Experimental Studies of Millimeter-Wave CMOS LO Circuits for High-Temperature Qubits Operations

Operating physical quantum bits (qubits) at higher temperatures—and consequently millimeter-wave frequencies—has the potential to relax cooling requirements and enable efficient scaling of qubit numbers. In parallel, Cryo-CMOS control and readout circuits must scale in frequency to allow for tight integration. This letter presents the study of Cryo-CMOS millimeter-wave local oscillators (LOs) generation circuits for this purpose. Implemented in TSMC 40-nm CMOS technology, we demonstrate successful implementation of a 30-GHz oscillator consuming 0.235 mW from a 0.5-V supply, as well as two 30-GHz divide-by-80 LO chains using latch-based and injection-locked frequency dividers (ILFDs), all operating at 4 K. Testing setups and techniques are described.