What’s the News: On a quest to discover at what size the kooky quantum physics that governs atoms (teleporting!) gives way to the ho-hum classical physics that governs humans (no teleporting), scientists have shown that if conditions are right, a molecule of a record 430 atoms can be in two states at once, like Schrödinger’s infamous cat. For the last three decades, researchers have been watching progressively larger objects under special conditions to see how big of an item they can catch showing quantum behavior. This molecule, which was created by a team at University of Vienna and their collaborators for the experiment, is the largest on record. How the Heck: The researchers shot a beam of molecules through a series of three sets of slits---an updated and modified version of the classic double-slit experiment---and measured exactly where the molecules arrived at the end of the beam. Graphs of where the molecules arrived show a fluctuating pattern indicating interference between the parts of the beam going through different slits. Since the molecules interfered with each other (not something well-behaved classical molecules do) that means they went through the slits in a superposition of multiple quantum states---the same way Schrödinger's cat is in a superposition of alive and dead states. What’s the Context:
Scientists who study this transition, called the “quantum-classical boundary,” seek to understand how classical physics arises from quantum physics. At some point between single atoms and the collections of 7 x 10^27 atoms that make up humans, the cumulative effect of all those atoms interacting with each other and their environment becomes the effect we call classical physics.
Physicists call the phenomenon behind the quantum-classical boundary “decoherence.” Simply put, as soon as atoms start to interact irreversibly with objects close to them, be they other atoms or some aspect of their environment, their zany superpowers seem to disappear.
A major breakthrough in this field came in 1999, when Anton Zeilinger and his team at the University of Vienna found that buckyballs---soccer ball–shaped molecules of 60 carbon atoms---had properties of both waves and particles, a distinctly quantum trait. The lead author on this paper, Markus Arndt, was on that team.
The Future Holds: More experiments, larger objects. Arndt, in an interview with Nature News, said that although custom-made molecules are easiest to handle, researchers could look for quantum behavior in viruses, pending the resolution of some technical difficulties. Reference: Gerlich, S. et al. Quantum interference of large organic molecules. Nat. Commun. 2:263 doi: 10.1038/ncomms1263.
