Gate-Error Modelling of Microwave-over-Fiber Drive Links for Superconducting Qubits Under Cryogenic Heat Constraints
DOI:
https://doi.org/10.58564/IJCCN.2.3.2026.23Keywords:
Microwave photonics, Analog optical link, Superconducting qubit, Shot noise, Cryogenic heat loadAbstract
Analog microwave-over-fiber (MoF) links can deliver qubit-control signals to a cryogenic photodiode with a much lower passive heat load than coaxial wiring. However, the required photocurrent dissipates heat at the cold stage, and its shot noise perturbs the qubit. This paper develops a physics-structured model that maps the Mach–Zehnder modulator (MZM) bias, the modulation depth, the photocurrent scale, and the gate duration of an analog MoF link to the link-induced average infidelity of a transmon gate. The model is then used to design links that minimize idle optical heat. The optical link was simulated in OptiSystem software, and the received photocurrents drove a three-level transmon model with Lindblad decoherence in MATLAB. Across 1344 simulation runs covering 15–45 dB of optical attenuation, bias angles of 90°–170°, modulation indices of 0.2–1.3, and gate durations of 20 and 40 ns, deterministic link distortion contributed an infidelity of at most , the link-induced error scaled as , and leakage accounted for about 60% of it. The closed-form model, which includes pulse-induced shot noise and Bessel-function drive compression and has a single calibrated coefficient, predicted held-out low-power and low-bias configurations with a logarithmic root-mean-square error of 0.040 decades, compared with 0.155–0.412 decades for three reference models. Six operating points designed with the frozen model met their pre-registered error targets to within 8.5% in new simulations and required 9.1–11.1 times less idle optical power at the photodiode than the best quadrature-biased design.
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