v.1.9.7

Minor convenience changes
Major Performance improvements for wavefunction simulation (without using expecation values)

• Fix U.export_to("path.png)" syntax
• Deepcopy gates in __iadd__ of QCircuit (#360)
• Simulation performance improvements (#359)
• Only apply keymap if necessary in simulate
• Simplify comparison and only calculate index bitstring when necessary in from_array
• Fix numbering_out parameter in initialize_bitstring and remove MSB2LSB/LSB2MSB keymap in from_array
• Optimize initialize_bitstring
• Update requirements.txt (no scipy version restriction, issue #361)
• rdm calculation more flexible (#363)
• Update version.py

RDM calculations:
calling the rdm function in the quantum chemistry module with evaluate=False gives back a tq.QTensor object
direct evaluation within compute_rdm is however faster (no repetitions in the simulation)

rdm1, rdm2 = mol.compute_rdms(U=U, evaluate=False)

Performance improvements @ohuettenhofer
see the original pr: #359
no syntax changes

Co-authored-by: Oliver Huettenhofer oliver.huettenhofer@gmail.com
Co-authored-by: Oliver Hüttenhofer 168852439+ohuettenhofer@users.noreply.github.com