Creation of the quantum cat state by using the collisional interaction of Bose-Einstein condensate and estimation of the quantum state

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The purpose of the research is to create the quantum cat state with Bose-Einstein condensate of neutral atomic gas. We constructed the ultra high vacuum system to operate the double magneto-optical trapping and also made the clover-leaf type of the magnetic trap. While the Bose-Einstein condensate of ^<87>Rb atoms was successfully created, it was hard to suppress the residual magnetic field less than 10μG because of the magnetization of the shield box caused by the magnetic trap. We thus started constructing a new setup which creates Bose-Einstein condensate by using only optical trapping technique. We succeeded in constructing a YVO_4 laser with its wavelength of 1.06μm and its power of 10W. Introducing the output power of the YVO_4 laser into the Bow-tie cavity which includes the vacuum glass cell, we succeeded in creating the optical trap whose potential depth is enough deep to catch the laser cooled Rb atoms. It is noted that the system is already surrounded by the magnetic shield and we can keep ultra low residual magnetic field under the operation of the double magneto-optical trapping. The residual magnetic field is less than 10μG and the magnetic gradient is suppressed to 2uG/cm. We are planning to implement our initial purpose by using these experimental setups soon