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DTSTAMP:20260404T145845Z
UID:1623848400@ist.ac.at
DTSTART:20210616T150000
DTEND:20210616T160000
DESCRIPTION:Speaker: Martin Larocca\nhosted by Maksym Serbyn\nAbstract: Var
 iational Quantum Algorithms (VQAs) have received considerable attention du
 e to their potential for achieving near-term quantum advantage. However\, 
 more work is needed to understand their scalability. One known scaling res
 ult for VQAs is barren plateaus\, where certain circumstances lead to expo
 nentially vanishing gradients. It is common folklore that problem-inspired
  ansatzes avoid barren plateaus\, but in fact\, very little is known about
  their gradient scaling. In this work we employ tools from quantum optimal
  control to develop a framework that can diagnose the presence or absence 
 of barren plateaus for problem-inspired ansatzes. Such ansatzes include th
 e Quantum Alternating Operator Ansatz (QAOA)\, the Hamiltonian Variational
  Ansatz (HVA)\, and others. With our framework\, we prove that avoiding ba
 rren plateaus for these ansatzes is not always guaranteed. Specifically\, 
 we show that the gradient scaling of the VQA depends on the controllabilit
 y of the system\, and hence can be diagnosed through the dynamical Lie alg
 ebra $\\mathfrak{g}$ obtained from the generators of the ansatz. We analyz
 e the existence of barren plateaus in QAOA and HVA ansatzes\, and we highl
 ight the role of the input state\, as different initial states can lead to
  the presence or absence of barren plateaus. Taken together\, our results 
 provide a framework for trainability-aware ansatz design strategies that d
 o not come at the cost of extra quantum resources. Moreover\, we prove no-
 go results for obtaining ground states with variational ansatzes for contr
 ollable systems such as spin glasses. We finally provide evidence that bar
 ren plateaus can be linked to the dimension of $\\mathfrak{g}$Join Zoom Me
 etinghttps://istaustria.zoom.us/j/99477145630?pwd=WjdhRTdvZmNTdkJoaGFhVWFj
 STNNUT09Meeting ID: 994 7714 5630Passcode: 555461
LOCATION:Online on Zoom\, ISTA
ORGANIZER:maksym.serbyn@ist.ac.at
SUMMARY:Martin Larocca: Diagnosing barren plateaus with tools from quantum 
 optimal control
URL:https://talks-calendar.ista.ac.at/events/3223
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