124 research outputs found
Mutual information as an order parameter for quantum synchronization
Spontaneous synchronization is a fundamental phenomenon, important in many
theoretical studies and applications. Recently this effect has been analyzed
and observed in a number of physical systems close to the quantum mechanical
regime. In this work we propose the mutual information as a useful order
parameter which can capture the emergence of synchronization in very different
contexts, ranging from semi-classical to intrinsically quantum mechanical
systems. Specifically we first study the synchronization of two coupled Van der
Pol oscillators in both classical and quantum regimes and later we consider the
synchronization of two qubits inside two coupled optical cavities. In all these
contexts, we find that mutual information can be used as an appropriate figure
of merit for determining the synchronization phases, independently of the
specific details of the system
Characterising two-sided quantum correlations beyond entanglement via metric-adjusted f-correlations
We introduce an infinite family of quantifiers of quantum correlations beyond
entanglement which vanish on both classical-quantum and quantum-classical
states and are in one-to-one correspondence with the metric-adjusted skew
informations. The `quantum correlations' are defined as the maximum
metric-adjusted correlations between pairs of local observables with the
same fixed equispaced spectrum. We show that these quantifiers are entanglement
monotones when restricted to pure states of qubit-qudit systems. We also
evaluate the quantum correlations in closed form for two-qubit systems and
discuss their behaviour under local commutativity preserving channels. We
finally provide a physical interpretation for the quantifier corresponding to
the average of the Wigner-Yanase-Dyson skew informations.Comment: 20 pages, 1 figure. Published versio
The inhibition of the highly expressed miR-221 and miR-222 impairs the growth of prostate carcinoma xenografts in mice
MiR-221 and miR-222 are two highly homologous microRNAs whose upregulation has been recently described in several types of human tumors, for some of which their oncogenic role was explained by the discovery of their target p27, a key cell cycle regulator. We previously showed this regulatory relationship in prostate carcinoma cell lines in vitro, underlying the role of miR-221/222 as inducers of proliferation and tumorigenicity
The sudden change phenomenon of quantum discord
Even if the parameters determining a system's state are varied smoothly, the
behavior of quantum correlations alike to quantum discord, and of its classical
counterparts, can be very peculiar, with the appearance of non-analyticities in
its rate of change. Here we review this sudden change phenomenon (SCP)
discussing some important points related to it: Its uncovering,
interpretations, and experimental verifications, its use in the context of the
emergence of the pointer basis in a quantum measurement process, its appearance
and universality under Markovian and non-Markovian dynamics, its theoretical
and experimental investigation in some other physical scenarios, and the
related phenomenon of double sudden change of trace distance discord. Several
open questions are identified, and we envisage that in answering them we will
gain significant further insight about the relation between the SCP and the
symmetry-geometric aspects of the quantum state space.Comment: Lectures on General Quantum Correlations and their Applications, F.
F. Fanchini, D. O. Soares Pinto, and G. Adesso (Eds.), Springer (2017), pp
309-33
Measures of quantum synchronization in continuous variable systems
We introduce and characterize two different measures which quantify the level of synchronization of coupled continuous variable quantum systems. The two measures allow us to extend to the quantum domain the notions of complete and phase synchronization. The Heisenberg principle sets a universal bound to complete synchronization. The measure of phase synchronization is, in principle, unbounded; however, in the absence of quantum resources (e.g., squeezing) the synchronization level is bounded below a certain threshold. We elucidate some interesting connections between entanglement and synchronization and, finally, discuss an application based on quantum optomechanical systems. © 2013 American Physical Society
Mutual information as an order parameter for quantum synchronization
10.1103/PhysRevA.91.012301Physical Review A - AtomicMolecularand Optical Physics91
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