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Public Seminar of PhD Candidate:
Study of Quantum Low Density Parity Check and Quantum Degenerate Codes

Speaker:Mr. K.H. HO
Affiliation:Department of Physics, HKU
Date:December 16, 2008 (Tue)
Time:2:30-3:30 p.m.
Venue:Room 518A (Physics Library), 5/F, Chong Yuet Ming Physics Building, HKU


Entanglement distillation purification (EDP) protocol protects quantum states from interaction with the environment. In 1995, Shor has made the remarkable discovery that quantum information can be protected against quantum errors by means of quantum error-correcting (QECC) codes. Many quantum codes have been discovered and investigated since then. In particular, the so-called quantum low density parity check (QLDPC) codes recently have been extensively studied. In this talk, a numerical performance analysis of an adaptive entanglement distillation scheme using QLDPC codes is studied. The expected yield of this adaptive distillation scheme to combat depolarization errors is found to exceed that of Leung and Shor whenever the error probability is less than about 0.07 or greater than about 0.28. This finding illustrates the effectiveness of using QLDPC codes in entanglement distillation. In particular, it can replace the Leung and Shor as well as the Hosten et al.'s protocols in adaptive entanglement purification.

Along other line, the distillation of entanglement from multi-partite entangled states using degenerate quantum codes is also studied in this talk. This kind of codes are those that do not reveal the compete error syndrome. In particular, a purification scheme for depolarized GHZ states shared among more than two players by means of degenerate quantum codes and one-way classical communications is investigated. This scheme is found to tolerate more noise than all other one-way schemes known to date.