New Quantum Computer in Japan: IBM and RIKEN unveil a highly powerful system

IBM and the Japanese research institute RIKEN have jointly commissioned the first IBM Quantum System Two outside the United States and beyond an IBM-owned data center. This event, celebrated with a formal ceremony on June 24, 2025, is also particularly significant because the new quantum computer was installed directly next to Fugaku, one of the world’s most powerful classical supercomputers. The collaboration is set to lead Japan into a new era of high-performance computing.

At the heart of the IBM Quantum System Two is an IBM Quantum Heron processor with 156 qubits. According to IBM, it is currently the world’s most powerful quantum processor. Its performance is defined not only by the number of qubits but also by its processing speed. Measured by the CLOPS metric (Circuit Layer Operations Per Second), Heron achieves a value of 250,000, which is a tenfold increase over the previous generation, the IBM Quantum Eagle.

A crucial factor for the practical viability of quantum computers is the error rate. Quantum bits (qubits) use sensitive quantum physical phenomena such as entanglement and superposition to perform calculations. However, these states are extremely susceptible to disturbances from their environment. Even the slightest influences can alter the quantum states and thus lead to calculation errors, which often also severely shortens the operating time of the qubits (runtimes). With each additional qubit in a quantum computer, the susceptibility to such errors potentially increases. A high error rate therefore poses a challenge to scalability and reliability, as it can render the results useless. Effective error correction systems are therefore essential to control errors despite the increasing complexity of a system.

This is where the technological improvement of the Heron processor comes in: its two-qubit error rate is 3 times 10 to the power of -3 in a 100-qubit circuit, with a best value of 1 times 10 to the power of -3, representing a tenfold improvement over the earlier IBM Quantum Eagle. This significantly improved error rate is an important step towards more reliable quantum computations. The coupling of the IBM Quantum System Two with the supercomputer Fugaku at the RIKEN Center for Computational Science (R-CCS) creates a unique testbed for so-called “quantum-centric supercomputing.” Through a high-speed connection at a fundamental command level, RIKEN and IBM engineers can develop parallelized workflows, low-latency communication protocols, and advanced compilation libraries. This integration is of great importance because quantum and classical systems have different strengths and can thus seamlessly execute the parts of an algorithm for which they are best suited. The goal is to enable groundbreaking research, for example on fundamental problems in chemistry, and ultimately to reach the point of “quantum advantage,” where a quantum computer can solve a problem faster, more cost-effectively, or more accurately than any known classical method.