On March 6, 2006, Claude Cohen-Tannoudji (C. Cohen - Tannoudji), professor of the Institut de France and Ecole Normale Superieure, visited the National Time Service Center as "Chair Professor of Einstein" from the Chinese Academy of Sciences upon invitation, and accepted the appointment of being a visiting professor of the National Time Service Center gladly, stating that he will visit the Center aperiodically to exchange view with scientific researchers there timely on the latest developments in ultracold atomic physics technology and its application in such fields as quantum frequency standard, etc., follow closely the progress of relevant work, and give guidance with pleasure. On behalf of Tannoudji Laboratoire Kastler Brossel Laboratory in France, professor Cohen-Tannoudji also signed the agreement of accepting 1 to 2 senior visiting scholar(s) of the National Time Service Center. And Guo Ji, researcher and director of the National Time Service Center, expressed his gratitude to Cohen – Tannoudji for accepting the appointment of being a visiting professor at the National Time Service Center, and awarded the letter of appointment.