April 1, 2026 by University of Osaka
Collected at: https://phys.org/news/2026-04-world-largest-quantum-circuit-simulation.html
A joint research team between the Center for Quantum Information and Quantum Biology (QIQB) at The University of Osaka and Fixstars Corporation has demonstrated one of the world’s largest classical simulations of iterative quantum phase estimation (IQPE) circuits for quantum chemistry on up to 1,024 GPUs, surpassing the previous 40-qubit limit. The result expands the scale of molecular systems available for the development and validation of quantum algorithms for future fault-tolerant quantum computers, supporting progress toward industrial applications in drug discovery and materials development.
The paper was presented at NVIDIA GTC 2026, held in San Jose, California, March 16–19, 2026.
Overcoming unresolved challenges in drug discovery and developing new materials to address climate change will require advanced quantum chemical calculations beyond the reach of current technology. Against this backdrop, fault-tolerant quantum computers (FTQC) are widely anticipated as a key enabling technology, making it increasingly important to develop and validate, ahead of their deployment, the quantum algorithms that will eventually run on such systems.
Quantum phase estimation (QPE) serves as a core subroutine in many quantum algorithms and, in quantum chemistry, is expected to enable analyses that are difficult for current classical computers. The research group, consisting of Professor Wataru Mizukami, Assistant Technical Staff Shoma Hiraoka, and Assistant Technical Staff Sho Nishida at QIQB, and Yusuke Teranishi of Fixstars Corporation, focused on Iterative QPE (IQPE), a QPE-based method that requires fewer qubits, and implemented it in the quantum circuit simulator for quantum chemistry, “chemqulacs-gpu.”
The group also developed and applied a new parallel computing technology to maximize the performance of large-scale GPU clusters. As a result, they exceeded the previous limit of 40 qubits for state-vector-based quantum circuit simulations for quantum chemistry reported in earlier studies and successfully carried out one of the world’s largest such simulations.
The simulations achieved the following results:
- Largest problem size: calculation of a 42-spin-orbital system for an H₂O molecule (with qubit reduction technology applied)
- Largest circuit size: calculation of a 41-qubit circuit for an Fe₂S₂ molecule (pure circuit-scale benchmark)
To achieve this result, the team implemented IQPE in the quantum chemistry simulator “chemqulacs-gpu” and developed a parallel computing method optimized for large-scale GPU clusters. Using up to 1,024 NVIDIA H100 GPUs on AIST’s ABCI-Q system, the researchers overcame conventional computational bottlenecks and extended quantum circuit simulations of quantum algorithms for quantum chemistry beyond the previous 40-qubit limit.
This achievement expands the range of molecules that can be targeted in the development and validation of quantum algorithms and supports further progress toward more complex and realistic molecular simulations on future fault-tolerant quantum computers.
Professor Wataru Mizukami says, “Large-scale simulation of quantum circuits using 1,024 GPUs in unison is technically demanding, and within the limited 48-hour computation window we repeatedly encountered unexpected issues.
“I am delighted that the team, led by two young researchers, Yusuke Teranishi and Shoma Hiraoka, persevered throughout the effort, and that, with prompt support from the ABCI-Q operations staff, we were able to achieve one of the world’s largest results. I hope this accomplishment will help accelerate the development of quantum algorithms.”
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