Avoiding Bad Qubits

• 

  David J  (Report)

  January 08, 2020 18:37

  Hello,

  1) The bad qubits will not show up in the graph returned from the sampler.

  You can see this by calling the following code:

  sampler = DWaveSampler()
  sampler.nodelist # This call lists out all of the available qubits.

  You could then take check the difference between this list and a theoretical full list:

  set(range(16*16*8)) - set(sampler.nodelist)
  {577, 1730, 1858, 336, 1105, 1776, 691, 1012, 215, 1276}

  2) If you use minorminer.find_embedding, all of these qubits will be avoided automatically!
  
  

  3) The Ocean tools will not let you specify a bad qubit. You will get an error saying that the graph you submitted is not compatible with the sampler's graph:

  sampler.sample_ising({577:1},{})
  Traceback (most recent call last):
    File "<input>", line 1, in <module>
    File "C:\Users\djohnson\PycharmProjects\dwave\venv\lib\site-packages\dwave\system\samplers\dwave_sampler.py", line 276, in sample_ising
      raise BinaryQuadraticModelStructureError(msg)
  dimod.exceptions.BinaryQuadraticModelStructureError: Problem graph incompatible with solver.

  -1

  Comment actions Permalink
• 

  Thiago T  (Report)

  January 09, 2020 04:21

  David,

  Basically is impossible for an embedding with one bad qubit to run.

  Thank you so much for all the details and examples.

  1

  Comment actions Permalink
• 

  David J  (Report)

  January 15, 2020 23:35

  That's right but it should be possible to avoid this scenario with minorminer's find_embedding.

  0

  Comment actions Permalink

Please sign in to leave a comment.