Searcharxiv⌕ Search

arXiv subjects

Ángel Rivas

Publications and source records attributed to Ángel Rivas.

40 records · Page 3Linked to original sources
arXiv2009

Nonclassicality of states and measurements by breaking classical bounds on statistics

We derive exceedingly simple practical procedures revealing the quantum nature of states and measurements by the violation of classical upper bounds on the statistics of arbitrary measurements. Data analysis is minimum and definite conclusions are obtained without evaluation of moments, or any other more sophisticated procedures. These nonclassical tests are independent of other typical quantum signatures such as sub-Poissonian statistics, quadrature squeezing, or oscillatory statistics. This approach can be equally well applied to very diverse situations such as single- and two-mode fields, observables with continuous and discrete spectra, finite- and infinite-dimensional systems, and ideal and noisy measurements.

quant-ph↗
arXiv2008

Intrinsic metrological resolution as a distance measure and nonclassical light

We elaborate on a Hilbert-Schmidt distance measure assessing the intrinsic metrological accuracy in the detection of signals imprinted on quantum probe states by signal-dependent transformations. For small signals this leads to a probe-transformation measure $Λ$ fully symmetric on the probe $ρ$ and the generator $G$ of the transformation $Λ(ρ, G) = Λ(G, ρ)$. Although $Λ$ can be regarded as a generalization of variance we show that no uncertainty relation holds for the product of measures corresponding to complementary generators. We show that all states with resolution larger than coherent states are nonclassical. We apply this formalism to feasible probes and transformations.

quant-ph↗
arXiv2008

Characterization of quantum angular-momentum fluctuations via principal components

We elaborate an approach to quantum fluctuations of angular momentum based on the diagonalization of the covariance matrix in two versions: real symmetric and complex Hermitian. At difference with previous approaches this is SU(2) invariant and avoids any difficulty caused by nontrivial commutators. Meaningful uncertainty relations are derived which are nontrivial even for vanishing mean angular momentum. We apply this approach to some relevant states.

quant-ph↗