Southwest Quantum Information and Technology

Error-correcting entanglement swapping using a practical logical photon encoding

Presenting Author: Paul Hilaire, Virginia Tech
Contributing Author(s): Edwin Barnes, Sophia Economou, Frédéric Grosshans

Using linear optics, a two-photon Bell state measurement (BSM) only succeeds with a probability of at best 50%. This limits the performances of many quantum repeater (QR) protocols that use these photonic BSMs either for quantum teleportation or for entanglement swapping. QRs also require loss-tolerance to transfer information at a higher rate than direct fiber transmission and error-correction. A loss-tolerant and error-corrected BSM would therefore enable efficient all-photonic QR schemes. By using either ancillary photonic qubits or nonlinear interaction with atoms, it is possible to overcome the 50% limit but these solutions are neither loss-tolerant nor fault-tolerant. To achieve so, we need to logically encode the photonic qubits and thus to perform a logical BSM. Here, we propose to use a photonic tree graph state which is a logical encoding that can be efficiently produced with a few matter qubits. We develop two logical BSM schemes, denoted "static" and "dynamic", that are both loss-tolerant and error-corrected. In the static protocol, each photonic qubit of a tree graph state is measured with its corresponding qubit of the second tree via standard two-photon BSM which can be implemented with static linear optics. The dynamic protocol requires feedforward and yields better performances. These results can be directly applied to an all-photonic QR protocol that is fault-tolerant, a feature that was lacking in the original proposal

Read this article online: https://arxiv.org/abs/2101.11082, https://quantum-journal.org/papers/q-2021-02-15-397/

(Session 5 : Thursday from 12:00pm-2:00 pm)