QuantumConvolutional Codes Derived from GeneralizedReed-Solomon Codes
Salah A. Aly, Andreas Klappenecker, Pradeep KiranSarvepalli
Abstract
Convolutional stabilizer codespromise tomake quantumcommunication morereliable withattractive online encoding anddecoding algorithms. Thispaperintroduces anew approach toconvolutional stabilizer codesbasedondirect limit constructions. A quantumSingleton boundforpureconvolutional stabilizer codesisgiven. A familiy ofquantumconvolutional codesisderived fromgeneralized Reed-Solomon codes. These codesareshowntobeoptimal withrespect tothe(quantum) Singleton bound. I.INTRODUCTION A keyobstacle tothecommunication ofquantuminfor- mationisdecoherence, thespontaneous interaction ofthe environment withtheinformation-carrying quantumsystem. Theprotection ofquantuminformation withquantumerror- correcting codestoreduce orperhaps nearly eliminate the impact ofdecoherence hasledtoahighly developed theory of quantum error-correcting block codes. Somewhat surprisingly, quantum convolutional codeshavereceived less attention. Ollivier andTillich developed thestabilizer framework for quantumconvolutional codes, andaddressed encoding and decoding aspects ofsuchcodes(11), (12). Almediaand Palazzo constructed aconcatenated convolutional codeofrate 1/4withmemorym = 3(1). Forney andGuhaconstructed quantum convolutional codes withrate1/3(3). Also, inajoint workwithGrassl, theyderived rate(n- 2)/n convolutional stabilizer codes(2). Grassl andRotteler constructed quantum convolutional codesfromproduct codes(6), andtheygavea general algorithm toobtain non-catastrophic encoders (5). Inthis paper, wegiveanewapproach toquantum convo- lutional codes based onadirect limit construction, generalize someofthepreviously knownresults. We proveaSingleton boundforpureconvolutional stabilizer codes. We construct afamily ofquantumconvolutional codesbasedonclassical generalized Reed-Solomon codes. Thequantum convolutional codesderived fromthegeneralized Reed-Solomon codesare showntobeoptimal. ~~~~~~q 0< i<p.We canassociate tothegenerator matrix G(D)its semi-infinite coefficient matrix