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DTSTART:20240310T070000
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DTSTART:20231105T060000
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DTSTART;TZID=America/Toronto:20240410T120000
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URL:https://uwaterloo.ca/institute-for-quantum-computing/events/iqc-student
 -seminar-featuring-matthew-duschenes
LOCATION:QNC - Quantum Nano Centre 200 University Avenue West Room QNC 1201
  Waterloo ON N2L 3G1 Canada
SUMMARY:IQC Student Seminar Featuring Matthew Duschenes
CLASS:PUBLIC
DESCRIPTION:OVERPARAMETERIZATION AND EXPRESSIVITY OF REALISTIC QUANTUM SYST
 EMS\n\nQuantum-Nano Centre\, 200 University Ave West\, Room QNC 1201 Water
 loo\,\nON CA N2L 3G1\n\nQuantum computing devices require exceptional cont
 rol of their\nexperimental parameters to prepare quantum states and simula
 te other\nquantum systems\, in particular while subject to noise. Of inter
 est\nhere are notions of trainability\, how difficult is it to classically
 \noptimize parameterized\, realistic quantum systems to represent target\n
 states or operators of interest\, and expressivity\, how much of a\ndesire
 d set of these targets is our parameterized ansatze even capable\nof repre
 senting? We observe that overparameterization phenomena\, where\nsystems a
 re adequately parameterized\, are resilient in noisy settings\nat short ti
 mes and optimization can converge exponentially with\ncircuit depth. Howev
 er fidelities decay to zero past a critical depth\ndue to accumulation of 
 either quantum or classical noise. To help\nexplain these noise-induced ph
 enomena\, we introduce the notion of\nexpressivity of non-unitary\, trace 
 preserving operations\, and\nhighlight differences in average behaviours o
 f unitary versus\nnon-unitary ensembles. We rigorously prove that highly-e
 xpressive\nnoisy quantum circuits will suffer from barren plateaus\, thus\
 ngeneralizing reasons behind noise-induced phenomena. Our results\ndemonst
 rate that appropriately parameterized ansatze can mitigate\nentropic effec
 ts from their environment\, and care must be taken when\nselecting ansatze
  of channels.
DTSTAMP:20260419T090724Z
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