Can Quantum Computing Reveal the True Meaning of Quantum Mechanics?

The above-titled article commences with an overview of different interpretations of quantum probability.

There are different interpretive camps within quantum mechanics, which have squabbled with each other for generations, even though, by design, they all lead to the same predictions for any experiment that anyone can imagine doing. One interpretation is Many Worlds... A second interpretation is Bohmian mechanics... A third option is Niels Bohr’s original “Copenhagen Interpretation”...

The author then makes a very interesting point.

But wait: if these interpretations (and others that I omitted) all lead to the same predictions, then how could we ever decide which one is right? More pointedly, does it even mean anything for one to be right and the others wrong, or are these just different flavors of optional verbal seasoning on the same mathematical meat?

He proposes that the infant science of quantum computing might help shed some light on the problem.

A useful quantum computer would be the most dramatic demonstration imaginable that our world really does need to be described by a gigantic amplitude wave, that there’s no way around that, no simpler classical reality behind the scenes.

He then goes on to discuss what success in quantum computing might tell us about the different interpretations.

Those interested in the implications quantum theory has for our models of reality will find this article fascinating, I think.

a reply to: Astyanax

Maybe a truly self aware quantum machine would be capable of understanding another machines creation of virtual realities? Sounds plausible to me since the quantum AI would be seeing the universe as code rather than what it isn't.

Cheers - Dave

a reply to: Astyanax

A third option is Niels Bohr’s original “Copenhagen Interpretation,” which says—but in many more words!—that the amplitude wave is just something in your head, a tool you use to make predictions. In this view, “reality” doesn’t even exist prior to your making a measurement of it—and if you don’t understand that, well, that just proves how mired you are in outdated classical ways of thinking, and how stubbornly you insist on asking illegitimate questions.

Interesting article but this statement is misleading. Many pseudo-scientists to try claim the Copenhagen interpretation means there is no objective reality until we measure it, but that's not really the case. It says some things, such as the state of a small quantum scale object may be undetermined until it is measured and forced to take on a specific state, but it does not say everything exists in that fuzzy state while it's not being observed. First of all it's not even clear what an observer is, and I would strongly argue that any high energy objects can act as observers. And secondly, once the wave-function has been collapsed by making a measurement, the system will remain in that state so that if someone else looks they will see the same thing.

That would seem to imply we help create reality by making new observations and collapsing the wave-function, because before the measurement was made, it was just a cloud of probabilities. But I don't think that is really the case either, it really all boils down to decoherence and entanglement. We can make elementary particles and even larger molecules exist in a state of superposition by keeping them extremely isolated from their environment, but as soon as we let them interact with the high energy environment they become entangled with it and start to behave in a classical manner due to decoherence. Therefore the high energy environment is clearly acting as the observer and causing the superposition to collapse into a single position, conscious observers need not play any role.

Furthermore, high energy objects in the environment, for example the moon, must exist in a classical state even when we're not looking at them. It is only when you have a very simple isolated system that it will exhibit strange quantum behavior. If I have a large clump of gold in complete isolation it obviously wont start acting strangely, but if I have just one molecule of gold in isolation I will be able to measure it doing weird things, but that will stop if I don't keep it isolated from the environment. The problem in my mind with quantum computers is that we will never be able to keep the qubits isolated enough from the environment and each other to prevent decoherence, especially since we need to interact with the qubits in order to read their states.

But wait: if these interpretations (and others that I omitted) all lead to the same predictions, then how could we ever decide which one is right? More pointedly, does it even mean anything for one to be right and the others wrong, or are these just different flavors of optional verbal seasoning on the same mathematical meat?

Well as the article mentions, some interpretations such as Bohmian mechanics can and has been discredited by experimental evidence. But it's not so clear other interpretations like the Many Worlds interpretation and the Copenhagen interpretation predict different things, for me it's really the implications which matter. I prefer not to believe in the Many Worlds interpretation because it suggests a huge or infinite number of other worlds exist in which I've made terrible decisions, and it also predicts that the most unlikely things will happen in some of those worlds, for example I might be batman in another world, which doesn't strike me as a rational view of reality. In some sense the Many Worlds interpretation is completely deterministic and it makes my choices seem irrelevant because I'm always making every possible choice simultaneously.

I dislike Bohmian mechanics (aka pilot wave theory) for similar reasons, it implies my actions are irrelevant because they're already predetermined. It is essentially a hidden variable theory which tries to apply a completely deterministic set of rules to quantum mechanics and get rid of the randomness, and that's one reasons it's an easy interpretation to discredit. I tend to lean towards the Copenhagen interpretation or variants of it, but I don't interpret it as meaning conscious observers play some important role, I interpret it as meaning probability plays an important role. I watched a very interesting video on the Four Types of Multiverse a few weeks ago. In that video Tony Padilla sums up his concerns with the many-worlds interpretation, which mirrors my exact feelings on the issue.

There's a few things I don't like about this. Firstly, when ever you have a split, well when does the split occur, at which point does the split occur precisely, when is that? I mean there's already time uncertainty in quantum mechanics so when does the split occur, that's not really clearly answered.

Secondly, if you do these splits, you're increasing the number of states suddenly, you're increasing the size of the space that describes the quantum system and that doesn't seem satisfactory either. The problem I have is that this was originally introduced, well people like to think about it because they're unconfortable with the idea of the collapse of the wave-function, the idea that when you open the box the cat is either dead or alive and not both.

But we actually understand why that is now, it's to do with a process called decoherence where the large environment outside of the box starts to mix up with the cat in such a way that the overlap region between cat dead and cat alive, because of the large environmental system outside, just gets made very small.

So if we're ok with wave-function collapse because we understand it through this decoherence, what's wrong with the idea that nature is probabilistic? Why do we have to have that every possibility is realized? Quantum mechanics is probabilistic, that's the way nature is, and just because our classical intuition tells us that we enjoy a deterministic existence, that doesn't mean quantum mechanics has to behave like that, it doesn't mean nature has to behave like that, it just means day to day that's how it seems to behave, but truly it's probabilistic. And that's fine, ok. It doesn't mean that every possibility has to be realized.