Quantum science and technology promise the realization of a powerful
computational resource that relies on a network of quantum processors connected
with low loss and low noise communication channels capable of distributing
entangled states [1,2]. While superconducting microwave qubits (3-8 GHz)
operating in cryogenic environments have emerged as promising candidates for
quantum processor nodes due to their strong Josephson nonlinearity and low loss
[3], the information between spatially separated processor nodes will likely be
carried at room temperature via telecommunication photons (200 THz) propagating
in low loss optical fibers. Transduction of quantum information [4-10] between
these disparate frequencies is therefore critical to leverage the advantages of
each platform by interfacing quantum resources. Here, we demonstrate coherent
optical control of a superconducting qubit. We achieve this by developing a
microwave-optical quantum transducer that operates with up to 1.18% conversion
efficiency (1.16% cooperativity) and demonstrate optically-driven Rabi
oscillations (2.27 MHz) in a superconducting qubit without impacting qubit
coherence times (800 ns). Finally, we discuss outlooks towards using the
transducer to network quantum processor nodes