Lecturer: Mr. Shlomi Matityahu Affiliation: Ben-Gurion University of the Negev Abstract: The low-temperature physics of amorphous and disordered solids has been a subject of great interest for more than four decades. Below about 1K the acoustic and thermodynamic properties of a large variety of glasses are not only qualitatively different compared to their crystalline counterparts, but also show a remarkable degree of universality. This universal behavior was explained by the existence of low-energy excitations with two- level structure, known as tunneling two-level systems (TLSs). Recent progress with microfabricated quantum devices has revealed that an ubiquitous source of noise originates in such TLSs. In this talk I will describe how individual TLSs in the Jospehson junction of a superconducting qubit can be probed and manipulated, and discuss a recent experiment in which Ramsey and spin-echo dephasing rates of individual TLSs were measured. I will show that most features of the Ramsey dephasing can be understood within the standard model of tunneling TLSs, whereas the spin-echo dephasing rate suggests the existence of some white noise environment. I will discuss a two- TLS model as a possible explanation for such an environment. ‏האירוע הזה כולל שיחת וידאו ב-Google Hangouts. הצטרף: https://hangouts.google.com/hangouts/_/mail.huji.ac.il/condensed?hceid=b...