Russian researchers have developed an experimental superconducting quantum processor capable of performing complex three-qubit logical operations with an accuracy of 99.39%, setting a new world record for this type of quantum gate. The National University of Science and Technology MISIS (NUST MISIS) has announced a milestone demonstrating a new method to quantum computing. This approach has the potential to increase the scalability of future quantum computers, simplify processor architecture, and reduce computational errors.
The processor demonstrated the capacity to directly execute a three-qubit CCZ logical operation, rather than constructing it through a sequence of simpler operations, and uses superconducting qubits known as fluxoniums. The operation is completed in a mere 65 nanoseconds with a single microwave pulse, which greatly decreases the number of computational steps necessary.
This study was conducted by scientists from the Moscow Institute of Physics and Technology (MIPT), the Russian Quantum Center (RQC), the Institute of Microelectronics Technology and High-Purity Materials of the Russian Academy of Sciences (IMT RAS), and NUST MISIS. The findings are a major development in the field of superconducting quantum processor technology, particularly in the context of multi-qubit operations.
A New Approach to Three-Qubit Quantum Operations
One central challenge in developing practical quantum computers is performing intricate logical operations with high precision. Unlike conventional computers, which use binary bits to process information, quantum computers use quantum bits, or qubits, that can exist in different states.
Quantum algorithms often require operations that involve multiple qubits operating simultaneously. The CCZ gate, which stands for Controlled-Controlled-Z, is an example of such an operation. It is a three-qubit quantum gate that implements a controlled phase change in accordance with the sum of the three qubits’ states.
CCZ gates are critical components of numerous quantum computing applications, such as quantum algorithms, queries involving unstructured datasets, mathematical factorization, and quantum error-correction systems.
Traditionally, implementing a CCZ operation requires breaking it down into a sequence of eight two-qubit operations. Despite the effectiveness of this method, each additional operation introduces another opportunity for errors. The quantum processor’s overall reliability is compromised as these errors accumulate during the computation process.
This limitation has been resolved by demonstrating that the three-qubit operation can be executed directly using a single microwave control pulse. This eliminates the necessity of executing the conventional sequence of eight two-qubit gates.
Fluxonium Qubits Form the Foundation
The processor is composed of three superconducting fluxonium qubits that are connected by a shared transmon coupler. This configuration enables the researchers to regulate the interactions between the three quantum memory elements using microwave signals.
Fluxonium is a specialized form of superconducting qubit engineered to provide improved coherence properties. Quantum coherence is the capacity of a quantum system to maintain its quantum state before the loss of information due to environmental disturbances and other sources of noise.
One of the advantages of fluxonium is its ability to maintain quantum information for longer periods compared with several other superconducting qubit architectures. This makes it an attractive candidate for quantum processors that require increasingly complex calculations.
However, fluxonium technology has historically presented manufacturing and control challenges. It necessitates sophisticated fabrication processes and meticulously devised control techniques due to its more intricate structure than conventional transmon qubits.
Russian researchers have devoted several years to resolving these constraints. Their advancements in manufacturing fluxonium devices and regulating their behavior established the technological foundation for the most recent three-qubit processor experiment.
The shared transmon coupler plays an important role in the architecture. The researchers use the coupler to enable controlled interactions between the three fluxonium qubits, rather than directly connecting them through a conventional arrangement. This enables the implementation of the necessary multi-qubit operation while simultaneously restricting unwanted interactions in other areas of the processor.
A New Experimental Record: 99.39% Accuracy
The accuracy obtained during the execution of the CCZ operation is the most significant outcome of the experiment. The researchers achieved a record fidelity of 99.39% for this category of three-qubit logical gates.
Ilya Simakov, a researcher at NUST MISIS, said that the conventional approach would necessitate individual two-qubit gates operating with a fidelity of approximately 99.94% to achieve comparable accuracy.
Even for the most sophisticated superconducting quantum processors, this is an exceptionally demanding requirement. Hence, the Russian approach provides an alternative: it directly executes the entire three-qubit operation rather than relying on a series of highly accurate operations executed sequentially.
In addition, the experiment illustrated that the new gate does not necessitate a wholly distinct control system. A single 65-nanosecond microwave pulse is used in the operation. Its calibration is dependent on conventional methods that use Rabi and Ramsey oscillations, which are often implemented to characterize and regulate superconducting qubits.
This is important because a new quantum operation is beneficial not only when it achieves high fidelity but also when it can be implemented without incurring excessive complexity in the processor’s control architecture.
From Theoretical Calculations to Experimental Demonstration
The latest result is a continuation of the Russian team’s prior theoretical research. Approximately two years ago, researchers explored the possibility of directly executing a CCZ operation using three fluxonium qubits and a conventional superconducting transmon element.
Their theoretical calculations suggested that the operation could potentially be executed in approximately 45 nanoseconds.
The underlying principle has been demonstrated by the latest experiment, which used an actual three-qubit processor. The operation was experimentally measured had a fidelity of 99.39% and a duration of 65 nanoseconds.
The scientists’ ability to use the same general principles of microwave pulse formation that are used in conventional two-qubit operations is a critical aspect of the research. This minimizes the necessity for intricate control procedures and renders the approach more feasible for integration into larger quantum computing systems.
The research paper, “Native CCZ Gate with Fluxonium Qubits and a Microwave-Driven Coupler,” was published on the arXiv scientific preprint repository in July 2026. In this section, the performance characteristics and experimental implementation of the new processor architecture are detailed.
Implications for Scaling Quantum Computers
The significance of the development extends beyond the performance of a single three-qubit operation. Scaling processors from relatively small experimental devices to systems containing much larger numbers of interconnected qubits is one of the greatest challenges that quantum computing manufacturers face.
As the number of qubits increases, controlling interactions between them becomes increasingly complicated. Parasitic interactions, which are unwanted interactions, can introduce errors and disrupt calculations.
The Russian researchers believe that their architecture can be seamlessly integrated into a two-dimensional quantum processor layout, while simultaneously preserving mechanisms that are intended to suppress these undesirable interactions.
The number of individual gates necessary to execute complex quantum algorithms could also be reduced through direct multi-qubit operations. By reducing the number of operations, there are fewer opportunities for errors to accumulate, which has the potential to enhance computational efficiency and reduce the overhead associated with quantum error correction.
Therefore, the capacity to integrate high-fidelity operations with relatively simple microwave control is especially pertinent to the advancement of larger superconducting quantum processors.
Nevertheless, the device that was demonstrated is an experimental three-qubit processor module, rather than a fully functional, large-scale quantum computer. Additional research will be required to establish that the architecture can preserve its functionality when integrated into systems that are significantly larger.
Russia Advances Its Superconducting Quantum Computing Programme
The achievement also underscores the developments being made by Russian research institutions in the development of domestic quantum computing technologies.
The Russian Ministry of Science and Higher Education is supporting the initiative through the Priority-2030 program, which is being implemented under NUST MISIS’s strategic technological program, Quantum Internet. The initiative is a component of Russia’s overarching national initiative to cultivate sophisticated scientific and technological capabilities.
In conclusion,
A new quantum processor based on fluxonium developed by Russia illustrates the potential of direct three-qubit operations to enhance accuracy and decrease computational complexity. The experiment offers a promising foundation for the development of larger superconducting quantum processors, with an execution time of 65 nanoseconds and a CCZ gate fidelity of 99.39%. The subsequent obstacle will be the conversion of this experimental performance into scalable quantum computing architectures.