Quantum twisted Loong confirms the physical reality of wavefunctions

Wavefunctions play a crucial role in quantum dynamics, offering a correct probability list of measurement outcomes. However, researchers still debate whether wavefunctions describe the reality of quantum existence and dynamic trajectory. In various delayed-choice experiments dedicated to this issue, the Copenhagen interpretation denied the reality of wavefunctions for avoiding the causality paradox in which a choice made in the present alters a photon's past behavior. Determinists argued that the past of photons should be realistic and deterministic prior to the detection. As Einstein's famous question asks, do you really believe the moon exists only when you look at it?

Recently, to address this long-standing issue, Profs. Bao-Sen Shi's research group from the University of Science and Technology of China and collaborators conducted a quantum twisted double-slit experiment to extract the propagation history of photons after detections. First, the state (wavefunction) of signal photons diffracted from the twisted double slits was transformed into a superposition state between different OAM modes and Gaussian mode; second, the photons were observed only in Gaussian mode (selecting particle behavior); and then, a Hong-Ou-Mandel (HOM) interference between signal and reference photons provided the arrival times of signal photons that allowed the researchers to investigate the photons' propagation history.

The results obtained from the experiment revealed that the nature of the photon prior to the measurement is pre-existing, just as described by the wavefunction. Thus, the physical reality and nonlocality of wavefunctions are confirmed. This finding clarifies the long-held misunderstanding of the role of wavefunctions and their collapses in the evolution of quantum entities. In addition, they present a cartoon titled "Quantum Twisted Loong" (Fig. 5), to illustrate the propagation behavior of photons in a double-slit apparatus. Unlike the cartoon titled "Great Smoky Dragon" created by Miller and Wheeler in 1983, as shown in Fig. 2, where the body of the dragon is unknown and smoky, the body of Loong is deterministic, i.e., the two bodies coexist simultaneously (representing wave nature) before their collapse.

More information:
Zhi-Yuan Zhou et al, Quantum twisted double-slits experiments: confirming wavefunctions' physical reality, Science Bulletin (2017). DOI: 10.1016/j.scib.2017.08.024

Provided by Science China Press