I am factually correct, I am not here to “debate,” I am telling you how the theory works. When two systems interact such that they become statistically correlated with one another and knowing the state of one tells you the state of the other, it is no longer valid to assign a state vector to the system subsystems that are part of the interaction individually, you have to assign it to the system as a whole. When you do a partial trace on the system individually to get a reduced density matrix for the two systems, if they are perfectly entangled, then you end with a density matrix without coherence terms and thus without interference effects.

This is absolutely entanglement, this is what entanglement is. I am not misunderstanding what entanglement is, if you think what I have described here is not entanglement but a superposition of states then you don’t know what a superposition of states is. Yes, an entangled state would be in a superposition of states, but it would be a superposition of states which can only be applied to both correlated systems together and not to the individual subsystems.

Let’s say R = 1/sqrt(2) and Alice sends Bob a qubit. If the qubit has a probability of 1 of being the value 1 and Alice applies the Hadamard gate, it changes to R probability of being 0 and -R probability of being 1. In this state, if Bob were to apply a second Hadamard gate, then it undoes the first Hadamard gate and so it would have a probability of 1 of being a value of 1 due to interference effects.

However, if an eavesdropper, let’s call them Eve, measures the qubit in transit, because R and -R are equal distances from the origin, it would have an equal chance of being 0 or 1. Let’s say it’s 1. From their point of view, they would then update their probability distribution to be a probability of 1 of being the value 1 and send it off to Bob. When Bob applies the second Hadamard gate, it would then have a probability of R for being 0 and a probability of -R for being 1, and thus what should’ve been deterministic is now random noise for Bob.

Yet, this description only works from Eve’s point of view. From Alice and Bob’s point of view, neither of them measured the particle in transit, so when Bob received it, it still is probabilistic with an equal chance of being 0 and 1. So why does Bob still predict that interference effects will be lost if it is still probabilistic for him?

Because when Eve interacts with the qubit, from Alice and Bob’s perspective, it is no longer valid to assign a state vector to the qubit on its own. Eve and the qubit become correlated with one another. For Eve to know the particle’s state, there has to be some correlation between something in Eve’s brain (or, more directly, her measuring device) and the state of the particle. They are thus entangled with one another and Alice and Bob would have to assign the state vector to Eve and the qubit taken together and not to the individual parts.

Eve and the qubit taken together would have a probability distribution of R for the qubit being 0 and Eve knowing the qubit is 0, and a probability of -R of the qubit being 1 and Eve knowing the qubit is 1. There is still interference effects but only of the whole system taken together. Yet, Bob does not receive Eve and the qubit taken together. He receives only the qubit, so this probability distribution is no longer applicable to the qubit.

He instead has to do a partial trace to trace out (ignore) Eve from the equation to know how his qubit alone would behave. When he does this, he finds that the probability distribution has changed to 0.5 for 0 and 0.5 for 1. In the density matrix representation, you will see that the density matrix has all zeroes for the coherences. This is a classical probability distribution, something that cannot exhibit interference effects.

Bob simply cannot explain why his qubit loses its interference effects by Eve measuring it without Bob taking into account entanglement, at least within the framework of quantum theory. That is just how the theory works. The explanation from Eve’s perspective simply does not work for Bob in quantum mechanics. Reducing the state vector simultaneously between two different perspectives is known as an objective collapse model and makes different statistical predictions than quantum mechanics. It would not merely be an alternative interpretation but an alternative theory.

Eve explains the loss of coherence due to her reducing the state vector due to seeing a definite outcome for the qubit, and Bob explains the loss of coherence due to Eve becoming entangled with the qubit which leads to decoherence as doing a partial trace to trace out (ignore) Eve gives a reduced density matrix for the qubit whereby the coherence terms are zero.

You can break elliptic curve cryptography with quantum computers. Post-quantum cryptography is instead based on something called the lattice problem, sometimes called lattice-based cryptography.

Personally, I think there is a much bigger issue with the quantum internet that is often not discussed and it’s not just noise.

Imagine, for example, I were to offer you two algorithms. One can encrypt things so well that it would take a hundred trillion years for even a superadvanced quantum computer to break the encryption, and it almost has no overhead. The other is truly unbreakable even in an infinite amount of time, but it has a huge amount of overhead to the point that it will cut your bandwidth in half.

