Combining intervals of ekpyrotic (ultra-slow) contraction with a (non-singular) classical bounce naturally leads to a novel cyclic theory of the universe in which the Hubble parameter, energy density and temperature oscillate periodically, but the scale factor grows by an exponential factor from one cycle to the next. The resulting cosmology not only resolves the homogeneity, isotropy, flatness and monopole problems and generates a nearly scale invariant spectrum of density perturbations, but it also addresses a number of age-old cosmological issues that big bang inflationary cosmology does not. There may also be wider-ranging implications for fundamental physics, black holes and quantum measurement.
— Read more on ScientificAmerican.com
Author(s): Florian Fröwis, Matteo Fadel, Philipp Treutlein, Nicolas Gisin, and Nicolas Brunner
The quantum Fisher information (QFI) of certain multipartite entangled quantum states is larger than what is reachable by separable states, providing a metrological advantage. Are these nonclassical correlations strong enough to potentially violate a Bell inequality? Here, we present evidence from t…
[Phys. Rev. A 99, 040101(R)] Published Wed Apr 17, 2019
Lüders conditionalization: Conditional probability, transition probability, and updating in quantum probability theory
Author(s): Krzysztof Ptaszyński and Massimiliano Esposito
We report two results complementing the second law of thermodynamics for Markovian open quantum systems coupled to multiple reservoirs with different temperatures and chemical potentials. First, we derive a nonequilibrium free energy inequality providing an upper bound for a maximum power output, wh…
[Phys. Rev. Lett. 122, 150603] Published Tue Apr 16, 2019
Emergence of the geometric phase from quantum measurement back-action
Emergence of the geometric phase from quantum measurement back-action, Published online: 15 April 2019; doi:10.1038/s41567-019-0482-z
Following a closed evolution in the Hilbert space, the state vector of a quantum system accumulates a geometric phase factor. A series of weak measurements reveal the origin of this in the back-action of any quantum measurement.