An All Linear Optical Quantum Memory Based on Quantum Error Correction

When photons are sent through a fiber as part of a quantum communication protocol, the error that is most difficult to correct is photon loss. Here, we propose and analyze a two-to-four qubit encoding scheme, which can recover the loss of one qubit in the transmission. This device acts as a repeater when it is placed in series to cover a distance larger than the attenuation length of the fiber, and it acts as an optical quantum memory when it is inserted in a fiber loop. We call this dual-purpose device a ``quantum transponder.''