Minimum measurements quantum protocol for band structure calculation

TL;DR

This paper introduces a quantum measurement protocol for band structure calculations that reduces measurement settings to three, independent of qubit number, leveraging symmetries in Hamiltonians to improve efficiency.

Contribution

The authors develop a symmetry-based measurement protocol that significantly decreases the number of measurement configurations needed in quantum electronic structure calculations.

Findings

Protocol reduces measurement settings to three, regardless of qubit count.

Demonstrated on systems with 3 and 4 qubits, showing practical feasibility.

Potential to extend to complex many-body Hamiltonians with high symmetry.

Abstract

Protocols for quantum measurement are an essential part of quantum computing. Measurements are no longer confined to the final step of computation but are increasingly embedded within quantum circuits as integral components of noise-resilient algorithms. However, each observable typically requires a distinct measurement basis, often demanding a different circuit configuration. As the number of such configurations typically grows with the number of qubits, different measurement configurations constitute a major bottleneck. Focusing on electronic structure calculations in crystalline systems, we propose a measurement protocol that maximally reduces the number of measurement settings to just three, independent of the number of qubits. This makes it one of the few known protocols that do not scale with qubit number. In particular, we derive the measurement protocol from the symmetries of tight-binding (TB) Hamiltonians and implement it within the Variational Quantum Deflation (VQD) algorithm. We demonstrate its performance on two systems, namely a two-dimensional CuO$_2$ square lattice (3 qubits) and bilayer graphene (4 qubits). The protocol can be generalized to more complex many-body Hamiltonians with high symmetry, providing a potential path toward future demonstrations of quantum advantage.