Regensburg 2022 – scientific programme
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QI: Fachverband Quanteninformation
QI 12: Quantum Computing and Algorithms
QI 12.11: Talk
Thursday, September 8, 2022, 17:45–18:00, H8
Avoiding barren plateaus via transferability of smooth solutions in Hamiltonian Variational Ansatz — •Antonio Anna Mele1,2, Glen Bigan Mbeng3, Giuseppe Ernesto Santoro2, Mario Collura2, and Pietro Torta2 — 1Dahlem Center for Complex Quantum Systems, Freie Universität Berlin, 14195 Berlin, Germany — 2SISSA, Via Bonomea 265, I-34136 Trieste, Italy — 3Universität Innsbruck, Technikerstraße 21 a, A-6020 Innsbruck, Austria
A large ongoing research effort focuses on Variational Quantum Algorithms (VQAs), representing leading candidates to achieve computational speed-ups on current quantum devices. The scalability of VQAs to a large number of qubits, beyond the simulation capabilities of classical computers, is still debated. Two major hurdles are the proliferation of low-quality variational local minima, and the exponential vanishing of gradients in the cost function landscape, a phenomenon referred to as barren plateaus. Here we show that, by employing iterative search schemes one can effectively prepare the ground state of paradigmatic quantum many-body models, circumventing also the barren plateau phenomenon. This is accomplished by leveraging the transferability to larger system sizes of iterative solutions, displaying an intrinsic smoothness of the variational parameters, a result that does not extend to other solutions found via random-start local optimization. Our scheme could be directly tested on near-term quantum devices, running a refinement optimization in a favorable local landscape with non-vanishing gradients.