Demonstration of photon encoding interconversion for heterogeneous quantum networking

Photonic quantum network links are required to scale up matter-based quantum systems, including quantum computers, quantum sensors, and more. Heterogeneous quantum networks comprised of these systems, such as trapped-ion and superconducting circuit-based qubits, must achieve entanglement distribution between these different qubit architectures to exploit the strengths of each; namely ion-trapped systems providing an ease of generation of polarization qubits and superconducting qubits generating high fidelity time-bin qubits. One barrier to heterogeneous connectivity is precisely this variety of photonic degrees of freedom in which quantum information is encoded, such as those mentioned above, frequency bin, time-energy, etc. Here, we present experimental results on photon basis interconversion modules in the telecom C-band that convert time-bin qubits to polarization qubits and vice versa. We characterize the performance of these by observing how fidelity of a Bell state changes with respect to changes in photon transmission rate. Our results show that our prototypes can be used within high-fidelity entanglement swapping protocols between heterogeneous quantum memories.