A Cryo-CMOS Parametric Frequency Divider With-189.1 dBm/Hz Output Noise Floor at 4.2 K for High-Fidelity All-Parametric Quantum Reflectometer

Main-stream quantum computers employ disper-sive reflectometry for quantum-bit (Qubit) state discrimination. An all-parametric quantum reflectometer (APQR) scheme has been proposed for high-fidelity, scalable Qubit array read-out in this letter. For the RF excitation of APQR, a 10.7-16.9 GHz 65-nm cryogenic CMOS (Cryo-CMOS) paramet-ric frequency divider (PFD) is demonstrated here. It adopts a pair of parallelly connected nonlinear artificial transmission lines (NLATLs), a wideband varactor-based dynamic coupler, and a transformer-based CM filter (TCMF). Due to the min-imized device self-heating without dc power consumption and the intrinsic common-mode (CM) to differential-mode (DM) isolation, the PFD presents a measured output thermal noise floor of -189.1 dBm/Hz at 4.2 K. This is only 3.3 dB higher than 4.2-K blackbody radiation. At 4.2 K, the PFD also exhibits an ultralow phase noise of -128.8 dBc/Hz at 1 MHz at 6.75 GHz, which is 2.6 dB lower than a conventional Cryo-CMOS CML divider. It presents a 44.9% relative bandwidth at 4.2 K, which is 2x of the prior art at 300 K.