`AbstractOperator` operations necessary for Lindblad Master Equation

Created by: PhilipVinc

When working with the lindblad master equation the user typically specifies an hamiltonian and a set of loss operators L_i, which are in general non-hermitian. L_i and usually local, though it might be interesting to see what happens with nonlocal dissipation (even if there is not much literature on the subject, e.g. a system that dissipates only from the k=0 mode).

What we need is a way to construct, given an AbstractOperator L_i, the AbstractOperator L_i^\dagger L_i. Therefore we need to support the following three operations:

• Transpose
• Conjugation
• Product

Defining those as virtual methods on the abstract base class would require that all AbstractOperators, even those not really relevant to Loss Operators, support this operation.

To keep things simple, I propose we start by only supporting LocalOperators as loss operators, and implement those 3 operations there. In the future we might relax this constraint.

@gcarleo What do you think?