Quantum computing has long been heralded as the next transformative leap in computational technology, promising to solve complex problems far beyond the reach of classical machines. Yet, a fundamental barrier lies in the difficulty of scaling quantum systems to the millions of quantum bits, or qubits, necessary for practical and commercially viable quantum computers. In a groundbreaking development from researchers at the University of Sydney, led by Professor David Reilly, a significant stride has been made toward overcoming this challenge with the creation of a cryogenic control platform. This system integrates control electronics directly onto a silicon chip capable of operating near absolute zero temperatures, potentially revolutionizing the architecture of quantum processors.
Until now, one of the biggest roadblocks in quantum computing has been managing the interface between qubits and the classical electronics needed to control them. Traditional approaches employ wiring that connects room-temperature electronics to qubits maintained at sub-kelvin temperatures. This setup is increasingly impractical as the number of qubits rises, creating prohibitive heat loads, electrical noise, and latency issues. By engineering control electronics that operate in the millikelvin environment where the qubits reside, Professor Reilly’s team has successfully demonstrated a scalable path forward, ensuring that qubit fidelity and coherence are not compromised by proximity to control systems.
Central to this achievement is the use of spin qubits encoded in silicon, which offer inherent advantages due to their compatibility with standard complementary metal-oxide-semiconductor (CMOS) fabrication techniques. Unlike other qubit types, spin qubits hold promise for seamless integration with existing semiconductor manufacturing infrastructure, supporting possibilities for mass production. The control chip designed by the Sydney group employs these CMOS-compatible elements, enabling precise manipulation of electron spin states at temperatures just a fraction above absolute zero (-273.15°C). This marriage of mature semiconductor technology with delicate quantum systems is a pivotal advance.
Integrating control circuitry within the cryogenic environment entails formidable technical demands. Electronics must dissipate only minuscule amounts of power to avoid heating the qubits beyond their operational thresholds. The chip developed by the researchers consumes less than 10 microwatts, most of which powers digital logic, while analog components are optimized to dissipate merely nanowatts per megahertz. This ultra-low power consumption is critical, as any thermal disturbance risks decoherence of the fragile quantum states. The achievement reflects more than a decade of incremental design refinement to master low-noise, cryogenic operation of complex electronics.
Beyond power efficiency, the team tackled issues of electrical noise and interference, potential killers of qubit stability. The cryo-CMOS chip’s careful layout and shielding allow it to switch transistors in close proximity—less than a millimeter—from the qubits without measurable detriment to their coherence time or gate fidelity. Rigorous experimental benchmarking compared the chip’s performance against traditional room-temperature control systems connected via cables, finding negligible degradation in one- and two-qubit gate operations. This validates the feasibility of tightly integrated control-electronic architectures.
Industry cooperation played a vital role in realizing this milestone. The qubits themselves were furnished by Diraq, a spin-out from the University of New South Wales, under the leadership of Professor Andrew Dzurak. Meanwhile, the silicon-based control chip is being commercialized by Emergence Quantum, a company co-founded by Professor Reilly and Dr. Thomas Ohki that emerged explicitly to translate these laboratory advances into deployable technology. Such synergy between academic research and commercial ventures accelerates the journey from proof-of-concept demos to robust quantum hardware platforms.
At the heart of the scientific accomplishment lies a series of complex experiments meticulously conducted by PhD researcher and lead author Dr. Sam Bartee. These experiments characterized quantum gate operations controlled by the milli-kelvin CMOS chiplet, confirming resilience of quantum coherence and gate fidelity in an environment previously deemed too hostile for integrated electronics. Dr. Bartee’s work exemplifies the emerging generation of quantum engineers propelling the field into new frontiers of scale and practicality.
The implications of this cryogenic control platform extend well beyond computing. As Professor Reilly emphasizes, the capacity to integrate sophisticated electronics at ultra-low temperatures can revolutionize quantum sensors, which demand similar environmental conditions to exploit quantum-enhanced sensitivity. Moreover, data centers of the future, grappling with escalating energy consumption, might benefit from quantum devices designed with tightly coupled cryogenic control electronics, yielding systems that compute more efficiently and with greater precision.
Complementing the technical ingenuity is an astute commercial vision. Professor Dzurak, CEO of Diraq, highlights how integrating silicon qubits with classical control electronics in compact packages aims to make quantum computers more affordable and energy-efficient. This evolution could democratize access to quantum computational power, accelerating innovation in fields from cryptography to materials science. The advances bring us closer to realizing the long-envisioned potential of quantum technologies impacting everyday life.
Technically, the design challenges were immense, encompassing noise mitigation, thermal budget restrictions, and precise gate implementation. The cryo-CMOS chip’s architecture balances digital and analog domains, enabling precise pulse-shaping and qubit control sequences. Notably, the analog part dissipates an exceptionally low power which allows the system’s scalability up to millions of qubits without a corresponding jump in cooling requirements. This shifts the paradigm from bulky and unwieldy quantum systems toward compact, integrable quantum processors.
Professor Reilly’s assertion that fragile spin qubits "hardly notice" the presence of switching transistors nearby encapsulates the finesse achieved. This subtlety speaks to the meticulous electrical engineering that shields quantum states from decoherence while maintaining fast, accurate control signals. Such a breakthrough disrupts prior assumptions and validates decades of theoretical modeling about the viability of cryogenic integration.
Furthermore, the tight collaboration between multiple institutions and spin-out companies signifies a maturing ecosystem that can sustain the quantum computing revolution. Combining materials science, electrical engineering, quantum physics, and entrepreneurship, this research serves as a model for future interdisciplinary innovation. The shared expertise, resources, and strategic partnerships substantially reduce the time from discovery to real-world application.
Looking toward the future, this cryogenic control system opens avenues for broader exploration of hybrid quantum-classical architectures. As algorithms become more sophisticated and qubit counts swell, integrated control at operating temperatures eases architectural constraints. The work performed at the University of Sydney sets a powerful precedent and offers a foundation for global quantum technology efforts to build upon.
In summary, the “Spin-qubit control with a milli-kelvin CMOS chip” reported in Nature is a defining advancement that transforms our approach to quantum control electronics. By demonstrating ultra-low power, low-interference integrated circuits operating within the qubit cooling environment, Professor David Reilly and his team have paved the way for quantum computers operating at scales previously deemed impossible. Their contribution marks a turning point from experimental curiosity toward scalable quantum computing infrastructure, signaling a new era of technological potential.
Subject of Research: Quantum computing, spin qubits, and cryogenic control electronics integration for scalable quantum processors.
Article Title: Spin-qubit control with a milli-kelvin CMOS chip
News Publication Date: 25 June 2025
Web References:
- https://www.nature.com/
- https://www.sydney.edu.au/science/about/our-people/academic-staff/david-reilly.html
- https://emergencequantum.com/
- https://diraq.com/
References:
Bartee, S. et al. ‘Spin-qubit control with a milli-Kelvin CMOS chip’ (Nature 2025) DOI: 10.1038/s41586-025-09157-x
Image Credits: Fiona Wolf/University of Sydney
Keywords:
Quantum computing, Quantum processors, Electrical engineering, Quantum information, Quantum information processing, Quantum information science
