Quantum Information Processing and Quantum Communications

Beyond the Heisenberg uncertainty

aula 202 - Mercoledì 5 maggio ore 11.00
  Y.H. SHIH and M. D’ANGELO, Quantum Optics Laboratory,
University of Maryland, Baltimore County,
Baltimore, MD 21250

>VITAE: Yanhua Shih received his B.S. degree from Northwestern University, China in 1981 and his Ph.D. in Physics from the University of Maryland in 1987. He joined the faculty of the Department of Physics and started the Quantum Optics Laboratory at the University of Maryland in 1989. He is currently
appointed as the full professor of physics and the director of the Quantum Optics Laboratory. Since 1989, His laboratory has been recognized as one of the leading groups in the field of quantum optics that attempts to probe the fundamental problems of
quantum theory. His pioneering research on multi-photon entanglement has attracted national and international attention. Y.H. Shih received the 2002 Willis E. Lamb Medal, for his pioneering contributions to quantum electronics and especially the study of spatial coherence effects of multiphoton entangled states. In recent 10 years, he has published more then 50 papers in leading refereed journals and given more then 80 invited papers in national and international professional conferences and workshops.

Yanhua Shih
  Quantum entanglement is one of the most surprising consequences of quantum mechanics. Based on EPR‚s criteria, the presence of the d-functions d(p1+p2) and d(x1-x2) in the idealized entangled two-particle system, seems to represent a violation of the uncertainty principle. It is indeed true, from a statistical point of view, that correlation measurements realized on two independent particles must obey the inequalities:
D(p1+p2) > Max(Dp1, Dp2) and D(x1-x2) > Max(Dx1, Dx2).
The apparent contradiction between these classical inequalities and the EPR inequalities:
D(p1+p2) < min(Dp1, Dp2) and D(x1-x2) < min(Dx1, Dx2) has deeply troubled EPR and many other physicists. Our recent experiments have demonstrated that entangled two-photon systems satisfy the EPR inequalities. These experimental demonstrations also highlighted a number of novel practical protocols for high-precision timing and positioning applications. The accuracy in these measurements could overcome, in principle, the limitations imposed by the uncertainty principle. However, we show that this is not a violation of the uncertainty principle.