Osaka and Fixstars Simulated a 40-Qubit Quantum Circuit. They Did It on Classical GPUs.

Osaka University and Fixstars simulated quantum chemistry circuits (up to 41 qubits) using 1,024 NVIDIA H100 GPUs, claiming the largest classical simulation for quantum chemistry applications. The 40-qubit figures refer to simulated circuit depth/size, not physical qubits in a quantum processor—a critical distinction that media coverage has repeatedly conflated. This is a legitimate classical HPC achievement useful for algorithm development and verification, but it provides no direct insight into actual quantum hardware capabilities.

• •The '40-qubit barrier' refers to simulated circuit size, not physical qubits—these metrics measure fundamentally different things and should not be conflated
• •Classical simulations of quantum circuits are valuable for algorithm development and verification but do not represent quantum hardware milestones
• •The largest chemistry problem was a 42-spin-orbital system for H₂O using iterative quantum phase estimation (IQPE)