Microsecond cryo-CMOS qubit readout design with 10x power reduction
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CEA-Leti and quantum chip developer Quobly in France have developed a chip for simultaneous microsecond readouts of tens of quantum qubit devices, reducing the readout power consumption by 10x and footprint by half.
The chip uses FD-SOI CMOS technology and can be combined with Quobly’s qubits built in the same technology, operating at cryogenic temperatures. This readout architecture with 4 and 16 quadrature amplitude modulation (QAM) provides a path to low power and scalable quantum integrated circuits with a power consumption of 18.5μW/qubit.
The technology was described at the ISSCC 2025 conference in California this week.
A capacitive-feedback transimpedance amplifier converts the current coming from the quantum devices into an output voltage. Its gain can be set by adjusting the ratio of the values of the two capacitances of its feedback loop and the multiplexing strategy reduces power by using one of these amplifiers to measure several qubits.
This paves the way toward developing the readout of thousands of silicon qubits with a limited number of wires and without the need of bulky inductors. This avoid the challenge of the wiring bottleneck in building a large fault-tolerant quantum computer with a million qubits.
Quobly has a team of over 70 people working on this, and has teamed with STMicroelectronics to develop spin qubits on FD-SOI semiconductor processes.
“The silicon qubit is a promising candidate for large-scale, fault-tolerant quantum computing due to its small footprint, higher operating temperature and possible compatibility with industrial CMOS processes,” said Quentin Schmidt, lead author of the paper. “But the need for a simultaneous microsecond readout of thousands of devices is especially challenging in terms of both power consumption and size.”
“This is the first time that as-complex-a-modulation scheme as QAM has been used to address the simultaneous readout of several qubits,” explained Franck Badets, research director of the institute’s Silicon Components Department. “The associated improvements in power efficiency and footprint per qubit for a single amplifier, compared to frequency division multiplexing access state-of-the-art, demonstrated with OOK modulations, open bright perspectives for larger-scale qubit arrays.”
“Quobly’s goal is to fabricate large-scale quantum computers based on silicon. This paper demonstrates key progress toward a scalable readout of the qubits and is a major advance in its roadmap,” said Tristan Meunier, chief scientist at Quobly.
“Our process, which leverages established FD-SOI technology to benefit from the expertise of the semiconductor industry, is already paying off: This work demonstrates the co-integration of classical electronic functions at low temperature to simultaneously read and control multiple qubits on chip with record low consumption and compact design. Quobly’s partnership with STMicroelectronics, to produce commercial quantum processor units (QPUs) at scale, builds on the ground-breaking work done with CEA-Leti.”
Other parts of the CEA also supported the development. CEA-List offers guidance on compatibility with future quantum software stacks, while CEA-IRIG provides a one-of-a-kind cryogenic experimental platform.
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