Research Suggests Gravity Destroys Schrödinger’s Cat

Schrödinger's Cat
Schrödinger's Cat

One of the best known examples of the oddities of quantum physics is the so-called Schrödinger’s Cat. In this thought experiment, the cat is deemed to be neither dead nor alive, but rather existing in a so-called quantum superposition of both states; that is, the cat is simultaneously dead and alive. It’s a provocative image because, clearly, such superpositions do not exist at the macro level of everyday experiences. However, they do exist at the micro level of quantum reality. The puzzle is how the two relate. In other words, why are quantum superpositions not observed on a macro level?

Physicists usually assume that quantum-level superpositions collapse into definite states at the macro level because of interactions between quantum systems with surrounding particles. This loss of quantumness is known as decoherence. But as recently reported in Nature Physics, an international collaboration of researchers from the universities of Vienna, Harvard, and Queensland, headed by John Templeton Foundation grantee Caslav Brukner, has offered a new possibility. The work finds that a gravitational effect of general relativity, known as time dilation, plays a major role in quantum effects.

Time dilation is the observed slowing of time due to the presence of massive objects. For example, clocks run marginally faster at the top of the Mount Everest than those at the sea level because the gravitational force at the sea level is stronger than at the top of Mount Everest. Generally speaking, the gravitational force is decreasing with the distance from the sea level.

The effect of time dilation is being felt at the atomic level because molecules “jitter.” The jittering is slower when molecules are closer to nearby massive objects, destroying quantum superposition.

It’s an unexpected result since gravity is usually disregarded at the quantum level, but now seems to have a significant impact at the smallest scales. “It remains to be seen what the results imply on cosmological scales, where gravity is much stronger,” adds Brukner. As Scientific American also noted, the new effect doesn’t account for one of the main goals of 21st century physics: how to unite the theories of relativity with those of quantum mechanics. On the other hand, it might open a new perspective on how two of the most important physical theories can be unified.