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CATEGORIES:Lennard-Jones Centre
SUMMARY:Optimizing Quantum Hardware Resources with Classic
al Stochastic Methods - Maria-Andreea Filip\, Univ
ersity of Cambridge
DTSTART;TZID=Europe/London:20211101T160000
DTEND;TZID=Europe/London:20211101T163000
UID:TALK162310AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/162310
DESCRIPTION:Current quantum computers are limited to small num
bers of noisy qubits with low decoherence times. H
ybrid quantum-classical algorithms have been devis
ed to make the most of these noisy intermediate sc
ale quantum (NISQ) devices. One of the most popula
r is the Variational Quantum Eigensolver (VQE) [1]
which is based around the classical optimization
of a quantum cost function. This method has found
applications in finding the ground state for chemi
cal systems. In this context\, the unitary coupled
cluster (UCC) [2] ansatz has resurfaced as a conv
enient parametrisation\, due to its relatively wel
l-behaved energy landscape\, and particle-number a
nd spin preserving properties. However\, the circu
its required to encode UCC on a quantum computer a
re often too deep to be implemented on current mac
hines. One way to reduce the size of these circuit
s is to decrease the number of parameters in the a
nsatz. Quantum Monte Carlo (QMC) methods have been
shown to be efficient at sampling the most import
ant contributions to a wavefunction first and ther
efore show promise as screening approaches for mor
e complicated methods. Therefore\, we present a st
ochastic implementation of UCC in the coupled clus
ter Monte Carlo (CCMC) framework [3]. The results
from this approach are shown to be in good agreeme
nt with conventional UCC and then the method is us
ed to screen cluster amplitudes for use in UCC-bas
ed VQE calculation. We obtain highly accurate resu
lts for a series of small molecules and show that
significant reductions in quantum resources 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. Kucharsk
i and J. Noga\, Chem. Phys. Lett\, 1989\, 155\, 13
3\n\n3. M.-A. Filip and A. J. W. Thom\, J. Chem. P
hys.\, 2020\, 153\, 214106\n\n4. M.-A. Filip\, N.
Fitzpatrick\, D. Muñoz Ramo and A. J. W. Thom\, 20
21\, arXiv:2108.10912
LOCATION:Dept of Chemistry\, Wolfson Lecture Theatre and Zo
om
CONTACT:Dr Christoph Schran
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