code: def zero_state(qubits: Union[int, Qubits]) -> State:
      
      N, qubits = qubits_count_tuple(qubits)
      ket = np.zeros(shape=[2] * N)
      ket[(0,) * N] = 1
      return State(ket, qubits)
docs: Return the all-zero state on N qubits