Which would you pick?

In practice, there is no difference between an algorithm that cannot be broken for trillions of years, and an algorithm that cannot be broken at all. But, in practice, cutting your internet bandwidth in half is a massive downside. The tradeoff just isn’t worth it.

All quantum “internet” algorithms suffer from this problem. There is always some massive practical tradeoff for a purely theoretical benefit. Even if we make it perfectly noise-free and entirely solve the noise problem, there would still be no practical reason at all to adopt the quantum internet.

The problem with the one-time pads is that they’re also the most inefficient cipher. If we switched to them for internet communication (ceteris paribus), it would basically cut internet bandwidth in half overnight. Even moreso, it’s a symmetric cipher, and symmetric ciphers cannot be broken by quantum computers. Ciphers like AES256 are considered still quantum-computer-proof. This means that you would be cutting the internet bandwidth in half for purely theoretical benefits that people wouldn’t notice in practice. The only people I could imagine finding this interesting are overly paranoid governments as there are no practical benefits.

It also really isn’t a selling point for quantum key distribution that it can reliably detect an eavesdropper. Modern cryptography does not care about detecting eavesdroppers. When two people are exchanging keys with a Diffie-Hellman key exchange, eavesdroppers are allowed to eavesdrop all they wish, but they cannot make sense of the data in transit. The problem with quantum key distribution is that it is worse than this, it cannot prevent an eavesdropper from seeing the transmitted key, it just discards it if they do. This to me seems like it would make it a bit harder to scale, although not impossible, because anyone can deny service just by observing the packets of data in transit.

Although, the bigger issue that nobody seems to talk about is that quantum key distribution, just like the Diffie-Hellman algorithm, is susceptible to a man-in-the-middle attack. Yes, it prevents an eavesdropper between two nodes, but if the eavesdropper sets themselves up as a third node pretending to be different nodes when queried from either end, they could trivially defeat quantum key distribution. Although, Diffie-Hellman is also susceptible to this, so that is not surprising.

What is surprising is that with Diffie-Hellman (or more commonly its elliptic curve brethren), we solve this using digital signatures which are part of public key infrastructure. With quantum mechanics, however, the only equivalent to digital signatures relies on the No-cloning Theorem. The No-cloning Theorem says if I gave you a qubit and you don’t know it is prepared, nothing you can do to it can tell you its quantum state, which requires knowledge of how it was prepared. You can use the fact only a single person can be aware of its quantum state as a form of a digital signature.

The thing is, however, the No-cloning Theorem only holds true for a single qubit. If I prepared a million qubits all the same way and handed them to you, you could derive its quantum state by doing different measurements on each qubit. Even though you could use this for digital signatures, those digital signatures would have to be disposable. If you made too many copies of them, they could be reverse-engineered. This presents a problem for using them as part of public key infrastructure as public key infrastructure requires those keys to be, well, public, meaning anyone can take a copy, and so infinite copy-ability is a requirement.

This makes quantum key distribution only reliable if you combine it with quantum digital signatures, but when you do that, it no longer becomes possible to scale it to some sort of “quantum internet.” It, again, might be something useful an overly paranoid government could use internally as part of their own small-scale intranet, but it would just be too impractical without any noticeable benefits for anyone outside of that. As, again, all this is for purely theoretical benefits, not anything you’d notice in the real world, as things like AES256 are already considered uncrackable in practice.

Entanglement plays a key role.

Any time you talk about “measurement” this is just observation, and the result of an observation is to reduce the state vector, which is just a list of complex-valued probability amplitudes. The fact they are complex numbers gives rise to interference effects. When the eavesdropper observes definite outcome, you no longer need to treat it as probabilistic anymore, you can therefore reduce the state vector by updating your probabilities to simply 100% for the outcome you saw. The number 100% has no negative or imaginary components, and so it cannot exhibit interference effects.

