New research may be key to quantum weirdness.

Is the cat dead or alive? Physicist Howard J. Wisemen may have an answer to this question* *by modeling a finite number of possible worlds.

Quantum mechanics is not an easy dinner table conversation, so it’s difficult to imagine that there are many alternative theories. Quantum mechanics provides us with the most detailed description of nature. However, there are many different variations on quantum mechanics. The debate involves which picture fits nature the most realistically. In other words, which theory gives us the closest picture of what nature really is like?

This is the question physicist Howard J. Wiseman is asking in his new article “Quantum phenomena modeled by interactions between many classical worlds” published in the journal *Physics Review X.*

In the introduction of the article, Wisemen summarizes the substance of the paper.

“The world we experience is just one of an enormous number of essentially classical worlds, and all quantum phenomena arise from a universal force of repulsion that prevents worlds from having identical physical configurations,” said Wiseman.

Essentially, what he proposes is imagining there exists many universes, to which we have no direct access. There could be universes where there are completely different laws of nature, a universe where you don’t exist, etc. Older models proposed an infinite number of universes where all possible worlds that could exist, do exist. This is difficult because scientists usually go for theories that explain the data the simplest and an infinite number of possible worlds is certainly not simple. Wiseman believes that his theory doesn’t run into this problem because he can point to a finite number of possible worlds, thus avoiding the infinite.

Wisemen and his colleagues believe that the problems in quantum mechanics are solved by their model.

“This picture is all that is needed to explain bizarre quantum effects such as particles that tunnel through solid barriers and wave behavior in double-slit experiments,” said Wiseman. In other words, one can imagine that there are interacting parallel worlds in which two things are happening at once and our inability to distinguish which state is actual is only due to our ignorance of the states going on in the other world. For example, the double slit experiment shows that particles act like waves when not observed and like matter when they are observed. This is a very bizarre feature of quantum mechanics: how can light be both matter and a wave? Wisemen believes his theory answers this by imagining a world where light is a wave and another world where light is matter.

The “mainstream” theory is known as the Copenhagen interpretation of quantum mechanics. This interpretation is the version widely considered as the most accurate in experimental and theoretical settings. However, the problem is that this interpretation leads to all sorts of bizarre consequences such as superpositioning. This is a difficult concept to understand but it is simply laid out in Erwin Schrödinger’s thought experiment, Schrödinger’s cat.

Essentially, the thought experiment asks you to imagine that there is some quantum process that experiences superpositioning, which means two states of affairs can exist at the same time. This occurs until the moment of observation when the observer will see only one of the two states, in which “the wave function collapses” and one of the two states is actualized to the observer. Schrödinger wanted you to imagine that some physical system which contained a quantum process was hooked to a vial of poison and a cat was placed into a box with this apparatus. When the quantum process occurred, the vial of poison would break open and the cat would die. However, since we cannot know if the quantum process occurred until observation, we must say the state is in a superposition. Thus, the cat must also be in a superposition of being both dead and alive until we observe it.

Einstein famously spoke about the absurdity of this consequence by saying that the moon’s existence is not dependent on his observation of it. This is clearly a bizarre consequence, but at the same time, we find ourselves using this model as the most reliable quantum model.

We see the appeal of finding simpler explanations. Clearly, Wisemen’s proposal is an interesting one. The challenge will be to see whether or not other physicists will buy into the idea that a multi-world theory is more like the real world than a world where these kind of bizarre physical occurrences exist. Wiseman admits that his quantum theory has a long way to go until it is properly worked out.