  Photonic addressing of superconducting circuits has been proposed to overcome
wiring complexity and heat load challenges, but superconducting-photonic links
suffer from an efficiency-noise trade-off that limits scalability. This
trade-off arises because increasing power conversion efficiency requires
reducing optical power, which makes the converted signal susceptible to shot
noise. We analyze this trade-off and find the infidelity of qubit gates driven
by photonic signals scales inversely with the number of photons used, and
therefore the power efficiency of the converter. While methods like nonlinear
detection or squeezed light could mitigate this effect, we consider generating
higher frequency electrical signals, such as millimeter-waves (100 GHz), using
laser light. At these higher frequencies, circuits have higher operating
temperatures and cooling power budgets. We demonstrate an optically-driven
cryogenic millimeter-wave source with a power efficiency of $10^{-4}$ that can
generate ${1}~\mathrm{\mu W}$ of RF power at 80 GHz with 1500 thermal photons
of added noise at 4 K. Using this source, we perform frequency-domain
spectroscopy of superconducting NbTiN resonators at 80-90 GHz. Our results show
a promising approach to alleviate the efficiency-noise constraints on
optically-driven superconducting circuits while leveraging the benefits of
photonic signal delivery. Further optimization of power efficiency and noise at
high frequencies could make photonic control of superconducting qubits viable
at temperatures exceeding 1 kelvin.