It is this loss of interference which is ultimately detectable on the other end. If you apply a Hadamard gate to a qubit, you get a state vector that represents equal probabilities for 0 or 1, but in a way that could exhibit interference with later interactions. Such as, if you applied a second Hadamard gate, it would return to its original state due to interference. If you had a qubit that was prepared with a 50% probability of being 0 or 1 but without interference terms (coherences), then applying a second Hadamard gate would not return it to its original state but instead just give you a random output.

Hence, if qubits have undergone decoherence, i.e., if they have lost their ability to interfere with themselves, this is detectable. Obvious example is the double-slit experiment, you get real distinct outcomes by a change in the pattern on the screen if the photons can interfere with themselves or if they cannot. Quantum key distribution detects if an observer made a measurement in transit by relying on decoherence. Half the qubits a Hadamard gate is randomly applied, half they are not, and which it is applied to and which it is not is not revealed until after the communication is complete. If the recipient receives a qubit that had a Hadamard gate applied to it, they have to apply it again themselves to cancel it out, but they don’t know which ones they need to apply it to until the full qubits are transmitted and this is revealed.

That means at random, half they receive they need to just read as-is, and another half they need to rely on interference effects to move them back into their original state. Any person who intercepts this by measuring it would cause it to decohere by their measurement and thus when the recipient applies the Hadamard gate a second time to cancel out the first, they get random noise rather than it actually cancelling it out. The recipient receiving random noise when they should be getting definite values is how you detect if there is an eavesdropper.

What does this have to do with entanglement? If we just talk about “measuring a state” then quantum mechanics would be a rather paradoxical and inconsistent theory. If the eavesdropper measured the state and updated the probability distribution to 100% and thus destroyed its interference effects, the non-eavesdroppers did not measure the state, so it should still be probabilistic, and at face value, this seems to imply it should still exhibit interference effects from the non-eavesdroppers’ perspective.

A popular way to get around this is to claim that the act of measurement is something “special” which always destroys the quantum probabilities and forces it into a definite state. That means the moment the eavesdropper makes the measurement, it takes on a definite value for all observers, and from the non-eavesdroppers’ perspective, they only describe it still as probabilistic due to their ignorance of the outcome. At that point, it would have a definite value, but they just don’t know what it is.

However, if you believe that, then that is not quantum mechanics and in fact makes entirely different statistical predictions to quantum mechanics. In quantum mechanics, if two systems interact, they become entangled with one another. They still exhibit interference effects as a whole as an entangled system. There is no “special” interaction, such as a measurement, which forces a definite outcome. Indeed, if you try to introduce a “special” interaction, you get different statistical predictions than quantum mechanics actually makes.

This is because in quantum mechanics, every interaction leads to growing the scale of entanglement, and so the interference effects never go away, just spread out. If you introduce a “special” interaction such as a measurement whereby it forces things into a definite value for all observers, then you are inherently suggesting there is a limitation to this scale of entanglement. There is some cut-off point whereby interference effects can no longer be scaled passed that, and because we can detect if a system exhibits interference effects or not (that’s what quantum key distribution is based on), then such an alternative theory (called an objective collapse model) would necessarily have to make differ from quantum mechanics in its numerical predictions.

The actual answer to this seeming paradox is provided by quantum mechanics itself: entanglement. When the eavesdropper observes the qubit in transit, for the perspective of the non-eavesdroppers, the eavesdropper would become entangled with the qubit. It then no longer becomes valid in quantum mechanics to assign the state vector to the eavesdropper and the qubit separately, but only them together as an entangled system. However, the recipient does not receive both the qubit and the eavesdropper, they only receive the qubit. If they want to know how the qubit behaves, they have to do a partial trace to trace out (ignore) the eavesdropper, and when they do this, they find that the qubit’s state is still probabilistic, but it is a probability distribution with only terms between 0% and 100%, that is to say, no negatives or imaginary components, and thus it cannot exhibit interference effects.

Quantum key distribution does indeed rely on entanglement as you cannot describe the algorithm consistently from all reference frames (within the framework of quantum mechanics and not implicitly abandoning quantum mechanics for an objective collapse theory) without taking into account entanglement. As I started with, the reduction of the wave function, which is a first-person description of an interaction (when there are 2 systems interacting and one is an observer describing the second), leads to decoherence. The third-person description of an interaction (when there are 3 systems and one is on the “outside” describing the other two systems interacting) is entanglement, and this also leads to decoherence.

