How would my life be different without quantum entanglement?

Question

What would happen if for some reason quantum entanglement were suddenly turned off? By "turned off", let's say that every entangled state is immediately replaced with a separable (but still classically correlated) state, e.g. a Bell state $(|00\rangle+|11\rangle)/\sqrt2$ might be replaced with $(|00\rangle\langle 00|+|11\rangle\langle 11|)/2$. The laws of quantum mechanics still hold.

What effect would this have on my everyday life? Could I still get out of bed, have a shower, take the bus to work, etc.? I'm not interested in the effect it would have on physics experiments such as Bell nonlocality no longer being detectable. I am interested in my everyday life as a non-physicist.

I have seen this similar question and find the answers given rather unsatisfactory. I understand that this scenario doesn't really make sense, since if the laws of quantum mechanics still hold then there will necessarily be entanglement, e.g. solving the Schrodinger equation to find the ground state of helium. I don't think this should make it impossible to understand the essence of the question and give some insight into how entanglement affects everyday life (if indeed it does).

Edit: another way of understanding what I mean by this question is "what processes in my everyday life rely on entanglement?".

Answer 1

The question assumes that quantum entanglement actually happens the way it has been described by quantum mathematics. Which may or may not be true. All is not set yet. Leaving that aside -

In any case, entanglement is not a law in itself, it is a phenomenon. It is a consequence of basic underlying laws at quantum level. For example, anti correlation of spin is a phenomenon caused by law of conservation of angular momentum. Then there is statistical correlation of spin. And there are other multiple entangled properties.

You can not take entanglement away without modifying those underlying laws. But then modifying the underlying laws will not affect only entanglement phenomena, it can impact pretty much everything in the universe.

In fact, There may be just one most fundamental law of the universe, and changing any laws may not be possible without changing the most fundamental law. Changing that law would change everything. As knzhou rightly said, "physics is woven too tightly together to just rip out a piece of it"

Answer 2

I will turn my comment to an answer, in reality answering your statement in the comments:

Thus I am asking "what everyday processes require quantum entanglement rather than just classical correlation?"

Classical probabilistic analysis depends on classical dynamics, the emergence of entropy from statistical mechanics is a good example.

There have been and there continue to exist efforts to show that the quantum dynamics emerges from an underlying level of classical dynamics. A good example of this is Bohmian mechanics. It is able to give the same results as non relativistic quantum mechanics, i.e. bound quantized states. Afaik it fails in relativistic quantum mechanics.

In your question you are not proposing that the known particles are composite or have an underlying level of complexity that might lead to equations with emergent bound quantized states. Just having classical probabilities in place of quantum mechanical ones, which is what will happen if the QM phases are not there, will lead to continuum four vector states. The bound states have probability 1, which is not possible in classical probabilities for the same set up of particles, and the forces as we have found them. I cannot see how it could be contrived , unless with a substructure a la Bohm.

Answer 3

Entanglement manifests via correlations. If you can get rid of entanglement while keeping those correlations, I guess nothing will change in your life.

So what is the question exactly? If it is, "do we know how to reduce quantum correlations to classical ones?" (ie. do we have a proper hidden variables theory), the answer is no (at this time, no such theory is convincing).

If it is, "does quantum mechanics still hold in the absence of entanglement?" then the answer is also no, contrary to what is assumed in the question. Entanglement is not a peripherical part of quantum mechanics, it is a deep aspect of it.

To the question "what processes in my everyday life rely on entanglement?", rephrased as per the above as "what processes in my everyday life rely on quantum correlations?", the answer is: all of them, because all physical processes are ultimately described by quantum mechanics, and I don't see what it would mean to accept quantum mechanics without accepting quantum correlations.

Still there is an interesting twist here: physics has progressed by the analysis and description of causal correlations. So all common physical processes, and naturally all classical ones, can be described without the need to introduce non-causal correlations, which is why it is hard to pinpoint a specific process directly requiring quantum correlations to be explained.

Answer 4

Entanglement is fundamental to our understanding of the behavior of matter. If you get rid of entanglement then matter must behave differently. Which would break the processes that keep your body working.

Actually, entanglement is so deep in quantum mechanics that it's not clear how you could remove it without just throwing out the whole theory. It's a bit like asking "How would my life be different without angular momentum?". And it's not like we can just go back to classical mechanics, because then electron orbits would decay.

So I guess I would describe your life under no-entanglement conditions as... short? Everyone everywhere dying in a fraction of a second because electron transport stopped working or something.