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VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
BEGIN:VEVENT
SEQUENCE:0
UID:UW-Physics-Event-3497
DTSTART:20141211T160000Z
DURATION:PT1H0M0S
DTSTAMP:20260419T161447Z
LAST-MODIFIED:20141208T143235Z
LOCATION:5310 Chamberlin Hall
SUMMARY:Probing the Materials Origins of Decoherence in Superconductin
 g Qubits\, R. G. Herb Condensed Matter Seminar\, Dr. Vincenzo Lordi\, 
 Lawrence Livermore Lab
DESCRIPTION:The practicality of superconducting qubits for scalable qu
 antum computing applications is limited by decoherence noise that redu
 ces the useful lifetime of the quantum states. While various theories 
 explain possible mechanisms for the decoherence\, the microscopic orig
 ins at the level of the materials comprising actual devices remain lar
 gely unknown. Such knowledge is essential to enabling rational improve
 ment of fabrication processes for higher performing qubits. First-prin
 ciples simulations at the atomic level provide a useful tool to probe 
 the materials origins of decoherence. Here\, we discuss recent work in
 vestigating magnetic fluctuators associated with materials defects tha
 t can contribute decoherence noise in these systems. In particular\, n
 ative defects and adsorbates on the surface of sapphire and dangling b
 ond defects on the surface of amorphous silica will be discussed. In a
 ddition\, interactions among spins on surfaces can be important\, and 
 we present detailed calculations on the energetics of such interaction
 s. We find that the spin-spin coupling strength can be strongly influe
 nced by lattice strain and the presence of defects. Finally\, an analy
 sis of the correlations between local structural and electronic proper
 ties of amorphous materials will be presented in this context.
URL:https://www.physics.wisc.edu/events/?id=3497
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