We develop an energy calculation algorithm leveraging quantum phase difference estimation (QPDE) scheme and a tensor-network-based unitary compression method in the preparation of superposition states and time-evolution gates. Alongside its efficient implementation, this algorithm reduces depolarization noise affections exponentially. We demonstrated energy gap calculations for one-dimensional Hubbard models on IBM superconducting devices using circuits up to 32-system (plus one-ancilla) qubits, a five-fold increase over previous QPE demonstrations, at the 7242 controlled-Z gate level of standard transpilation, utilizing a Q-CTRL error suppression module. Additionally, we propose a technique towards molecular executions using spatial orbital localization and index sorting, verified linear polyene simulations up to 21 qubits. Since QPDE can handle the same objectives as QPE, our algorithm represents a leap forward in quantum computing on real devices.
@article{arxiv.2408.04946,
title = {Tensor-based quantum phase difference estimation for large-scale demonstration},
author = {Shu Kanno and Kenji Sugisaki and Hajime Nakamura and Hiroshi Yamauchi and Rei Sakuma and Takao Kobayashi and Qi Gao and Naoki Yamamoto},
journal= {arXiv preprint arXiv:2408.04946},
year = {2025}
}