Superconducting qubits are unable to support interactivity beyond that occurring locally, with nearby and neighboring (co-located) qubits. By inserting microwave waveguides to function as the basis for quantum interconnects, quantum information can travel from one location to another. The microwave transmission line, or waveguide, drives that communication, as the excitations contained within the qubits generate photon pairs that emit into the waveguide and then travel to two distant processing nodes. The photons are entangled, acting as a singular system, and distributing entanglement throughout a quantum network at a highly efficient rate.
The new waveguide quantum electrodynamics architecture that generated the photons showed that qubits can function as quantum emitters for the waveguide. The researchers further demonstrated that quantum interference between the photons emitted into the waveguide generated entangled, itinerant photons that traveled in opposite directions. Those photons and their motion can be used for long-distance communication between quantum processors.
In performing computations, classical computers rely on wires to route information back and forth through a processor. In a quantum computer, information itself is quantum mechanical, as well as extremely fragile, leading to the need for strategies that simultaneously process and communicate information.
Where spontaneous parametric down-conversion and photodetectors can generate entangled photons in an optical system, that entanglement is generally random. That randomness detracts from modularity and the entanglement’s ability to support the on-demand communication of quantum information within a distributed system.
The researchers have yet to perform the communication between processors, showing instead how generated photons are both useful in application for quantum communication and in interconnection protocols.
The work was published in Science Advances (www.doi:10.1126/sciadv.abb8780).
