Quantum routing of single optical photons with a superconducting flux qubit

TL;DR

This paper proposes a cavity-less hybrid quantum interface that uses a flux qubit to coherently control and route single optical photons, enabling entanglement and quantum state transfer between microwave and optical regimes.

Contribution

It introduces a novel cavity-free scheme for quantum routing and entanglement of single photons using a superconducting flux qubit, simplifying quantum network architectures.

Findings

Demonstrates coherent routing of single photons without optical cavities

Creates hybrid state-path entanglement between photons and qubits

Enables heralded quantum state transfer via measurement

Abstract

Controlling and swapping quantum information in a quantum coherent way between the microwave and optical regimes is essential for building long-range superconducting quantum networks but extremely challenging. We propose a hybrid quantum interface between the microwave and optical domains where the propagation of a single-photon pulse along a nanowaveguide is controlled in a coherent way by tuning electromagnetically induced transparency window with the quantum state of a flux qubit. The qubit can route a single-photon pulse with a single spin in nanodiamond into a quantum superposition of paths without the aid of an optical cavity - simplifying the setup. By preparing the flux qubit in a superposition state our cavity-less scheme creates a hybrid state-path entanglement between a flying single optical photon and a static superconducting qubit, and can conduct heralded quantum state transfer via measurement.