Add `quick.optimizer` module for optimizers

[ACE07-Sev]

quick.optimizer module for optimizers

Description

Add a module for defining optimizers like gradient-based optimizers. This will require moving the current quick.optimizer which is reserved for circuit optimization (reducing circuit depth) to within the quick.circuit module preferably.

The module will provide a set of optimization algorithms which will later be used to variationally train a circuit. I aim to use this module to create a new strain of synthesis for approximate encoding of states and operators (where the cost is the infidelity between a target state/operator and the state/operator the circuit represents). This module will be required for that.

Tips

• Define the types of optimizers, and how they will interface before adding alot of optimizers.
• Start with a simple optimizer like gradient-descent.

[ACE07-Sev]

I prefer this to be done in 0.0.0, but it may be pushed to 0.1.0 depending on the workload.

[ACE07-Sev]

This has been pushed to a future addition. Instead, I have added the interface for making ansatzes, and users can define arbitrary optimization protocols for training the ansatz however they like. Unless/until I find a specific optimization protocol that deserves its own code inside the package, I will close this issue.

#48