You even say that “measurement changes the state”, but how do you derive that without entanglement? It is entanglement between the eavesdropper and the qubit that leads to a change in the reduced density matrix of the qubit on its own.

You don’t have to be sorry, that was stupid of me to write that.

Because the same functionality would be available as a cloud service (like AI now). This reduces costs and the need to carry liquid nitrogen around.

Okay, you are just misrepresenting my argument at this point.

Why are you isolating a single algorithm? There are tons of them that speed up various aspects of linear algebra and not just that single one, and many improvements to these algorithms since they were first introduced, there are a lot more in the literature than just in the popular consciousness.

The point is not that it will speed up every major calculation, but these are calculations that could be made use of, and there will likely even be more similar algorithms discovered if quantum computers are more commonplace. There is a whole branch of research called quantum machine learning that is centered solely around figuring out how to make use of these algorithms to provide performance benefits for machine learning algorithms.

If they would offer speed benefits, then why wouldn’t you want to have the chip that offers the speed benefits in your phone? Of course, in practical terms, we likely will not have this due to the difficulty and expense of quantum chips, and the fact they currently have to be cooled below to near zero degrees Kelvin. But your argument suggests that if somehow consumers could have access to technology in their phone that would offer performance benefits to their software that they wouldn’t want it.

That just makes no sense to me. The issue is not that quantum computers could not offer performance benefits in theory. The issue is more about whether or not the theory can be implemented in practical engineering terms, as well as a cost-to-performance ratio. The engineering would have to be good enough to both bring the price down and make the performance benefits high enough to make it worth it.

It is the same with GPUs. A GPU can only speed up certain problems, and it would thus be even more inefficient to try and force every calculation through the GPU. You have libraries that only call the GPU when it is needed for certain calculations. This ends up offering major performance benefits and if the price of the GPU is low enough and the performance benefits high enough to match what the consumers want, they will buy it. We also have separate AI chips now as well which are making their way into some phones. While there’s no reason at the current moment to believe we will see quantum technology shrunk small and cheap enough to show up in consumer phones, if hypothetically that was the case, I don’t see why consumers wouldn’t want it.

I am sure clever software developers would figure out how to make use of them if they were available like that. They likely will not be available like that any time in the near future, if ever, but assuming they are, there would probably be a lot of interesting use cases for them that have not even been thought of yet. They will likely remain something largely used by businesses but in my view it will be mostly because of practical concerns. The benefits of them won’t outweigh the cost anytime soon.

Uh… one of those algorithms in your list is literally for speeding up linear algebra. Do you think just because it sounds technical it’s “businessy”? All modern technology is technical, that’s what technology is. It would be like someone saying, “GPUs would be useless to regular people because all they mainly do is speed up matrix multiplication. Who cares about that except for businesses?” Many of these algorithms here offer potential speedup for linear algebra operations. That is the basis of both graphics and AI. One of those algorithms is even for machine learning in that list. There are various algorithms for potentially speeding up matrix multiplication in the linear. It’s huge for regular consumers… assuming the technology could ever progress to come to regular consumers.

A person who would state they fully understand quantum mechanics is the last person i would trust to have any understanding of it.

I find this sentiment can lead to devolving into quantum woo and mysticism. If you think anyone trying to tell you quantum mechanics can be made sense of rationally must be wrong, then you implicitly are suggesting that quantum mechanics is something that cannot be made sense of, and thus it logically follows that people who are speaking in a way that does not make sense and have no expertise in the subject so they do not even claim to make sense are the more reliable sources.

It’s really a sentiment I am not a fan of. When we encounter difficult problems that seem mysterious to us, we should treat the mystery as an opportunity to learn. It is very enjoyable, in my view, to read all the different views people put forward to try and make sense of quantum mechanics, to understand it, and then to contemplate on what they have to offer. To me, the joy of a mystery is not to revel in the mystery, but to search for solutions for it, and I will say the academic literature is filled with pretty good accounts of QM these days. It’s been around for a century, a lot of ideas are very developed.

