# Don’t let yourself get confused by these 4 Quantum Mechanics misconceptions

(ORDO NEWS) — Quantum mechanics, the theory that governs the microcosm of atoms and particles, certainly has an X factor.

Unlike many other areas of physics, it is bizarre and illogical, which makes it dazzling and intriguing.

But the debate about quantum mechanics – whether it’s in forums, in the media, or in science fiction – can often get tangled up in a series of enduring myths and misconceptions. Here are four.

#### 1/ A cat can be dead and alive

Erwin Schrödinger probably never could have predicted that his thought experiment, Schrödinger’s cat, would become an Internet meme in the 21st century.

This suggests that Lucky Cat, stuck in a box with a kill switch triggered by a random quantum event – such as radioactive decay – could be both alive and dead at the same time unless we open the box to check.

We have long known that quantum particles can be in two states—for example, in two places—simultaneously. We call this superposition.

Scientists were able to show this in the famous double slit experiment, where a single quantum particle, such as a photon or an electron, can pass through two different slits in a wall. simultaneously. How do we know this?

In quantum physics, the state of each particle is also a wave. But when we send a stream of photons, one after the other, through the slits, a pattern of two waves is created on the screen behind the slit, interfering with each other.

Since each photon did not have to interfere with other photons when it passed through the slits, this means that it must have passed through both slits at the same time, interfering with itself (image below).

However, for this to work, the states (waves) in the superposition of a particle passing through both slits must be “coherent” have well-defined relationships with each other.

These superposition experiments can be done with objects of ever-increasing size and complexity.

One famous experiment by Anton Zeilinger in 1999 demonstrated quantum superposition with large carbon-60 molecules known as “buckyballs”.

So what does this mean for our poor cat? Is he really both alive and dead until we open the box?

Obviously, a cat is nothing more than a single photon in a controlled laboratory environment, it is much larger and more complex.

Any coherence that the trillions and trillions of atoms that make up a cat can have with each other is extremely short-lived.

This does not mean that quantum coherence is impossible in biological systems. , it just doesn’t usually apply to large creatures like cats or humans.

#### 2/ Simple analogies can explain entanglement

Entanglement is a quantum property that links two different particles in such a way that if you measure one, you automatically and instantly know the state of the other, no matter how far apart they are.

Common explanations for this usually involve everyday items from our classical macroscopic world, such as dice, cards, or even pairs of different colored socks.

For example, imagine you are telling your friend that you put a blue card in one envelope and an orange card in another. If your friend takes and opens one of the envelopes and finds a blue card, he will know that you have an orange card.

But to understand quantum mechanics, you have to imagine two cards inside envelopes. in joint superposition, which means they are both orange and blue (specifically orange/blue and blue/orange).

Opening one envelope reveals one random color. But opening the second still always shows the opposite color because it is “ghostly” associated with the first card.

You can force maps to display in a different set of colors, akin to doing a different type of measurement. . We could open the envelope by asking the question, “Are you a green card or a red card?”

The answer would again be random: green or red. But most importantly, if the cards were mixed up, the other card would still always give the opposite result when the same question was asked.

Albert Einstein tried to explain this with classical intuition, suggesting that the cards might have been equipped with a hidden internal set of instructions that told them what color to appear when answering a certain question.

He also dismissed the apparent “ghostly” action between the cards, which apparently allows them to instantly affect each other, which could mean faster-than-light communication, which is forbidden by Einstein’s theories.

However, Einstein’s explanation was subsequently ruled out by Bell’s theorem (a theoretical test created by physicist John Stuart Bell) and the experiments of the 2022 Nobel laureate. laureates. The idea that measuring one entangled card changes the state of another is wrong.

Quantum particles just mysteriously correlate in ways that we can’t describe with ordinary logic or language they don’t interact, and also with hidden code, as Einstein thought.

So forget everyday objects when you think about entanglement.

#### 3/ Nature is unreal and “non-local”

It is often said that Bell’s theorem proves that nature is not “local,” that an object is not merely directly influenced by its immediate environment. Another common interpretation is that it implies that the properties of quantum objects are not “real”, that they do not exist prior to measurement.

But Bell’s theorem only allows us to say that quantum physics means that nature does not exist. both real and local if we allow several other things at the same time.

These assumptions include the idea that dimensions only have one outcome (rather than multiple, perhaps in parallel worlds), that cause and effect flow forward in time, and that we don’t live in a “clockwork universe” in which everything was predetermined. from time immemorial.

Despite Bell’s theorem, nature can very well be real and local if you let some other things that we think of as common sense, like the forward movement of time, be violated. We hope that further research will reduce the number of potential interpretations of quantum mechanics.

However, most of the possible options – for example, time running backwards, or the absence of free will – are no less absurd than the rejection of the concept of local reality.

#### 4/ Nobody understands quantum mechanics

A classic quote (attributed to physicist Richard Feynman, but in this form also paraphrasing Niels Bohr) suggests, “If you think you understand quantum mechanics, you don’t.”

This view is widely held in society. Quantum physics is allegedly impossible to understand, including physicists. But from a 21st century perspective, quantum physics is neither mathematically nor conceptually particularly challenging for scientists.

We understand it very well, to such an extent that we can predict quantum phenomena with high accuracy, simulate very complex quantum phenomena. systems and even start building quantum computers.

Superposition and entanglement, when explained in the language of quantum information, require no more than high school mathematics. Bell’s theorem does not require any quantum physics at all. It can be deduced in several lines using probability theory and linear algebra.

The real difficulty perhaps lies in how to reconcile quantum physics with our intuitive reality. The absence of all answers will not prevent us from making further progress in the field of quantum technologies. We can just shut up and count.

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