Microsecond Cryo-CMOS Qubit Readout Design with 10x Power Reduction

CEA-Leti, in collaboration with quantum chip developer Quobly in France, has achieved a significant milestone in quantum technology by creating a chip capable of simultaneous microsecond readouts of multiple quantum qubit devices. This breakthrough has resulted in a remarkable 10x reduction in readout power consumption and a halving of the chip's footprint.

Utilizing FD-SOI CMOS technology, the chip is designed to work seamlessly with Quobly's qubits, which are also constructed using the same technology and operate at cryogenic temperatures. The innovative readout architecture, incorporating 4 and 16 quadrature amplitude modulation (QAM), offers a pathway to developing low-power and scalable quantum integrated circuits with an impressive power consumption of 18.5μW per qubit.

The groundbreaking technology was recently unveiled at the ISSCC 2025 conference held in California, showcasing the potential for revolutionizing quantum computing capabilities.

A key component of the chip is the capacitive-feedback transimpedance amplifier, which efficiently converts the current from the quantum devices into an output voltage. By adjusting the gain through the ratio of capacitance values in its feedback loop, and employing a multiplexing strategy, power consumption is further reduced by enabling a single amplifier to measure multiple qubits.

This advancement sets the stage for the future development of reading thousands of silicon qubits with minimal wiring requirements and without the need for bulky inductors. Overcoming the challenge of the wiring bottleneck is crucial for building large fault-tolerant quantum computers with potentially millions of qubits.

Quobly, with a dedicated team of over 70 experts, has partnered with STMicroelectronics to explore the possibilities of spin qubits on FD-SOI semiconductor processes, further expanding the horizons of quantum computing technology.

• Quobly shows spin qubits on FD-SOI

Lead author of the paper, Quentin Schmidt, emphasized the potential of silicon qubits for enabling large-scale, fault-tolerant quantum computing, citing their compact size, higher operating temperature, and potential compatibility with industrial CMOS processes. Schmidt highlighted the critical need for simultaneous microsecond readouts of numerous devices, a challenge that demands both low power consumption and compact design solutions.

Research director Franck Badets noted the pioneering use of quadrature amplitude modulation (QAM) for simultaneous qubit readouts, showcasing significant improvements in power efficiency and footprint per qubit compared to existing technologies. This breakthrough opens up exciting possibilities for scaling up qubit arrays to unprecedented levels.

Chief scientist at Quobly, Tristan Meunier, expressed the company's commitment to fabricating large-scale quantum computers based on silicon, with the recent progress in scalable qubit readout marking a significant step forward in their roadmap. Leveraging established FD-SOI technology and industry expertise, the collaboration between Quobly and STMicroelectronics aims to produce commercial quantum processor units (QPUs) at scale, building on the groundbreaking work achieved with CEA-Leti.

CEA's various departments have played a crucial role in supporting the development efforts. CEA-List offers guidance on compatibility with future quantum software stacks, while CEA-IRIG provides a unique cryogenic experimental platform, underscoring the collaborative nature of advancements in quantum technology.