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VERSION:2.0
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PRODID:UW-Madison-Physics-Events
BEGIN:VEVENT
SEQUENCE:0
UID:UW-Physics-Event-8932
DTSTART:20241025T180000Z
DTEND:20241025T200000Z
DTSTAMP:20260413T184743Z
LAST-MODIFIED:20240926T225816Z
LOCATION:5310 Chamberlin Hall\; https://uwmadison.zoom.us/j/9661985152
 3?pwd=rc7wIo6veBZBD3Ri4Fzkw8oOV5F3Rb.1#success 
SUMMARY:Alloy disorder\, valley splitting\, and shuttling for spin qub
 its in Si/SiGe heterostructures\, Thesis Defense\, Merritt Losert\, Ph
 ysics PhD Graduate Student
DESCRIPTION:Spin qubits in Si/SiGe heterostructures have several advan
 tages as scalable qubit platforms\, including their small size\, their
  long coherence times\, and their reliance upon conventional semicondu
 ctor fabrication methods. However\, microscopic disorder in the semico
 nductor structure impact these qubits in a variety of ways\, reducing 
 qubit yield. In particular\, the valley energy splitting (the energy g
 ap between the two low-lying conduction band valley states) is widely 
 variable\, and highly sensitive to microscopic disorder. In this disse
 rtation\, we study the effects of disorder on spin qubits formed from 
 quantum dots in Si/SiGe heterostructures\, focusing particularly on th
 e valley energy splitting. We demonstrate that alloy disorder (disorde
 r due to the random arrangement of Si and Ge atoms in the SiGe alloy) 
 has a profound impact on these qubits. We develop a theory to explain 
 the impact of alloy disorder on the valley splitting\, and we compare 
 the results of this theory to a variety of experiments\, finding good 
 quantitative agreement. We demonstrate that alloy disorder determines 
 the valley splitting in most realistic devices\, and we propose a high
 -Ge heterostructure that enhances alloy disorder in order to increase 
 average valley splittings.    We also examine the impact of alloy diso
 rder on long-distance qubit connectivity via conveyor-mode electron sh
 uttling. We demonstrate that alloy disorder leads to valley excitation
 s\, causing quantum information to leak out of the qubit subspace. We 
 develop a variety of schemes to mitigate these excitations\, by either
  avoiding valley excitations or mitigating their impact\, providing re
 cipes for high-fidelity spin shuttling in several device regimes.
URL:https://www.physics.wisc.edu/events/?id=8932
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