The Correcting Capacities of Linear Codes

Diego Ruano

Thomas Alfred Walker, Samuel L. Braunstein

In this article we outline a method for generating linear optics circuits that encode quantum-error-correcting codes. Using this method we produce a single-error-correcting code encoding one wave packet over five which can be implemented using linear optics and feed-forward correction. This code improves on the capacity of the best known code that can be implemented using linear optics and saturates the lower bound for the number of carriers needed for a single-error-correcting code. Our code can correct arbitrary single errors that occur randomly on each wave packet corresponding to a non-Gaussian error model, thus circumventing the so-called no-go theorem for Gaussian quantum-error correction.

James L. Massey

Todd A. Brun, Igor Devetak, Min-Hsiu Hsieh

We show how entanglement shared between encoder and decoder can simplify the theory of quantum error correction. The entanglement-assisted quantum codes we describe do not require the dual-containing constraint necessary for standard quantum error-correcting codes, thus allowing us to "quantize" all of classical linear coding theory. In particular, efficient modern classical codes that attain the Shannon capacity can be made into entanglement-assisted quantum codes attaining the hashing bound (closely related to the quantum capacity). For systems without large amounts of shared entanglement, these codes can also be used as catalytic codes, in which a small amount of initial entanglement enables quantum communication.

Martin Bossert, F. Hergert

Santhosh Kumar, Robert Calderbank, Henry D. Pfister

The quantum erasure channel is the simplest example of a quantum communication channel and its information capacity is known precisely. The subclass of quantum error-correcting codes called stabilizer codes is known to contain capacity-achieving sequences for the quantum erasure channel, but no efficient method is known to construct these sequences. In this article, we explicitly describe a capacity-achieving code sequence for the quantum erasure channel. In particular, we show that Calderbank-Shor-Steane (CSS) stabilizer codes constructed from self-orthogonal binary linear codes are capacity-achieving on the quantum erasure channel if the binary linear codes are capacity-achieving on the binary erasure channel. Recently, Reed-Muller codes were shown to achieve capacity on classical erasure channels. Using this, we show that CSS codes constructed from binary Reed-Muller codes achieve the capacity of the quantum erasure channel. The capacity-achieving nature of these CSS codes is also explained from a GF(4) perspective.