GlobalFoundries' Cryogenic SiGe LNA Cuts Power to 0.74mW for Scalable Quantum Readout

A team of engineers from GlobalFoundries and research institutions has introduced a sub-milliwatt Ku-band cryogenic low-noise amplifier (LNA) designed for scalable quantum readout systems. The LNA, implemented in GlobalFoundries' 130CBIC SiGe BiCMOS process, consumes only 0.74 mW of DC power while achieving an average noise temperature of approximately 14 K across 12-18 GHz. With a peak gain of 28 dB around 16.5 GHz, this amplifier is intended for integration with a Josephson parametric amplifier (JPA) on the Still stage of a sub-Kelvin qubit readout chain. The paper, accepted at the IEEE BCICTS symposium, claims this is the lowest reported DC power for a Ku-band cryogenic SiGe LNA, addressing the critical need for energy-efficient cryogenic electronics in large-scale quantum processors.

The amplifier employs a four-stage cascode topology with balun-coupled interstage matching, featuring a Q-enhanced resonance tank controlled by 2-bit switches for frequency tuning. A voltage-controlled cross-coupled negative-gm cell (Q-cell) is optimized at each temperature stage to maintain stable, high-performance operation. Characterized at 2.5 K, the LNA demonstrates excellent in-band performance while operating at power levels far below conventional designs. This breakthrough is significant for quantum computing because it drastically reduces thermal load on cryostats, allowing integration of more readout channels for multi-qubit systems without exceeding cooling budgets. The design's scalability and low-power consumption make it a key enabler for practical quantum processors with hundreds or thousands of qubits.