qutip

Use QuTiP's mesolve function with a Hamiltonian, initial state, and collapse operators representing dissipation channels. It returns density matrix evolution and expectation values for specified observables over a time list.

sesolve handles unitary evolution of pure states in closed systems. mesolve solves Lindblad master equations for mixed states with dissipation. mcsolve runs Monte Carlo quantum trajectories for individual jump realizations.

QuTiP focuses on continuous quantum dynamics, not circuit-based quantum computing. For quantum algorithms and hardware execution, use qiskit, cirq, or pennylane instead. The optional qutip-qip package adds basic gate operations.

Define the Hamiltonian as a list pairing operators with string expressions like 'cos(w*t)' or Python callback functions, passing parameters via the args dictionary. String format compiles for the fastest evaluation.

Large Hilbert space dimensions cause slowdowns. Truncate the Fock basis, use sesolve for pure states instead of mesolve, store only final states instead of all states, and use e_ops to compute observables directly.

Use the concurrence function on a two-qubit density matrix, or compute negativity via partial transpose. For pure bipartite states, trace out one subsystem with ptrace and calculate the von Neumann entropy of the reduced state.