Tunneling two level systems in superconducting circuits a new take on an old problem

by Moshe Schechter

at Condensed Matter Theory Seminar

Wed, 05 Dec 2018, 13:30
Physics building (#54) room 207


The generic existence of tunneling two level systems TLSs in amorphous solids was postulated to explain the intriguing universality of the acoustic properties of strongly disordered systems at low temperatures Yet over more than four decades later the nature of the tunneling states as well as the explanation of universality are still under debate Much of the recent interest in TLSs is a result of TLSs being a dominant source of noise in various devices such as superconducting microwave resonators single electron transistors nanomechanical resonators and superconducting qubits Whereas their coupling to these systems is deleterious from the point of view of coherent operetaion it opens up novel possibilities to study individual and ensembles of TLSs against various models describing their characteristics In this talk I will discuss recent studies of individual TLS dynamics as function of varying bias energy as studied by their coupling to a phase qubit as well as nonlinear response of an ensemble of TLSs coupled to superconducting microresonators Theoretical analysis within the standard tunneling model and within a recently proposed two TLS model will be described The latter model suggests the generic existence of two types of TLSs differing by their extent of deviation from symmetry under local inversion and consequently by their coupling strength to the strain It provides an explanation for the universality of the acoustic properties in strongly disordered solids at low temperatures as well as an explanation to recent experimental data on TLS dynamics and nonlinear response some of which can not be satisfactorily explained by the standard tunneling model

Created on 30-11-2018 by Bar Lev, Yevgeny (ybarlev)
Updaded on 30-11-2018 by Bar Lev, Yevgeny (ybarlev)