Unitary Selective Coupled-Cluster Method
- Argonne National Laboratory (ANL), Argonne, IL (United States); Oak Ridge Associated Universities (ORAU), Oak Ridge, TN (United States); General Atomics
- Argonne National Laboratory (ANL), Argonne, IL (United States)
- HRL Laboratories, LLC, Malibu, CA (United States)
Simulating molecules using the Variational Quantum Eigensolver method is one of the promising applications for NISQ-era quantum computers. Designing an efficient ansatz to represent the electronic wave function is crucial in such simulations. Standard unitary coupled-cluster with singles and doubles (UCCSD) ansatz tends to have a large number of insignificant terms that do not lower the energy of the system. In this work, we present a unitary selective coupled-cluster method, a way to construct a unitary coupled-cluster ansatz iteratively using a selection procedure with excitations up to fourth order. This approach uses the electronic Hamiltonian matrix elements and the amplitudes for excitations already present in the ansatz to find the important excitations of higher order and to add them to the ansatz. The important feature of the method is that it systematically reduces the energy error with increasing ansatz size for a set of test molecules. {The main advantage of the proposed method is that the effort to increase the ansatz does not require any additional measurements on a quantum computer.}
- Research Organization:
- General Atomics, San Diego, CA (United States)
- Sponsoring Organization:
- USDOE Laboratory Directed Research and Development (LDRD) Program; USDOE Office of Science (SC); USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF); USDOE Office of Science (SC), Fusion Energy Sciences (FES)
- Grant/Contract Number:
- AC02-06CH11357; SC0020249
- OSTI ID:
- 1996551
- Journal Information:
- Quantum, Journal Name: Quantum Vol. 6; ISSN 2521-327X
- Publisher:
- Quantum Science Open CommunityCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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