Humans tend to think they have a pretty good handle on how the physical world operates, but things get unspeakably weird at the small scale. Particles aren’t always particles, and sometimes those particles (or waves) behave in bizarre, counterintuitive ways. One of the strangest features of physics is quantum entanglement, and scientists from the University of Glasgow have just captured the first photo demonstrating the effect.
When two particles or molecules become entangled on a quantum level, they share one or more properties such as spin, polarization, or momentum. This effect persists even if you move one of the entangled objects far away from the other. Einstein famously called entanglement “spooky action at a distance.” Einstein felt the existence of entanglement meant there were gaping holes in quantum mechanical theory.
Scientists have successfully demonstrated quantum entanglement with photos, electrons, molecules of various sizes, and even very small diamonds. The University of Glasgow study is the first ever to capture visual evidence of entanglement, though. The experiment used photons in entangled pairs and measured the phase of the particles — this is known as a Bell entanglement.
The team produced photons with an ultraviolet laser, passing them through a crystal that causes some of the photos to become entangled. A beam splitter turned the beam into two equal “arms” with some of the entangled photos going down different paths. Since they were entangled, they continued to share the same phase even after being separated.
The experimental setup. The beam starts in the lower left, splits in the middle, and the left “arm” goes through phase filters.
One of those photons passes through a liquid crystal material that runs it through four phase transitions (0, 45, 90, and 135-degrees). The team used a highly sensitive camera to capture images of the entangled photon that hadn’t gone through the filter. However, it showed the same phase transitions as its partner. The image above shows the entangled pair at a 45-degree phase.
Scientists believe that quantum entanglement could have applications in quantum computing, data transmission, and even teleportation. For any of that to work, we need to study entanglement in much greater detail. The University of Glasgow experiment may open the door to new types of imaging that help us come to grips with that spooky action at a distance.