Direct quantum error detection in multiplexed photonic transmission channels

Abstract

The detection of quantum errors is of particular importance to the development of reliable engineered quantum systems. Whereas previous error-detection schemes were mostly developed for πphase-flip associated with solid-state qubits, here we introduce a protocol for direct detection of arbitrary continuous phase errors in the transmission of multiphoton spatially entangled quantum states. We present a design and experimental evidence for its realization in an integrated photonic circuit using gradually coupled waveguides with specially detuned propagation constants. We anticipate that our approach will facilitate the development of error-robust photonic devices for the processing and communication of quantum information.