[News] Chinese Research Team Develops Ultra-Low Temperature Quantum Interface Reference Chip

Recently, the research team led by Professor Cheng Lin from the School of Microelectronics at the University of Science and Technology of China (USTC), in collaboration with Professor Luo Wenji’s team from the University of Macau, has made significant progress in the study of ultra-low temperature quantum interface reference circuits. This research is the first to propose an ultra-low temperature, low-power CMOS voltage reference that does not require trimming and can achieve self-compensation for both temperature and process variations.

With the rapid development of quantum computing technology, quantum processors impose increasingly stringent requirements on qubit quality, scalability, quantum error correction, environmental control, and computational accuracy.

Currently, most quantum computers, such as superconducting quantum computers, need to operate in environments close to absolute zero to minimize thermal noise interference with qubits. Therefore, quantum computers require a large number of high-fidelity qubits and control interface circuits to transmit signals between the classical domain at room temperature and the quantum domain at low temperatures.

Among various interface circuit modules, the reference circuit is crucial. To ensure reliability under different operating conditions such as initial testing, thermal transitions, and system anomalies, the voltage reference must maintain stable output characteristics across the temperature range from the dilution refrigerator to the external environment (from 300K to 4K). This necessitates extremely low sensitivity to temperature fluctuations and process variations.

However, standard CMOS devices exhibit threshold voltage drift, intensified nonlinear effects, and kink effects under ultra-low temperatures, posing significant challenges to the adaptability of quantum interface reference circuits in extreme low-temperature environments.

Therefore, designing a highly robust quantum interface reference circuit suitable for ultra-low temperature environments will help address key technical challenges in the large-scale application of quantum computing.

(Photo credit: University of Science and Technology of China)

(a) The working environment of the quantum interface chip; (b) Comparison of temperature and process precision showing significant advantages over state-of-the-art research.

To this end, the research team designed an ultra-low temperature, low-power CMOS voltage reference quantum interface circuit that does not require trimming and proposed a technology that achieves self-compensation for both temperature and process variations.

This reference circuit delivers high-precision voltage output across a wide temperature range of 300K to 4K and demonstrates exceptional robustness.

(Photo credit: University of Science and Technology of China)

(c) Microscope image of the chip; (d) Temperature curves of 80 untrimmed chips from two batches of testing; (e) Measurement environment using a dilution refrigerator and automatic counting system.

The design adopts a standard CMOS 180 nm process, with a total of 80 chips tested across two batches (as shown in image (c)). The test results, shown in image (d), indicate that with only a single model calibration, cross-batch trimming-free operation can be achieved. The reference circuit has an average temperature coefficient (TC) of 76.9 ppm/K, and the voltage fluctuation is only 0.72%, demonstrating high temperature and process precision.

Operating within the 300K to 4K range, the circuit consumes only 195-304 nW of power, with an average output voltage of 1.045 V. This voltage reference achieves nanowatt-level ultra-low power consumption under a standard CMOS process and exhibits excellent stability against process, voltage, and temperature (PVT) variations. It can be integrated into quantum interface circuits at low cost and applied to ultra-low temperature environments such as space exploration, providing a reliable solution for these extreme conditions.

(Photo credit: University of Science and Technology of China)