Issue 62, 2021

A systematic variational approach to band theory in a quantum computer


Quantum computers promise to revolutionize our ability to simulate molecules, and cloud-based hardware is becoming increasingly accessible to a wide body of researchers. Algorithms such as Quantum Phase Estimation and the Variational Quantum Eigensolver are being actively developed and demonstrated in small systems. However, extremely limited qubit count and low fidelity seriously limit useful applications, especially in the crystalline phase, where compact orbital bases are difficult to develop. To address this difficulty, we present a hybrid quantum-classical algorithm to solve the band structure of any periodic system described by an adequate tight-binding model. We showcase our algorithm by computing the band structure of a simple-cubic crystal with one s and three p orbitals per site (a simple model for polonium) using simulators with increasingly realistic levels of noise and culminating with calculations on IBM quantum computers. Our results show that the algorithm is reliable in a low-noise device, functional with low precision on present-day noisy quantum computers, and displays a complexity that scales as Ω(M3) with the number M of tight-binding orbitals per unit-cell, similarly to its classical counterparts. Our simulations offer a new insight into the “quantum” mindset and demonstrate how the algorithms under active development today can be optimized in special cases, such as band structure calculations.

Graphical abstract: A systematic variational approach to band theory in a quantum computer

Article information

Article type
07 Oct 2021
01 Dec 2021
First published
10 Dec 2021
This article is Open Access
Creative Commons BY license

RSC Adv., 2021,11, 39438-39449

A systematic variational approach to band theory in a quantum computer

K. Sherbert, F. Cerasoli and M. Buongiorno Nardelli, RSC Adv., 2021, 11, 39438 DOI: 10.1039/D1RA07451B

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