Molecular Structure Optimization Based on Electrons–Nuclei Quantum Dynamics Computation

Abstract

A new concept of the molecular structure optimization method based on quantum dynamics computations is presented. Nuclei are treated as quantum mechanical particles, as are electrons, and the many-body wave function of the system is optimized by the imaginary time evolution method. The numerical demonstrations with a two-dimensional H 2 + system and a H–C–N system exemplify two possible advantages of our proposed method: (1) the optimized nuclear positions can be specified with a small number of observations (quantum measurements) and (2) the global minimum structure of nuclei can be obtained without starting from any sophisticated initial structure and getting stuck in the local minima. This method is considered to be suitable for quantum computers, the development of which will realize its application as a powerful method.

Grid-based methods for chemistry simulations on a quantum computer

“…We refer the reader to the Supplementary Materials for a detailed presentation of these topics. We highlight that this method of exploiting quantum computers, explored by earlier authors in ( 5 – 8 , 10 – 12 , 16 , 17 ), is an adaption of the classical computing methods developed in ( 30 , 58 – 60 ), which we also review in the Supplementary Materials.…”

“…In this work, we investigate the prospects for accelerating chemical dynamics simulation on early fault-tolerant quantum computers using the first-quantized, real-space grid approach (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17). By "early," we mean machines that have a limited number of error-corrected qubits, as we presently explain.…”

Statistical errors in reduced density matrices sampled from quantum circuit simulation and the impact on multireference perturbation theory

“…Simulation of the Hamiltonian for strongly entangled quantum systems is widely regarded as a promising application [10][11][12][13][14][15][16][17][18] in both noisy intermediate-scale quantum (NISQ) devices [19][20][21][22][23][24] and fault-tolerant quantum computers (FTQC), [25][26][27][28] which has the potential to enable calculations for large CAS wavefunctions that are difficult to achieve with classical computers. By associating an electronic configuration in the active space with an eigenstate of qubits, it is possible to map a CAS wavefunction onto a superposition state of qubits; the required number of qubits is equal to the number of spin-orbitals in the active space.…”