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【Part1】 14:00-15:00
Dr. Nobuyuki Takei (Assistant Professor, Ohmori group, IMS)
Title: "Weak measurement and collapse of wave function: A study of non-unitary process with cavity QED of single Yb atoms"
Abstract:
Quantum measurement, i.e., non-unitary process, has been believed to be irreversible. However, Royer found a method of restoring the wave function even after the measurement process [1,2]. Such a measurement is said to be reversible, and it can be implemented for single 1/2 spins by using Faraday rotation [3]. Since the information on the spin direction can be extracted through the Faraday rotation of optical probe pulses, the spin state changes or collapses in a non-unitary manner. However, if the rotation angle is small, or the measurement is weak, successive measurements can probabilistically cancel the measurement effect, and then the premeasurement state is restored completely. To implement such a reversible measurement, the detection of Faraday rotation due to a single 1/2 spin is inevitable. Accordingly, a cavity QED system is required. In this talk, we report on real-time detection of single Yb atoms with a cavity QED system, and also on the observation of Faraday rotation with the single atoms. This is the first step to realize the reversible measurement. [1] M. Ueda and M. Kitagawa, Phys. Rev. Lett. 68, 3424 (1992). [2] A. Royer, Phys. Rev. Lett. 73, 913 (1994). [3] H. Terashima and M. Ueda, Phys. Rev. A 74, 012102 (2006).
【Part2】 15:00-16:00
Dr. Giorgi Veshapidze (JSPS Fellow, Ohmori group, IMS)
Title: "Three-photon photo-associative ionization and it's coherent control experiments in Rb MOT at Kansas State University"
Abstract:
I will talk about the photo-association, followed by auto-ionization (PAI) in Rb MOT. The evidence will be provided to show, that the photo-association proceeds through the excitation along (5S+5S) -> (5S+5P) -> (5S+4D) -> (5P+4D) states in the case of all CW photo-association and along (5S+5S) -> (5S+5P) -> (5P+5P) -> (5P+4D) states in case when 5S -> 5P transition is induced by ultra-fast laser. The results of the PAI, induced by phase-shaped ultra-fast pulse will be also presented for various spectral phase function imposed on the fs pulse. An interesting phenomena of the delay in molecular ion production depending on the fs pulse shape will be also presented.
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