Wavefunction positivization via automatic differentiation

Understand

We introduce a procedure to systematically search for a local unitary transformation that maps a wavefunction with a non-trivial sign structure into a positive-real form.

• The transformation is parametrized as a quantum circuit compiled into a set of one and two qubit gates.
• We design a cost function that maximizes the average sign of the output state and removes its complex phases.
• The optimization of the gates is performed through automatic differentiation algorithms, widely used in the machine learning community.