Are quantum states real? This most fundamental question in quantum mechanics has not yet been satisfactorily resolved, although its realistic interpretation seems to have been rejected by various delayedchoice experiments. Here, to address this long-standing issue, we present a quantum twisted double-slit experiment. By exploiting the subluminal feature of twisted photons, the real nature of a photon during its time in flight is revealed for the first time. We found that photons' arrival times were inconsistent with the states obtained in measurements but agreed with the states during propagation. Our results demonstrate that wavefunctions describe the realistic existence and evolution of quantum entities rather than a pure mathematical abstraction providing a probability list of measurement outcomes. This finding clarifies the long-held misunderstanding of the role of wavefunctions and their collapse in the evolution of quantum entities.
Controlled obtaining of orbital angular momentum (OAM) modes of light at high power over arbitrary orders has important implications for fiiture classical and quantum systems. Appreciable optical amplification has recently been observed for low-order or specific-order OAM modes. However, large amplification of high-order OAM modes still remains challenging. Here we report on flat-gain amplification of arbitrary OAM modes via Brillouin interactions and demonstrate that the OAM modes with various orders can be efficiently and relatively uniformly amplified by imaging the wave source of OAM mode propagation in a nonlinear medium.Meanwhile, the propagation properties of beams carrying OAM with arbitrary modes are high-fidelity maintained.This work provides a practicable way to flatten the mode gain and represents a crucial necessity to realize OAM mode filters with controllable mode gain bandwidth.
