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We relate the problem of irreversibility of entanglement with the recently defined measures of quantum correlation – quantum discord and one-way quantum deficit. We show that the entangle- ment of formation is always strictly larger than the coherent information and the entanglement cost is also larger in most cases. We prove irreversibility of entanglement under LOCC for a family of entangled states. This family is a generalization of the maximally correlated states for which we also give an analytic expression for the distillable entanglement, the relative entropy of entanglement, the distillable secret key and the quantum discord. Phys. Rev. Lett. 107, 020502 (2011) , also in http://xxx.lanl.gov/abs/1007.0228

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“Quantum measurement and control in optomechanical systems“

Prof. Gerard J. Milburn

The Univerity of Queensland, Brisbane, Australia

Director of the “Centre of Excellence in Engineered Quantum Systems”

The emerging field of quantum optomechanics combines quantum optics and new fabrication techniques to control the quantum state of macroscopic mechanical resonators. This now provides a new approach for controlling the mutual interaction between light and mesoscopic structures, which is one of the eminent goals in quantum information science and of importance for fundamental experiments at the quantum-classical boundary. I will give an overview of this new field and discuss some specific models. These include a scheme to conditionally prepare a macroscopic mechanical resonator in an energy eigenstate by measurement, single photon optomechanics, and quantum entanglement in optomechanical networks.

Date and time: 09 to 11/05/2011 at 14:00 and colloquium in 12/05/2011 at 16:00.

Place: Seminar room DFMC/IFGW/UNICAMP and colloquium hall IFGW

More information please go to the course page

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a) Schematic setup, with the central transmission line (resonator) capacitively coupled to the source and drain, and capacitively coupled to a SQUID-type qubit. (b) Variable energy levels of the qubit (0 < n < 1), with an external classical magnetic flux Φx(t). The resonator field is always blue detuned from that transition. J. Phys. B: At. Mol. Opt. Phys. 44 (2011) 135503. Also in http://xxx.lanl.gov/abs/1104.5189

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Occupational Husimi representation (left) and phase distribution (right) of the ground state for N = 30, Ω = −1, μ = 0 and self-collision parameter values: (a) χ=0, (b) χ=2 and (c) χ=3. In (b) we observe the squeezing in phase while the distribution in number broadens. The fragmentation of the phase in (c) characterizes a Quantum Phase Transition. See more in *Europhysics Letters 90, 10014 (2010). *

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