A team of researchers working at Stanford University has extended the record for quantum superposition at the macroscopic level, from 1 to 54 centimeters. In their paper published in the journal Nature, the team describes the experiment they conducted, their results and also discuss what their findings might mean for researchers looking to find the cutoff point between superposition as it applies to macroscopic objects versus those that only exist at the quantum level. Nature has also published an editorial on the work done by the team, describing their experiment and summarizing their results.
Scientists entangling quantum particles and even whole atoms has been in the news a lot over the past couple of years as experiments have been conducted with the goal of attempting to better understand the strange phenomenon—and much has been learned. But, as scientists figure out how to entangle two particles at ever greater distances apart there has come questions about the size of objects that can be entangled. Schrödinger's cat has come up in several such discussions as theorists and those in the applied fields seek to figure out if it might be truly possible to cause a whole cat to actually be in two places at once. In this new work, the team at Stanford has perhaps muddied the water even more as they have extended the record for supposition from a mere one centimeter to just over half a meter.
They did it by creating a Bose-Einstein condensate cloud made up of 10,000 rubidium atoms (inside of a super-chilled chamber) all initially in the same state. Next, the used lasers to push the cloud up into the 10 meter high chamber, which also caused the atoms to enter one or the other of a given state. As the cloud reached the top of the chamber, the researchers noted that the wave function was a half-and-half mixture of the given states and represented positions that were 54 centimeters apart. When the cloud was allowed to fall back to the bottom of the chamber, the researchers confirmed that atoms appeared to have fallen from two different heights, proving that the cloud was held in a superposition state.
The team acknowledges that while their experiment has led to a new record for superposition at the macroscopic scale, it still was done with individual atoms, thus, it is still not clear if superposition will work with macroscopic sized objects.
Via Dr. Stefan Gruenwald