About QUINST

Quantum mechanics is at the heart of our technology and economy - the laser and the transistor are quantum devices - but its full potential is far from being realized. Recent technological advances in optics, nanoscience and engineering allow experimentalists to create artificial structures or put microscopic and mesoscopic systems under new manipulable conditions in which quantum phenomena play a fundamental role.

Quantum technologies exploit these effects with practical purposes. The objective of Quantum Science is to discover, study, and control quantum efects at a fundamental level. These are two sides of a virtuous circle: new technologies lead to the discovery and study of new phenomena that will lead to new technologies.

Our group's aim is  to control and understand quantum phenomena in a multidisciplinary intersection of  Quantum Information, Quantum optics and cold atoms, Quantum Control, Spintronics, Quantum metrology, Atom interferometry, Superconducting qubits and Circuit QED and Foundations of Quantum Mechanics.

 

 

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province:

Padam Miranowicz, Faculty of Physics, Adam Mickiewicz University, Poznan (Seminar)

When end where

12/2012

Description

2011/02/15, Padam Miranowicz, Faculty of Physics, Adam Mickiewicz University, Poznan
Place:  Sala de Seminarios del Departamento de Física Teórica e Historia de la Ciencia
Time: 11:45h.
Title: Experimentally-friendly criteria of nonclassicality and
entanglement of multimode fields.

Abstract
We consider a way to generate operational inequalities to test nonclassicality (or quantumness) of multimode bosonic fields (or multiparty bosonic systems) that unifies the derivation of many known inequalities and allows to propose new ones. The nonclassicality criteria are based on Vogel's criterion corresponding to analyzing the positivity of multimode $P$~functions or, equivalently, the positivity of matrices of expectation values of, e.g., creation and annihilation operators.
We analyze not only monomials, but also polynomial functions of such moments, which can sometimes enable simpler derivations of physically relevant inequalities. As an example, we derive various classical inequalities which can be violated only by nonclassical fields. In particular, we show how the criteria introduced here easily reduce to the well-known inequalities describing: (a) multimode quadrature squeezing and its generalizations including sum, difference and principal squeezing, (b) two-mode one-time photon-number correlations including sub-Poisson photon-number correlations and effects corresponding to violations of the Cauchy-Schwarz and Muirhead inequalities, (c) two-time single-mode photon-number correlations including photon antibunching and hyperbunching, and (d) two- and three-mode quantum entanglement.

Other simple inequalities for testing nonclassicality are also proposed. We have found some general relations between the
nonclassicality and entanglement criteria, in particular, those resulting from the Cauchy-Schwarz inequality. It is shown that some known entanglement inequalities can be derived as nonclassicality inequalities within our formalism, while some
other known entanglement inequalities can be seen as sums of more than one inequality derived from the nonclassicality criterion. This approach enables a deeper analysis of the entanglement for a given nonclassicality.