A Cryogenic 12 GHz Frequency Doubler With Temperature Compensation for Trapped-Ion Quantum Computer

This brief presents a frequency doubler (FD) for a microwave-control system intended for an $^{171}\text {Yb}^{+}$ ion-trap-based quantum computer. The circuit is optimized for frequency multiplication from 11GHz to 13 GHz with a ≥29 dBc fundamental- and third harmonic rejection over the entire frequency range and peak HRR1/HRR3 of 37 dBc/ 39 dBc. This enables the microwave frequency generation to drive the hyperfine transitions in the electronic ground state of an $^{171}\text {Yb}^{+}$ ion at 12.6 GHz. Cryogenic measurements of the FD down to 4.5 K enable circuit functionality verification for the intended low-temperature operation. Additionally, insights into the cryogenic temperature effects of the employed BiCMOS technology are obtained and used to derive a biasing control methodology for constant performance in the temperature range of 300K to 4.5K. The proposed circuit is silicon-proven and fabricated in a $\mathrm {0.13~ \mu \text {m} }$ SiGe BiCMOS process, consuming a core area of only 0.034 mm2.