  A quantum interface between microwave and optical photons is essential for
entangling remote superconducting quantum processors. To preserve fragile
quantum states, a transducer must operate efficiently while generating less
than one photon of noise referred to its input. Here, we present a platform
that meets these criteria, utilizing a combination of electrostatic and
optomechanical interactions in devices made entirely from crystalline silicon.
This platform's small mechanical dissipation and low optical absorption enable
ground-state radiative cooling, resulting in quantum-enabled operation with a
continuous laser drive. Under the optimal settings for high efficiency (low
noise), we measure an external efficiency of $2.2\%$ ($0.47\%$) and an
input-referred added noise of $0.94$ ($0.58$) in microwave-to-optics
conversion. We quantify the transducer throughput using the
efficiency-bandwidth product, finding it exceeds previous demonstrations with
similar noise performance by approximately two orders of magnitude, thereby
paving a practical path to interconnecting remote superconducting qubits.
