Emergent-Coupling-Based Ansatz Evaluated on a Superconducting Quantum Processor

TL;DR

This paper experimentally evaluates the emergent-coupling-based ansatz (ECBA) for variational quantum eigensolvers on superconducting processors, demonstrating high accuracy and efficient embedding for disordered systems.

Contribution

It introduces and benchmarks the ECBA, a physically motivated ansatz based on renormalization group ideas, showing improved accuracy over standard methods on quantum hardware.

Findings

Achieved 96.47% relative energy accuracy for 30-qubit systems.

ECBA can be efficiently embedded on 2D square-lattice hardware.

Outperforms common hardware-efficient ans"atze in accuracy at similar gate counts.

Abstract

The performance of the variational quantum eigensolver depends critically on the choice of ansatz. In this work, we experimentally evaluate the emergent-coupling-based ansatz (ECBA), a physically motivated variational ansatz for disordered systems. The ECBA is based on a renormalization (semi-)group approach to determine the dominant effective couplings, resulting in shallow circuits that capture the essential long-range entanglement structure while balancing local correlations. We implement the ECBA on superconducting quantum processors and benchmark it on disordered Heisenberg chain models. Using classically pre-optimized parameters and error mitigation techniques, we study systems of up to 30 qubits and observe an experimental relative energy accuracy of 96.47% for the largest system. Furthermore, we find that the ECBA can be efficiently embedded on hardware with two-dimensional square-lattice connectivity. We compare to commonly used hardware efficient ans\"atze and observe that the ECBA achieves significantly higher accuracy at a similar gate count.