Quantum interface between single- and dual-rail optical qubits
David Drahi, Demid Sychev, Khurram K. Pirov, Ekaterina A. Sazhina, Valeriy A. Novikov, Ian A. Walmsley, Alexander I. Lvovsky · arXiv (Cornell University) · 2019
Today's most widely used method of encoding quantum information in optical qubits is the dual-rail basis, often carried out through the polarisation of a single photon. On the other hand, many stationary carriers of quantum information - such as atoms - couple to light via the single-rail encoding in which the qubit is encoded in the number of photons. As such, interconversion between the two encodings is paramount in order to achieve cohesive quantum networks. In this paper, we demonstrate this by generating an entangled resource between the two encodings and using it to teleport a dual-rail qubit onto its single-rail counterpart. Our results yield an average fidelity of $\mathcal{F}= (92.8\pm2.2)\%$ for the teleportation and $\mathcal{F}= (89.7\pm2.1)\%$ for entanglement swapping, thus confirming the applicability of this scheme for a real-world implementation. This work completes the set of tools necessary for the interconversion between the three primary encodings of the qubit in the optical field: single-rail, dual-rail and continuous-variable.