Abstract
Linking classical microwave electrical circuits to the optical telecommunication band is at the core of modern communication. Future quantum information networks will require coherent microwave-to-optical conversion to link electronic quantum processors and memories via low-loss optical telecommunication networks. Efficient conversion can be achieved with electro-optical modulators operating at the single microwave photon level. In the standard electro-optic modulation scheme this is impossible because both, up- and downconverted, sidebands are necessarily present. Here we demonstrate true single sideband up- or downconversion in a triply resonant whispering gallery mode resonator by explicitly addressing modes with asymmetric free spectral range. Compared to previous experiments, we show a three orders of magnitude improvement of the electro-optical conversion efficiency reaching 0.1% photon number conversion for a 10GHz microwave tone at 0.42mW of optical pump power. The presented scheme is fully compatible with existing superconducting 3D circuit quantum electrodynamics technology and can be used for non-classical state conversion and communication. Our conversion bandwidth is larger than 1MHz and not fundamentally limited.
Highlights
Efficient conversion of signals between the microwave and the optical domain is a key feature required in classical and quantum communication networks
The resulting phase modulation creates sidebands symmetrically around the optical pump frequency, which can be described by sum frequency generation (SFG) and difference frequency generation (DFG)
We present a new take on the classical electro-optical modulation within a lithium niobate whispering gallery mode resonator, where single-sideband operation is made possible without detuning
Summary
Efficient conversion of signals between the microwave and the optical domain is a key feature required in classical and quantum communication networks. The best reported photon conversion efficiency so far was of the order of 0.0001% per mW optical pump power [21,22] These implementations could not individually address either SFG or DFG, and always include additional noise from the spontaneous process. Since the mode crossings are temperature dependent, they can be used to tune the microwave input frequency over several tens of MHz and to switch between SFG and DFG With this system, we reach a photon number conversion efficiency of 0.2% per milliwatt optical pump power, which is 3 orders of magnitude larger than in previous works [21,22]. We already reach a bandwidth of 1 MHz
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