[Phys-seminars] 2011-12-13 Lasers Seminar - TODAY!!!

barmash at bgu.ac.il barmash at bgu.ac.il
Tue Dec 13 08:39:26 IST 2011

Lasers Seminar - TODAY!!!

  DATE: 13-12-2011

  TIME: 3:30pm (Tue)

  PLACE: Physics building (#54) room 207

Look Before You Leap:
Open Quantum System Dynamics with Trapped-Ions and Free Photons

Roee Ozeri, The Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot, Israel

A physical state in quantum mechanics is represented by a vector in a complex vector space. The superposition principle allows for two such state vectors to be linearly added. Superposition states are unique to the quantum world and were never observed with states that macroscopically differ: a banana was never observed in a superposition of pointing in two directions. The reason most quantum mechanics text books give to explain this difference is that when measured, a superposition collapses onto one of the measurement eigenvectors, and that it is really hard to prevent a macroscopic object from being effectively measured. By looking at the banana, we collect photons that scatter from it and give away its orientation. In this talk I will describe experiments in which photons that are scattered from a single trapped-ion spin get correlated with the spin direction, thus reducing superposition states into classical states. I will show how the process of decoherence progresses a
 s the probability for photon scattering increases. I will show that by post-selecting events where a single photon was scattered a measurement basis for the spin is self-selected. By performing polarization measurements on the scattered photons we can project the ion-spin on this measurement basis. I will show the role ion-photon entanglement plays in determining the measurement basis. Finally I will show how we can use ion photon entanglement in order to reverse photon-scattering decoherence.

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