WIP Backend example

[jaygambetta]

WIP Fix the coupling map to be a dictionary just before it goes to the mapper. The code is broken from #363.

Description

Changed the openquantumcompiler to convert to the dictionary to a list just before it is passed to the mapper. In the future the mapper will

Motivation and Context

Because we broke it in last pr

How Has This Been Tested?

running scripts will discuss below twst

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[jaygambetta]

@diego-plan9 I am worried about a few things before we accept this.

Essentially as we move from the dictionary coupling_map to the list coupling_map we have some issues

• In the Backend PR Resolves #262: add qiskit.backend methods... #363 we made the coupling_map change to this as this is what the json schema will look at and what is returned by the API.

coupling_map = [[0,2],[2,1],[2,3]]

• Mapper (not going to change in 0.5 and it still supports the dictionary)

coupling_map = {0: [2], 2: [1,3]}

So the fix i just did is try to do the convert very close to the mapper -- in the openquantumcompiler
however some users will input both so i need to think about how we want to do that. Need to run home now but i will work on this later. However, this is going to break the tests as the user put in some times the old coupling_map. I am going to do a deprecated warning and an if to check or something.

[jaygambetta]

Its passing the test locally.

To do

• Add a test to test against this bug in the future
• Add a python example using the new backends

[diego-plan9]

Thanks @jaygambetta for the quick and lean fix, and @ajavadia for picking up the missing coupling map! As discussed, I tweaked the tests and the docstrings, added an individual test to make sure we can still ensure that the functionality is working during the deprecation, and merging!