A Cryo-CMOS Low-Power Semi-Autonomous Transmon Qubit State Controller in 14-nm FinFET Technology

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A scalable, non-multiplexed cryogenic 14-nm FinFET quantum bit (qubit) state controller (QSC) for use in the semi-autonomous control of superconducting transmon qubits is reported. The QSC includes an augmented general-purpose digital processor that supports waveform generation and phase rotation operations combined with a low-power current-mode single sideband upconversion ${I}/{Q}$ mixer-based RF arbitrary waveform generator (AWG). Implemented in the 14-nm CMOS FinFET technology, the QSC generates control signals in its target 4.5-5.5-GHz-frequency range, achieving an spurious free dynamic range (SFDR) > 50 dB for a signal bandwidth of 500 MHz. With the controller operating in the 4 K stage of a cryostat and connected to a transmon qubit in the cryostat's millikelvin stage, measured transmon $T_{1}$ and $T_{2}$ coherence times were 75.7 and 73 $\mu \text{s}$ , respectively, in each case comparable to results achieved using conventional room temperature (RT) controls. In further tests with transmons, a qubit-limited error rate of 7.76 × 10-4 per Clifford gate is achieved, again comparable to the results achieved using RT controls. The QSC's maximum RF output power is -18 dBm, and power dissipation per qubit under active control is 23 mW.