This page describes naming rules and conventions that exist throughout Cirq. These rules are important in order to maintain a consistent interface that is easy to use. By using consistent naming we can reduce cognitive load on users and developers. Please try to use these terms when writing code.

If you have suggestions for improvements or changes, please create a PR to modify this list or open an issue.

Quantum computing terms

Use state_vector to describe a pure state. Do not use wavefunction, wave_function, or state for this object (state is too overloaded).
If the object is an array or possibly a computational basis state (given by an int), use state_rep or, if it is the initial state of a system initial_state. A function argument (state_vector, state_rep, or initial_state) should permit any of the possible representations of a state: A numpy array, a numpy tensor, an integer representing a qubit-system's computational basis state, a sequence of n integers representing a qudit's basis state, or a cirq.ProductState. The type annotation should be cirq.STATE_VECTOR_LIKE and you should use cirq.to_valid_state_vector to canonicalize as a numpy array of amplitudes. If a function expects a numpy array of amplitudes, its type annotation should be np.ndarray.

Use density_matrix to describe a mixed state that is passed in as a numpy matrix or numpy tensor. Do not used mixed_state, density_operator, or state.