. On the other hand, noiseless quantum metrology protocols are adaptively additive for any pure entangled states, that is, no coherent processing is necessary in this case. This leads to an operational interpretation for the ability of performing coherent interactions in noisy parameter estimation and highlights a cornerstone difference between mixed and pure probe states. Operating a molecular ensemble quantum simulator driven by nuclear magnetic resonance techniques (NMR), we also experimentally demonstrate that processing a noise quantum probe by coherent interactions lead to a quantum advantage when compared to a local adaptive stagy. In the end of the talk, we will briefly comment a thermodynamic cost of acquiring information and some related perspectives concerning the experimental investigation of fluctuation theorems at quantum regime.