Add optimal layout synthesis to Cirq

[tanujkhattar]

Is your feature request related to a use case or problem? Please describe.
Cirq now has abstractions for qubit routing and an implementation of CQCs qubit routing algorithm as described in https://arxiv.org/abs/1902.08091

There is more recent work on using SMT solvers for qubit routing which has a significantly better performance in terms of number of swaps inserted, compared to CQCs heuristic routing algorithm. This work is described in https://arxiv.org/abs/2007.15671 and a corresponding implementation exists in https://github.com/tbcdebug/OLSQ

It would be nice to either add an implementation of the algorithm described in the paper to Cirq; or have a converter to/from Cirq to the OLSQ solver so that cirq users can easily route their cirq circuits using this algorithm.

This would be a good independent project for anyone who is interested in learning more about qubit routing.

What is the urgency from your perspective for this issue? Is it blocking important work?
P3 - I'm not really blocked by it, it is an idea I'd like to discuss / suggestion based on principle

[anonymousr007]

Hello @tanujkhattar, I want to work on this issue as a part-time project. Can you please assign me this issue? We discuss this issue very briefly. Thanks.

[senecameeks]

@tanujkhattar can you assign to me? I think this would be a great learning opportunity :)

[dstrain115]

Cirq cync: accepted but low priority. Seneca will pick another issue, so this is open for volunteers.