Theoretical Physics Division seminar

Two atomic clocks designed, constructed, and tested by consortium of three Polish universities (Warsaw, Cracow, Torun) within the framework of the Polish Optical Atomic Clock project are based on strontium atoms. The atoms are slowed down, laser-cooled and trapped within a one-dimensional optical network. Laser is tuned to frequency of the ¹S₀-³P₀ transition. Relative stability of both clocks is beter than 10^-16 during 1000 s. Absolute frequency of the transition has been measured to accuracy of about 1 Hz.

Bell states are known to be maximally entangled among all two-qubit states, as the partial trace is maximally mixed. For four-qubit system there is no state, such that any of its two-party reduction, with respect to any possible splitting, is maximally mixed. We show that such states exist for four qutrits and discuss existence of such absolutely maximally entangled states in multipartite systems. Such states correspond to ’perfect tensors’ or multi-unitary matrices, i. e. unitary matrices, which remain unitary after certain reordering of their elements.

The Nobel Prize in Physics 2015 was awarded jointly to Takaaki Kajita and Arthur B. McDonald "for the discovery of neutrino oscillations, which shows that neutrinos have mass". In my seminar I will present the history of neutrino oscillation measurements and two experiments (led by the two laureates) that made the actual discovery: Super-Kamiokande in Japan and SNO in Canada. Current status of neutrino oscillation physics and Polish involvement in this field will also be presented.