In quantum mechanics\, the role of an observer is fundament ally different from that of a classical observer. \; The quantum mecha nical observer necessarily plays an active role in the dynamics of the sys tem that it is observing. \; This apparent difficulty may be turned in to a tool to drive an initially trivial system into a complicated quantum many-body state simply by observing it. \; I will present two remarkab le examples of states induced by measurement. In the first\, we examine th e role of a moving density measuring device interacting with a system of f ermions\, and in particular\, show that it would leave behind a wake of pu rely quantum origin. In the second example\, inspired by the recent invent ion of topological Floquet insulators\, we will see how a suitably chosen set of density measurements\, repeated periodically\, will induce robust c hiral edge motion on a lattice of free fermions. Our examples show how qua ntum mechanical observation can be added as a versatile tool to the arsena l of quantum engineering in condensed matter systems.

\n DTSTART:20210910T193000Z LOCATION:Physics Building\, Room 204 SUMMARY:Stirring by staring: Induced non-equilibrium states by measurements in quantum systems END:VEVENT END:VCALENDAR