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SUMMARY:Optimizing Quantum Hardware Resources with Classical Stochastic Me
 thods - Maria-Andreea Filip\, University of Cambridge
DTSTART:20211101T160000Z
DTEND:20211101T163000Z
UID:TALK162310@talks.cam.ac.uk
CONTACT:Dr Christoph Schran
DESCRIPTION:Current quantum computers are limited to small numbers of nois
 y qubits with low decoherence times. Hybrid quantum-classical algorithms h
 ave been devised to make the most of these noisy intermediate scale quantu
 m (NISQ) devices. One of the most popular is the Variational Quantum Eigen
 solver (VQE) [1] which is based around the classical optimization of a qua
 ntum cost function. This method has found applications in finding the grou
 nd state for chemical systems. In this context\, the unitary coupled clust
 er (UCC) [2] ansatz has resurfaced as a convenient parametrisation\, due t
 o its relatively well-behaved energy landscape\, and particle-number and s
 pin preserving properties. However\, the circuits required to encode UCC o
 n a quantum computer are often too deep to be implemented on current machi
 nes. One way to reduce the size of these circuits is to decrease the numbe
 r of parameters in the ansatz. Quantum Monte Carlo (QMC) methods have been
  shown to be efficient at sampling the most important contributions to a w
 avefunction first and therefore show promise as screening approaches for m
 ore complicated methods. Therefore\, we present a stochastic implementatio
 n of UCC in the coupled cluster Monte Carlo (CCMC) framework [3]. The resu
 lts from this approach are shown to be in good agreement with conventional
  UCC and then the method is used to screen cluster amplitudes for use in U
 CC-based VQE calculation. We obtain highly accurate results for a series o
 f small molecules and show that significant reductions in quantum resource
 s can be achieved in a systematically improvable way [4].\n \n\nReferences
 \n\n1. A. Peruzzo\, J. McClean\, P. Shadbolt\, M.-H. Yung\, X.-Q. Zhou\, P
 . J. Love\, A. Aspuru-Guzik and J. L. O’Brien\, Nat. Commun.\, 2014\, 5\
 , 1\n\n2. R. J. Bartlett\, S. Kucharski and J. Noga\, Chem. Phys. Lett\, 1
 989\, 155\, 133\n\n3. M.-A. Filip and A. J. W. Thom\, J. Chem. Phys.\, 202
 0\, 153\, 214106\n\n4. M.-A. Filip\, N. Fitzpatrick\, D. Muñoz Ramo and A
 . J. W. Thom\, 2021\, arXiv:2108.10912
LOCATION:Dept of Chemistry\, Wolfson Lecture Theatre and Zoom
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