A Cryogenic Front-End Module Applied to Readout Two-Qubits with FDM Technology in Superconducting Quantum Computing System

A massive quantum bits (qubits) array is required to mitigate gate error rates in order to realize a practical quantum computing system. An integrated broadband front-end module is employed for the readout of two transmon qubits using frequency division multiplexing (FDM) technology. The frontend module features a customized IQ up-conversion mixer, fabricated using a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$28-\text{nm}$</tex> CMOS process, supporting an RF range of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$4-10 \text{GHz}$</tex> with a conversion gain of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.3 \pm 3 ~\text{dB}$</tex> at 4 K. It achieves sufficient linearity with third-order intermodulation distortion (IM3) exceeding 45 dB and exhibits image rejection ratio (IRR) and LO rejection ratio (LORR) of 57 dB and 50 dB, respectively. The functionality of the front-end module is validated through the successful readout of two qubits. A readout fidelity of around 80 % is measured, consistent with the baseline result.