Engineers in Japan have completed the activation of the world’s first hybrid quantum supercomputer, called Reimei. The quantum computer has 20 qubits and is integrated into Fugaku, the sixth fastest supercomputer in the world. This innovative platform is expected to offer significant advantages in performing calculations that take a long time on traditional supercomputers.
The Reimei hybrid quantum computer will be used primarily for research purposes in physics and chemistry. It is located at the Riken Institute of Science, located in Saitama, near Tokyo. Representatives from Riken and Quantinuum, the company that built Reimei, have stated that this platform will allow solving complex problems that classical computers cannot handle effectively.
According to information from LiveScience, quantum computers have the potential to replace traditional computers in the future. This is because they can complete calculations in minutes or seconds, while today’s most powerful computers would take millions of years to achieve the same results. This development could significantly impact various fields of science and technology.
What are qubits?
Here, let’s take a brief parenthesis to explain what qubits are in quantum computers. The memory of a classical digital computer consists of bits that can represent the value 1 or 0. In quantum computers, however, we have qubits. A qubit can represent the value 1, 0, or any superposition of these 2.
Two qubits can represent any superposition of four possible states, 3 qubits any superposition of 8 states. In general, a quantum computer with n qubits can be in an arbitrary superposition of up to 2n possible states simultaneously, while a classical computer can only be in one of these states at any time. This results in an incredible acceleration of processing power.
The difference between Reimei and other quantum computers
Unlike most quantum computers that use superconducting qubits, Reimei uses trapped-ion qubits. This involves isolating charged atoms, or ions, in an electromagnetic field – known as an ion trap – and using lasers to precisely control their quantum state.
This allows scientists to manipulate the ions so that they can be used as qubits that store and process quantum information. Trapped-ion qubits encourage more connections between qubits and longer coherence times, while superconducting qubits have faster gate connections and are easier to fabricate on a chip.
Riken officials said they chose Quintinuum’s quantum computer for the integration because it has a unique architecture that physically moves the qubits. This process of “ion-hopping” allows qubits to be moved around a circuit as needed, enabling more complex algorithms.
Error-correction system
Qubits are inherently “noisy,” so to effectively scale quantum computers, scientists are developing error-correction techniques to increase the fidelity of the qubits.
At Reimei, physical ion qubits are grouped together to create “logical qubits”—that is, a set of physical qubits that store the same information in different places. Logical qubits are a key way to achieve the desired reduction in qubit errors because distributing information across different places spreads out the points of failure, meaning that a qubit failure does not disrupt an ongoing calculation.
Quaintinuum previously achieved a breakthrough by creating a logical qubit with an error rate 800 times lower than physical qubits, which it integrated into its quantum computer processors.
Yet another hybrid system
While Reimei-Fugaku is the first fully operational, integrated hybrid system, other companies have tested such systems in the past. In June 2024, IQM integrated a 20-qubit quantum processor into the SuperMUC-NG supercomputer in Garching, Germany.
This system, however, is still in the testing phase, with no publicly confirmed date for when it will become fully operational. In October, IQM representatives announced that the company would integrate a 54-qubit system into the supercomputer in the second half of 2025, followed by a 150-qubit chip in 2026.
