Optimization of the variational quantum eigensolver for quantum chemistry applications
Year: 2022
Authors: de Keijzer RJPT., Colussi VE., Skoric B., Kokkelmans SJJMF.
Autors Affiliation: Eindhoven Univ Technol, POB 513, NL-5600 MB Eindhoven, Netherlands; Univ Trento, CNR, BEC Ctr, INO, I-38123 Povo, Italy; Univ Trento, Dipartimento Fis, I-38123 Povo, Italy.
Abstract: This work studies the variational quantum eigensolver (VQE) algorithm, which is designed to determine the ground state of a quantum mechanical system by combining classical and quantum hardware. Two methods of reducing the number of required qubit manipulations, prone to induce errors, for the variational quantum eigensolver are studied. First, we formally justify the multiple Z(2) symmetry qubit reduction scheme first sketched by Bravyi et al. [arXiv:1701.08213 (2017)]. Second, we show that even in small, but non-trivial systems such as H-2, LiH, and H2O, the choice of entangling methods (gate based or native) gives rise to varying rates of convergence to the ground state of the system. Through both the removal of qubits and the choice of entangler, the demands on the quantum hardware can be reduced. We find that in general, analyzing the VQE problem is complex, where the number of qubits, the method of entangling, and the depth of the search space all interact. In specific cases however, concrete results can be shown, and an entangling method can be recommended over others as it outperforms in terms of difference from the ground state energy.
Journal/Review: AVS QUANTUM SCIENCE
Volume: 4 (1) Pages from: 13803-1 to: 13803-10
More Information: We thank Jasper Postema and Gijs Groeneveld for discussions. This research is financially supported by the Dutch Ministry of Economic Affairs and Climate Policy (EZK), as part of the Quantum Delta NL programme, and by the Netherlands Organisation for Scientific Research (NWO) under Grant Nos. 680-47-623 and 680-92-18-05.DOI: 10.1116/5.0076435Connecting to view paper tab on IsiWeb: Click here
