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SUMMARY:Multireference State Preparation and Quantum Computed Moments in I
 nQuanto - Gabriel Greene-Diniz (Quantinuum)
DTSTART:20241106T120000Z
DTEND:20241106T140000Z
UID:TALK223642@talks.cam.ac.uk
CONTACT:Lila Cadi Tazi
DESCRIPTION:Quantum Subspace Methods (QSMs) have recently gained a lot of 
 interest\, in particular in the NISQ regime as a promising alternative to 
 variational quantum algorithms. In this talk\, we present recent work in w
 hich a QSM is used to quantum compute the Green's function\, with encourag
 ing results for the Hubbard model and Dynamical Mean Field Theory. To init
 ialise this approach\, as with most QSMs\, an initial state preparation is
  necessary\, and to this end we also present a technique to prepare a sele
 cted linear combination of Slater determinants on a quantum circuit. This 
 allows for an intuitive way to introduce quantum chemical multireference t
 echniques into quantum computational algorithms\, and when applied to a QS
 M involving Hamiltonian moments to 4th order\, results show a surprising i
 mpact on accuracy when evaluating the ground state energy of a strongly co
 rrelated molecule\, despite a low overhead of preparing initial states wit
 h accuracy beyond single-reference Hartree-Fock.
LOCATION:Chemistry of Health Meeting Room\, Department of Chemistry\, Camb
 ridge
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