In a groundbreaking experiment, scientists at the University of Vienna have managed to reverse time in a quantum system and return a photon to its original state. This means that the system can also reverse developments that are unknown. In physics, processes have a certain direction of time. However, in the quantum theory, different rules apply, and it is impossible to observe changes in the temporal sequence of a quantum system and reverse the process. The researchers used a rewinding protocol to reverse the development of the photon’s polarization, which allowed them to reverse the process without knowing the initial and final state of the photon.
The rewinding protocol was developed by theoretical physicist Miguel Navascues from the Institute for Quantum Optics and Quantum Information (IQOQI) of the Austrian Academy of Sciences (ÖAW). The protocol allows changes in a quantum system to be reversed over time by coupling the development of the system to another development. The researchers used a single photon as a quantum system, and they overlaid the development of the photon’s polarization with another polarization, making it impossible to know which process came first. The application of the quantum switch twice caused time to run backward within the quantum system, and the photon returned to its original state.
The researchers believe that their discovery is “fundamentally incredibly interesting” and could have technological applications. For example, a rewinding protocol could be integrated into a quantum processor to reverse errors or unwanted developments. The experiment is a significant step forward in quantum mechanics and could have far-reaching implications for the future of technology.
