BEGIN:VCALENDAR
VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
BEGIN:VEVENT
SEQUENCE:0
UID:UW-Physics-Event-3277
DTSTART:20140403T150000Z
DURATION:PT1H0M0S
DTSTAMP:20260416T111905Z
LAST-MODIFIED:20140324T160314Z
LOCATION:Chamberlin 5310
SUMMARY:Measuring topological transitions in superconducting qubits\, 
 R. G. Herb Condensed Matter Seminar\, Michael Kolodrubetz\, Boston Uni
 versity
DESCRIPTION:The field of topological insulators sprung from the realiz
 ation that in the presence of spin-orbit coupling\, non-interacting el
 ectrons can have a band structure that non-trivially wraps the first B
 rillouin zone.  From the gauge-invariant Berry curvature that locally 
 defines the geometry of this wrapping\, one can define an integer topo
 logical invariant – the Chern number – from which all other invari
 ants derive.  We investigate the Berry curvature and Chern number of a
 n even simpler case: single and double spin-1/2 systems (qubits) in a 
 rotating magnetic field.  We show that these simple systems undergo to
 pological transitions of their Chern number\, which for the case of th
 e single qubit can be directly mapped to the topological transitions o
 f the Haldane model of graphene. Furthermore\, we experimentally demon
 strate such a topological transition in a single superconducting qubit
 \, measuring the Berry curvature as a leading order correction to line
 ar response.  We then generalize the methods to two-qubit systems\, wh
 ere we experimentally measure the topological phase diagram and demons
 trate interaction-driven topological transitions.
URL:https://www.physics.wisc.edu/events/?id=3277
END:VEVENT
END:VCALENDAR