Convergence of Supercomputers and Quantum Computers Breaks the 12,000-Atom Barrier... A New Milestone in Drug Discovery
inquantio
Abstract
A study published on the preprint repository arXiv expanded the existing system scale by more than 40 times by combining quantum embedding technology, which decomposes a molecule into multiple fragments, with a heterogeneous quantum-classical (HQC) computing method. Utilizing two 156-qubit quantum processors (ibm_cleveland, ibm_kobe) and two supercomputers (Fugaku, Miyabi-G), the research successfully simulated the quantum chemistry of protein-ligand complexes consisting of more than 12,000 atoms. The HQC method matched the accuracy level of the classical coupled-cluster (CCSD) method in fragment energies, proving its practical, industrial-scale potential to drastically reduce the time and cost of the drug discovery pipeline. [Quantum Biology Society] Predicting the interaction between a target protein and a drug candidate is crucial in drug discovery, but simulating its fundamental quantum mechanical structure could previously only be applied to extremely small-scale systems due to limitations in computational scale. However, a recent study successfully and accurately simulated complex protein-ligand complexes consisting of over 12,000 atoms through "heterogeneous quantum-classical (HQC) computing," which combines quantum computers with classical supercomputers, drawing the attention of the global pharmaceutical and IT industries. The study, "Crossing the 12,000-atom barrier with heterogeneous quantum-classical supercomputing: quantum chemistry of protein-ligand complexes," published on the preprint repository arXiv, was conducted by a multinational joint research team. This included Kenneth M. Merz, Jr.'s research team at the Cleveland Clinic Foundation in the U.S., Yuichi Otsuka and Tomonori Shirakawa's research teams at RIKEN in Japan, and researchers from IBM Quantum. ■ Splitting Molecules with 'Quantum Embedding' and Combining them with 'Supercomputers' The core of this massive calculation is "quantum embedding" technology. Instead of calculating the entire giant protein molecule at once, the method decomposes the molecule into multiple smaller fragments and simulates each independently. The research team executed 9,200 quantum circuits for over 100 hours, utilizing up to 94 qubits across two 156-qubit quantum processors (ibm_cleveland, ibm_kobe), and collected 1.3×10⁹ measurement outcomes. This is the most resource-intensive HQC computation performed in the field of quantum chemistry to date. Simultaneously, they mobilized Japan's world-class supercomputers, Fugaku and Miyabi-G, to perform subspace diagonalization via scalable distributed linear algebra kernels, achieving a high parallel efficiency of 72.5%. ■ System Size Expanded by 40x, Accuracy Improved by up to 210x Through this innovative workflow, the research team successfully simulated two giant protein-ligand complexes spanning dispersion- and electrostatics-dominated regimes (comprising 11,608 and 12,635 atoms, respectively). As a result, compared to previous state-of-the-art technologies, they achieved the feat of expanding the size of the simulatable system by more than 40 times and improving computational accuracy by up to 210 times. In particular, it is highly encouraging that the HQC method reached the high accuracy of the classical coupled-cluster (CCSD) level in fragment energy calculations. This achievement establishes a scalable pathway for systematically improvable biomolecular simulations, demonstrating the potential to drastically reduce the time and massive costs of the drug discovery pipeline through accurate characterization of drug-protein complexes. Experts evaluate this study as a crucial milestone showing that the technology to explore small-molecule hit substances for target proteins using actual quantum computers can be implemented on a real industrial scale, moving well beyond the laboratory level. https://arxiv.org/abs/2605.01138v1