A groundbreaking milestone in quantum computing has been reached by the SPINNING project, funded by the German Federal Ministry for Research, Technology, and Space (BMFTR). This ambitious three-year initiative has unveiled a distributed, hybrid-integrable solid-state quantum computer system based on diamond spin qubits, poised to redefine the future of scalable quantum architectures. Diverging from the conventional reliance on superconducting qubits, SPINNING’s approach utilizes spin-photon interactions in diamond, creating a pathway toward room-temperature operation, extended coherence times, and impressive error minimization. This technology offers a promising alternative in the global race for practical and energy-efficient quantum computing solutions.
At the heart of SPINNING’s innovation lies the synthesis and manipulation of spin qubits hosted in color centers within diamond substrates. These color centers—primarily nitrogen vacancy (NV), germanium vacancy (GeV), and tin vacancy (SnV) defects—serve as robust quantum bits that maintain coherence far beyond what is typical for superconducting Josephson junction (SJJ) based systems. By embedding these spin qubits within diamond crystals featuring a meticulously controlled nuclear spin environment, the team achieved a quieter quantum landscape, suppressing decoherence mechanisms that traditionally scramble fragile quantum states. This refined material platform is foundational for the project’s unprecedented performance metrics.
One of the most distinguishing accomplishments realized by SPINNING is the successful entanglement of two separate quantum registers, each comprising six qubits, over an impressive distance exceeding 20 meters. This feat was enabled by high-quality photonic coupling facilitated through diamond-based optical microresonators. Such long-range coupling vastly exceeds the typical scale of quantum entanglement which often occurs over micrometer or millimeter distances in superconducting architectures. Achieving an average fidelity surpassing 0.9 in state similarity, this breakthrough demonstrates an unprecedented capacity for distributed quantum operations, a vital capability for constructing more powerful quantum networks and modular computers.
The architectural design pursued by SPINNING is truly hybrid and scalable, integrating the distinct advantages of spin qubits with a photonic interconnect framework. Optical microresonators act as efficient mediators, converting quantum information between spin states and photons. These photons then carry quantum correlations across spatially separated registers, allowing seamless, coherent communication. This design not only enables scalability across tens of meters but also promises compatibility with conventional computational infrastructure, fostering a hybrid quantum-classical ecosystem essential for practical quantum computing adoption.
Technological innovation extended beyond qubit creation, encompassing major progress in diamond microresonator fabrication achieving high Q-factors, essential for minimizing optical losses and ensuring strong spin-photon coupling. Precisely positioning color centers within these microresonators necessitated cutting-edge nanofabrication techniques, optimizing spatial overlap between the qubit’s electronic spin transitions and resonator modes. Moreover, the project developed novel quantum-grade electronics to operate this hybrid quantum device, advancing control systems capable of precise timing and error mitigation—critical requirements for functional quantum computation.
SPINNING’s advancements also chart new territory in quantum error rates and coherence times surpassing leading superconducting quantum devices. The developed spin-photon quantum computer achieved single-qubit gate error rates below 0.5%, rivalling or bettering prominent SJJ-based quantum processors such as IBM’s Eagle and Heron systems, despite operating at higher temperatures and with fewer qubits currently. Most strikingly, coherence times exceeded 10 milliseconds, representing an increase by two orders of magnitude over typical superconducting qubit temporal stability measured in microseconds. This extended coherence offers increased operational windows to execute complex quantum algorithms before decoherence intervenes.
Supporting these quantum hardware leaps, software and infrastructure developments within SPINNING were pivotal. The consortium integrated firmware and control protocols tailored to the unique hybrid quantum design, enabling real-time error detection and operational optimization. The team also demonstrated practical use cases including initial applications in artificial intelligence, signaling that this technology is approaching real-world viability. The collaboration between academic and industrial partners ensured that both foundational research and applied technology pathways were concurrently advanced.
The consortium assembling this major advance combined expertise from six universities, two non-profit research institutions, and several leading SMEs and spin-offs within quantum technology fields. Spearheaded by Fraunhofer Institute for Applied Solid State Physics IAF, this multi-disciplinary alliance leveraged advances in material sciences, quantum optics, and computational methods. Their collaborative efforts were underscored by strategic funding and alignment with Germany’s federal quantum technology roadmap, securing a €16.1 million investment to drive the translation of quantum fundamentals into market-ready hardware.
In comparison to SJJ quantum computers, SPINNING’s diamond-based system holds remarkable promise for room-temperature operation or near-room-temperature regimes, effectively reducing the cryogenic infrastructure demands so prevalent in superconducting qubit systems. Such thermal resilience reduces overall system complexity, energy consumption, and the cost of scaling quantum processors. This paradigm shift could accelerate the commercialization timelines for quantum solutions, fostering wider adoption across sectors ranging from chemical simulations and cryptography to machine learning.
Beyond the technical achievements, SPINNING’s demonstration of robust entanglement spanning multiple registers and long distances lays groundwork for future quantum networks. These interconnected quantum nodes, sharing entangled states over tens of meters, form building blocks for distributed quantum computing and quantum communication protocols, vital for realizing the quantum internet. The project thus not only advances standalone quantum processors but also contributes critical infrastructure for next-generation secure communications and computational paradigms.
The fundamental physics explored by SPINNING—with its manipulation of specific vacancy defects and nuclear spins within diamond—also enriches understanding of spin coherence mechanisms and decoherence suppression strategies. These insights can guide future optimization of materials and novel quantum devices with tailored characteristics. Furthermore, the successful demonstration of germanium and tin vacancy center applications within supporting photonic components expands the family of viable solid-state qubits, broadening the scope of materials science research in quantum information.
In summary, the SPINNING project represents a landmark achievement in the quantum computing field, illustrating that spin-photon hybrid quantum systems in diamond offer a powerful, scalable, and energy-efficient alternative to existing superconducting technologies. By combining long coherence times, low error rates, and scalable photonic connectivity, this new approach paves the way for advanced quantum computing platforms. As the quantum technology race intensifies globally, innovations like SPINNING will play a critical role in shaping the future landscape of quantum information science and technology.
Subject of Research: Spin-photon hybrid quantum computing; diamond spin qubits; quantum entanglement; solid-state quantum processors; photonic microresonators.
Article Title: SPINNING: Pioneering Scalable Spin-Photon Quantum Computing with Diamond Qubits
News Publication Date: June 2023
Web References: https://www.spinning-quantencomputing.de/en/partners.html
Image Credits: Fraunhofer IAF
Keywords: Quantum computing, spin qubits, diamond color centers, photonic coupling, quantum entanglement, solid-state quantum technology, coherence time, quantum error rates, distributed quantum computing, quantum hardware, hybrid quantum systems, microresonators
