Applications of quantum computing for investigations of electronic transitions in phenylsulfonyl-carbazole TADF emitters

Qi Gao,Naoki Yamamoto,Michihiko Sugawara,Hajime Nakamura,Eriko Watanabe,Hiroshi C Watanabe,Gavin O Jones,Takao Kobayashi,Yu-Ya Ohnishi,Mario Motta

doi:10.1038/s41524-021-00540-6

Abstract

A quantum chemistry study of the first singlet (S1) and triplet (T1) excited states of phenylsulfonyl-carbazole compounds, proposed as useful thermally activated delayed fluorescence (TADF) emitters for organic light emitting diode (OLED) applications, was performed with the quantum Equation-Of-Motion Variational Quantum Eigensolver (qEOM-VQE) and Variational Quantum Deflation (VQD) algorithms on quantum simulators and devices. These quantum simulations were performed with double zeta quality basis sets on an active space comprising the highest occupied and lowest unoccupied molecular orbitals (HOMO, LUMO) of the TADF molecules. The differences in energy separations between S1 and T1 (ΔEST) predicted by calculations on quantum simulators were found to be in excellent agreement with experimental data. Differences of 17 and 88 mHa with respect to exact energies were found for excited states by using the qEOM-VQE and VQD algorithms, respectively, to perform simulations on quantum devices without error mitigation. By utilizing state tomography to purify the quantum states and correct energy values, the large errors found for unmitigated results could be improved to differences of, at most, 4 mHa with respect to exact values. Consequently, excellent agreement could be found between values of ΔEST predicted by quantum simulations and those found in experiments.

Highlights

One of the major constraints of modern electronic structure methods used for quantum chemical calculations on classical computing architecture is the difficulty of finding eigenvalues of eigenvectors of the electronic Hamiltonian[1].The advent of quantum computing, which has demonstrated tremendous synergistic advances in both hardware and software capabilities in recent years, may provide invaluable support in the investigation of the electronic structure of molecules and materials, especially with regards to dynamical properties
This conclusion is further bolstered by the fact that the application of quantum state tomography techniques to ground states predicted by Variational Quantum Eigensolver (VQE) resulted in excellent agreement between computational predictions of ΔEST and experiments for all the examined PSPCz molecules. These results indicate that the best results are obtained by applying quantum state tomography techniques to the ground state computed with VQE and applying readout error mitigation to the measurements of the matrix elements of the EOM for qEOM-VQE computations of excited states
The excited energies were predicted to differ from exact values by as much as 16 and 88 mHa by simulations performed with the qEOM-VQE and Variational Quantum Deflation (VQD) algorithms, respectively

Summary

INTRODUCTION

One of the major constraints of modern electronic structure methods used for quantum chemical calculations on classical computing architecture is the difficulty of finding eigenvalues of eigenvectors of the electronic Hamiltonian[1]. We have reduced the number of spatial orbitals to those functional theory (DFT) has previously been utilized to help guide that are absolutely necessary to describe the processes under the design of TADF emitters by calculating the efficiency and emission spectrum of potential TADF materials[14,15,16,17,18,19], the accuracy investigation and have focused on transitions involving the HOMO and LUMO active space for each molecule (Fig. 2)[21] This of DFT methods for such simulations can be quite limited in some strategy has allowed reduction of the number of required qubits cases. This procedure can be repeated to compute further higher excited

RESULTS AND DISCUSSION

METHODS

CODE AVAILABILITY