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belief-propagation

Progress

  • Mar 30
    • change input method
    • change parallel thread from shell to c++
  • Apr 1
    • get run result and save
  • Apr 4
    • plot result.
    • plotted counts for errors with weight 0, 1, 2 respectively. Those counts are smaller than the converged error. Because in large-weight errors, there will be single error as well. Hence these counts are not meaningful. For a meaningful comparison, one should plot the weight of the errors, instead of counts. This comparison has been done before, hence not shown here. For reference see "Weilei Research Note.pdf"
    • check iteration, see improvement about 20-30% in converge rate. no threshold.
  • Apr 5
    • replace bp decoding using syndrome based and LLR simplied. Passing test with 7 qubit code
  • Apr 6
    • test repetition code
    • test toric code and check result.
    • compare with itpp LDPC_Code.bp_decode(). Most result are the same, but in toric code, error=[1 1 0 0 ... 0] get a different result, but error=[0 ... 0 1 1 0 ... 0] get the saem result. Not sure why and not sure if this produce a statistical different in lasrge number of tests
    • run full simulation on toric codes and compare. Itpp perform much better. It can even decode many double errors. The difference I oberserved in algorithm is that (a) itpp use intergers, which I thing only save some time to make it faster than float calculation. (b) BoxPlus. This might be an optimization, see ref
  • Apr 7
    • itpp result: no improvement using integer in convergence, but the program is at least 10 times faster. When using min sum (Dint2 =0), it get improvements and get faster again.
    • writing my own function. min sum, normalization. offset.
    • my min sun is slightly worse than Dint2=0
    • iteration 10 show similar big improvement percentage. Still relatively lower than corresponding itpp
    • write decoder as a class in head file, instead of functions
    • layered schedule itself show no improvement. But layered scheduling plus enhanced feedback show improvement with a factor greater than 10. Run it overnight to see if there is a threshold. Yehua's paper has threshold around 7%. Hence I am looking for the range around 1%

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Using belief propagation to decode quantum codes

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