RIKEN circuit design cuts quantum simulation depth by 10×, Q-CTRL reports

A tenfold reduction in quantum simulation circuit depth has enabled researchers at RIKEN to surpass previous limitations in modeling complex quantum systems. The Computational Quantum Matter research team at RIKEN partnered with Q-CTRL to simulate open system dynamics on quantum hardware from IBM and Quantinuum, achieving this advance through optimized circuit design and the deployment of Fire Opal error suppression software. The team utilized breaking down environmental interactions into a sequence of brief exchanges with auxiliary systems. “Q-CTRL played a key role in extending our quantum collision-model simulations of Markovian quantum processes on IBM superconducting hardware,” said Seiji Yunoki, Chief Scientist & Team Leader at RIKEN Center for Computational Science, explaining that their expertise and Fire Opal software helped achieve simulations beyond previously demonstrated scales.

Collisional Models Simulate Open Quantum System Dynamics

Unlike isolated quantum systems, open systems experience energy loss and dissipation, phenomena critical to modeling natural processes but computationally expensive to simulate. This discrete approach effectively reproduces the memoryless dynamics induced by the environment, allowing for implementation on digital quantum computers through specifically designed circuits. These circuits utilize data qubits interacting with ancillary qubits, frequently measured and reset to simulate non-unitary evolution; however, the numerous mid-circuit measurements historically resulted in extremely deep circuits, a significant hurdle for superconducting qubits with limited coherence times. Optimizing circuit design for the hardware platform proved essential, and Q-CTRL assisted RIKEN in redesigning circuits for IBM’s superconducting architecture. A key innovation was the deployment of a strategy leveraging the abundance of qubits on IBM hardware to utilize pristine qubits rather than recycling them after each interaction. Following this structural redesign, Q-CTRL’s Fire Opal error suppression software further enhanced performance.

Fire Opal, an AI-driven tool, optimizes circuit execution and shields the system from hardware imperfections without requiring user intervention or hardware modifications. “Their hardware-aware execution expertise, together with Fire Opal’s error-management software, helped us achieve long-time simulations beyond previously demonstrated scales.” The resulting hardware-aware design, paired with Fire Opal compilation, reduced two-qubit gate depth by approximately an order of magnitude, enabling a seven-qubit quantum collision model to run for up to 40 time steps.

Accurately representing these real-world phenomena demands substantial computational resources, historically limiting the scale of such simulations. The team employed a collisional model to represent environmental interactions, a technique that breaks down the environment into a series of brief interactions with auxiliary systems before they are reset.