Add get_statevector support

[dakk]

Summary

• Add get_statevector capability for shots=0 simulations on BraketLocalBackend (add get_statevector support for BraketLocalBackend #47)
• Add unit test for get_statevector

from qiskit import QuantumCircuit
from qiskit_braket_provider import BraketLocalBackend

backend = BraketLocalBackend(name="default")

q_c = QuantumCircuit(2)
q_c.x(0)
q_c.cx(0, 1)

r = backend.run(q_c, shots=0).result()
print (r.get_statevector())

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[kshitijc]

Thank you for this change @dakk! Looks great! 🙌 Could you please:

• Fix the failing lint check
• Add an example here along with documentation detailing this use case

[dakk]

Thank you for this change @dakk! Looks great! raised_hands Could you please:

* Fix the failing lint check

* Add an example [here](https://github.com/qiskit-community/qiskit-braket-provider/tree/main/docs/how_tos) along with documentation detailing this use case

Lint fixed and add a simple notebook for local simulations and statevector calculation. Let me know if it is ok

[IceKhan13]

@dakk there is still one linter error. Check details on CI.

Basically in braket backend class circuits which has type List[Circuit] and you trying to assign type map to it :)
Make sure types are matched and we are good to do :)

[dakk]

@dakk there is still one linter error. Check details on CI.

Basically in braket backend class circuits which has type List[Circuit] and you trying to assign type map to it :) Make sure types are matched and we are good to do :)

Sorry for that, now should be fixed; I surrounded map with list, so List as type is correct. I've some troubles with running mypy on my computer

[kshitijc]

Would it make sense to merge with this how-to, since the primary motivation is to show how to retrieve a specific result (state vector) here?

[dakk]

I'm not sure about that; the pull add statevector to LocalBackend only, while 2_how_to_retrieve_results_from_backend.ipynb uses AWSBraketProvider backends. LocalBackend is never used in the HOW-TOs, so I thought a new notebook would be a fair solution. Let me know if these arguments makes sense also for you, otherwise I can integrate the code in the existing notebook

[kshitijc]

Nice work @dakk! 🚀