Abstract
We propose a scheme for the construction of charge and spin linear-response functions of an interacting electronic system via quantum phase estimation and statistical sampling on a quantum computer. By using the unitary decomposition of electronic operators for avoiding the difficulty due to their non-unitarity, we provide the circuits equipped with ancillae for probabilistic preparation of qubit states on which the necessary non-unitary operators have acted. We perform simulations of such construction of the response functions for C2 and N2 molecules by comparing with the accurate ones based on the full configuration interaction calculations. It is found that the accurate detection of subtle structures coming from the weak poles in the response functions requires a large number of measurements.
Highlights
Since the information carrier of a programmable quantum computer is a set of qubits that exploits the principle of superposition, essentially parallel algorithms can exist and perform computation for classically formidable problems [1,2]
We proposed a scheme for the construction of linearresponse functions of an interacting electronic system via quantum phase estimation (QPE) and statistical sampling on a quantum computer
By using the unitary decomposition of electronic operators for avoiding the difficulty due to their nonunitarity, we provided the circuits equipped with at most three ancillae for probabilistic preparation of qubit states on which the necessary nonunitary operators have acted
Summary
Since the information carrier of a programmable quantum computer is a set of qubits that exploits the principle of superposition, essentially parallel algorithms can exist and perform computation for classically formidable problems [1,2]. The quantity which a quantum chemistry calculation is asked to first provide is the total energy of a target system [6]. The parameters are optimized iteratively with the aid of a classical computer aiming at the ground state. This approach was first realized [7] by using a quantum photonic device, after which the realizations by superconducting [8,9] and ion trap [10] quantum computers have been reported. There exist algorithms for obtaining the energy spectra of excited states [11,12,13,14,15,16]
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