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CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
BEGIN:VEVENT
SEQUENCE:1
UID:UW-Physics-Event-6413
DTSTART:20210427T140000Z
DURATION:PT1H0M0S
DTSTAMP:20260414T234050Z
LAST-MODIFIED:20210408T232230Z
LOCATION:https://uwmadison.zoom.us/j/96050486034?pwd=VlU2VHp3NmVSdkhMa
 lNuRGw5eFZ4QT09
SUMMARY:Heterostructure Modifications\, Fabrication Improvements\, and
  Measurement Automation of Si/SiGe Quantum Dots for Quantum Computatio
 n\, Thesis Defense\, Thomas McJunkin\, Physics PhD Graduate Student
DESCRIPTION:Quantum computing -- leveraging quantum phenomena to perfo
 rm complex and intractable computational problems -- has rapidly progr
 essed from a theoretical aspiration to a near reality. Currently\, the
 re are many competing approaches to the way the physical qubits (quant
 um bits) are built\, from trapped ions\, to superconducting circuits\,
  to semiconductor quantum dots\, and beyond. Here\, we focus on quantu
 m dots\, where electrons or holes are confined within a semiconductor 
 and the quantized nature of charge and spin are utilized for computati
 on. Within the field of quantum dots\, heterostructures made of silico
 n and silicon germanium are especially enticing due to their low densi
 ty of defects and nuclear spin. Although quantum dots are a promising 
 avenue for quantum computation because of their intrinsically small si
 ze and similarity to classical transistors\, nearly every aspect of th
 eir design\, realization\, and control has yet to be fully optimized.

 \nThis thesis explores modifications to the heterostructure\, fabricat
 ion\, and measurement of Si/SiGe quantum dots in the pursuit of improv
 ed quantum dot qubits. The valley splitting in silicon quantum dots\, 
 a near degeneracy of the lowest lying energy states\, is critical to t
 he formation and performance of silicon qubits. In this work\, we pres
 ent several modifications to the Si/SiGe heterostructure in an effort 
 to enhance this splitting. In particular\, we investigate the effects 
 of introducing germanium to the silicon quantum well by the inclusion 
 of a single spike in germanium concentration or an oscillatory concent
 ration throughout the well. We present experimental measurements of th
 e energy spectrum in both modifications and\, coupled with theoretical
  support\, claim enhancements to the valley splitting. Next\, we prese
 nt several fabrication techniques with the goal of improved quantum do
 t functionality and lowered charge noise\, a major barrier to higher q
 uality devices. We report a new strategy for etched palladium fabricat
 ion and discuss the current progress. Finally\, we present work toward
 s the automation of quantum dot tuning. As quantum dot devices increas
 e in the number of qubits\, so do the number of electrostatic gates wh
 ich control the device. We discuss the development of automated tuning
  procedures and present a routine for the formation of well-controlled
  quantum dots from the initial voltage settings.
\n
\nJoin Zoom Meetin
 g
\nhttps://uwmadison.zoom.us/j/96050486034?pwd=VlU2VHp3NmVSdkhMalNuRG
 w5eFZ4QT09
\n
\nMeeting ID: 960 5048 6034
\nPasscode: qubits
\n
URL:https://www.physics.wisc.edu/events/?id=6413
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