Worked on the Qiskit/qiskit repository to improve the correctness and stability of quantum state evolution in Python. Addressed a bug in the Statevector.evolve method by ensuring that input states are not mutated during evolution, which helps prevent unintended side effects in quantum circuit simulations. Enhanced global phase handling by separating data arrays for phase operations, reducing the risk of accidental modifications to shallow copies. Expanded the regression test suite to verify these behaviors and updated release notes to document the changes. Focused on Python, quantum computing concepts, and rigorous testing practices to deliver more reliable simulation tools.