Entanglement is the essential resource that enables quantum information and processing tasks. Historically, sources of entangled light were developed as experimental tools to test the foundations of quantum mechanics. In this study, we make an extreme version of such a source, where the entangled photons are separated in energy by 5 orders of magnitude, to engineer a quantum interconnect between light and superconducting microwave devices.
Our entanglement source is an integrated chip-scale device with a specially designed acoustic transducer, whose vibrations can simultaneously modulate the frequency of an optical cavity and generate an oscillating voltage in a superconducting electrical resonator. We operate this transducer at cryogenic temperatures to maintain the acoustic and electrical components of the device close to their quantum ground state and excite it with laser pulses to generate entangled pairs. We measure statistical correlations between the optical and microwave emission to verify entanglement.
Our work demonstrates a fundamental prerequisite for a quantum information processing architecture in which room-temperature optical communication links may be used to network superconducting quantum-bit processors in distant cryogenic setups.
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