  In this paper, we provide a system level perspective on the design of control
electronics for large scale quantum systems. Quantum computing systems with
high-fidelity control and readout, coherent coupling, calibrated gates, and
reconfigurable circuits with low error rates are expected to have superior
quantum volumes. Cryogenic CMOS plays a crucial role in the realization of
scalable quantum computers, by minimizing the feature size, lowering the cost,
power consumption, and implementing low latency error correction. Our approach
toward achieving scalable feed-back based control systems includes the design
of memory based arbitrary waveform generators (AWG's), wide band radio
frequency analog to digital converters, integrated amplifier chain, and state
discriminators that can be synchronized with gate sequences. Digitally assisted
designs, when implemented in an advanced CMOS node such as 7 nm can reap the
benefits of low power due to scaling. A qubit readout chain demands several
amplification stages before the digitizer. We propose the co-integration of our
in-house developed InP HEMT LNAs with CMOS LNA stages to achieve the required
gain at the digitizer input with minimal area. Our approach using high
impedance matching between the HEMT LNA and the cryogenic CMOS receiver can
relax the design constraints of an inverter-based CMOS LNA, paving the way
toward a fully integrated qubit readout chain. The qubit state discriminator
consists of a digital signal processor that computes the qubit state from the
digitizer output and a pre-determined threshold. The proposed system realizes
feedback-based optimal control for error mitigation and reduction of the
required data rate through the serial interface to room temperature
electronics.
