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VERSION:2.0
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PRODID:UW-Madison-Physics-Events
BEGIN:VEVENT
SEQUENCE:2
UID:UW-Physics-Event-8073
DTSTART:20221221T163000Z
DTEND:20221221T183000Z
DTSTAMP:20260414T113312Z
LAST-MODIFIED:20221219T160357Z
LOCATION:Chamberlin 4274 or https://uwmadison.zoom.us/j/92025780578?pw
 d=ajhxalhFQlZBeCtGdzZXWnNLUXc4dz09  (passcode 630477)
SUMMARY:Valley splitting and alloy disorder in Si/SiGe quantum dots\, 
 Preliminary Exam\, Merritt Losert\, Physics Graduate Student
DESCRIPTION:Silicon/silicon-germanium heterostructures have many impor
 tant advantages for hosting spin qubits. However\, controlling the ene
 rgy splitting between the two low-energy conduction-band valley states
  remains a critical challenge for scaling up to large numbers of relia
 ble and reproducible qubits. Broad distributions of valley splittings 
 are commonplace\, even among quantum dots on the same device. Such beh
 avior has previously been attributed to imperfections such as steps at
  the quantum well interface\, which are known to strongly suppress the
  valley splitting. Many heterostructure designs have been proposed to 
 boost the valley splitting\, to overcome this problem. In this talk\, 
 we explore a simple\, universal theory of valley splitting based on th
 e reciprocal-space profile of the quantum-well confinement potential\,
  which can explain the effects of steps\, wide interfaces\, alloy diso
 rder\, and custom heterostructure designs. We use this understanding t
 o theoretically characterize the valley splitting in a variety of hete
 rostructures\, finding that alloy disorder causes substantial variatio
 ns of the valley splitting\, even in the absence of steps. Using this 
 understanding\, we lay out two approaches to engineer large valley spl
 ittings: one based on deterministically increasing the Fourier compone
 nt of the quantum well potential that couples the valleys\, and one th
 at takes advantage of disorder to statistically increase the valley sp
 litting.
URL:https://www.physics.wisc.edu/events/?id=8073
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