  Wheeler's delayed-choice experiment delays the decision to observe either the
wave or particle behavior of a photon until after it has entered the
interferometer, and the quantum delayed-choice experiment provides the
possibility of observing the wave and particle behavior simultaneously by
introducing quantum control device. We here propose a modified quantum
delayed-choice experiment without quantum control or entanglement assistance,
in which a photon can be prepared in a wave-particle superposition state and
the morphing behavior of wave-to-particle transition can be observed easily. It
is demonstrated that the presented scheme can allow us to rule out classical
hidden variable models in a device-independent manner via violating dimension
witness. We also extend the scheme to the situation of two degrees of freedom,
first constructing a hybrid quantum delayed-choice experiment which enables
simultaneous observation of a photon's wave and particle behaviors in different
degrees of freedom, and then proposing a scheme to prepare the single-photon
wave-particle entanglement. This study is not only meaningful to explore the
wave and particle properties of photons, but also provides potential for the
research of the single-particle nonlocality from the perspective of the
wave-particle degree of freedom.
