April 25, 1017<\/p>\n
55N-2F Departments of Physics and Applied Physics Meeting Room, Nishi-Waseda Campus, Waseda University<\/p>\n
Prof. Daniel BURGARTH\u00a0 (Aberystwyth University, UK)<\/p>\n
English<\/p>\n
We investigate the possibility to suppress unbounded interactions between a finite dimensional system and an infinite dimensional environment through a fast sequence of unitary kicks on the finite dimensional system. This method, called dynamical decoupling, is known to work for bounded interactions, but physical environments such as bosonic heat baths are usually modeled with unbounded interactions, whence here we initiate a systematic study of dynamical decoupling for unbounded operator. We develop a sufficient decoupling criterion for arbitrary Hamiltonians and a necessary decoupling criterion for semibounded Hamiltonians. We give examples for unbounded Hamiltonians where decoupling works and the limiting evolution as well as the convergence speed can be explicitly computed. We show that decoupling does not always work for unbounded interactions and provide both physically and mathematically motivated examples.<\/p>\n