I also would not take the game Outer Wilds that seriously. It plays into the myth that quantum effects depend upon whether or not you are “looking,” which is simply not the case and largely a myth. You end up with very bizarre and misleading results from this, for example, in the part where you land on the quantum moon and have to look at the picture of it for it to not disappear because your vision is obscured by fog. This makes no sense in light of real physics because the fog is still part of the moon and your ship is still interacting with the fog, so there is no reason it should hop to somewhere else.

Now quantum science isn’t exactly philosophy, ive always been interested in philosophy but its by studying quantum mechanics, inspired by that game that i learned about the mechanic of emerging properties. I think on a video about the dual slit experiment.

The double-slit experiment is a great example of something often misunderstood as somehow evidence observation plays some fundamental role in quantum mechanics. Yes, if you observe the path the two particles take through the slits, the interference pattern disappears. Yet, you can also trivially prove in a few line of calculation that if the particle interacts with a single other particle when it passes through the two slits then it would also lead to a destruction of the interference effects.

You model this by computing what is called a density matrix for both the particle going through the two slits and the particle it interacts with, and then you do what is called a partial trace whereby you “trace out” the particle it interacts with giving you a reduced density matrix of only the particle that passes through the two slits, and you find as a result of interacting with another particle its coherence terms would reduce to zero, i.e. it would decohere and thus lose the ability to interfere with itself.

If a single particle interaction can do this, then it is not surprising it interacting with a whole measuring device can do this. It has nothing to do with humans looking at it.

At that point i did not yet know that emergence was already a known topic in philosophy just quantum science, because i still tried to avoid external influences but it really was the breakthrough I needed and i have gained many new insights from this knowledge since.

Eh, you should be reading books and papers in the literature if you are serious about this topic. I agree that a lot of philosophy out there is bad so sometimes external influences can be negative, but the solution to that shouldn’t be to entirely avoid reading anything at all, but to dig through the trash to find the hidden gems.

My views when it comes to philosophy are pretty fringe as most academics believe the human brain can transcend reality and I reject this notion, and I find most philosophy falls right into place if you reject this notion. However, because my views are a bit fringe, I do find most philosophical literature out there unhelpful, but I don’t entirely not engage with it. I have found plenty of philosophers and physicists who have significantly helped develop my views, such as Jocelyn Benoist, Carlo Rovelli, Francois-Igor Pris, and Alexander Bogdanov.

There 100% are…

If you choose to believe so, like I said I don’t really care. Is a quantum computer conscious? I think it’s a bit irrelevant whether or not they exist. I will concede they do for the sake of discussion.

Penrose thinks they’re responsible for consciousness.

Yeah, and as I said, Penrose was wrong, not because the measurement problem isn’t the cause for consciousness, but that there is no measurement problem nor a “hard problem.” Penrose plays on the same logical fallacies I pointed out to come to believe there are two problems where none actually exist and then, because both problems originate from the same logical fallacies. He then notices they are similar and thinks “solving” one is necessary for “solving” the other, when neither problems actually existed in the first place.

Because we also don’t know what makes anesthesia stop consciousness. And anesthesia stops consciousness and stops the quantum process.

You’d need to define what you mean more specifically about “consciousness” and “quantum process.” We don’t remember things that occur when we’re under anesthesia, so are we saying memory is consciousness?

Now, the math isn’t clean. I forget which way it leans, but I think it’s that consciousness kicks out a little before the quantum action is fully inhibited? It’s been a minute, and this shit isn’t simple.

Sure, it’s not simple, because the notion of “consciousness” as used in philosophy is a very vague and slippery word with hundreds of different meanings depending on the context, and this makes it seem “mysterious” as its meaning is slippery and can change from context to context, making it difficult to pin down what is even being talked about.

Yet, if you pin it down, if you are actually specific about what you mean, then you don’t run into any confusion. The “hard problem of consciousness” is not even a “problem” as a “problem” implies you want to solve it, and most philosophers who advocate for it like David Chalmers, well, advocate for it. They spend their whole career arguing in favor of its existence and then using it as a basis for their own dualistic philosophy. It is thus a hard axiom of consciousness and not a hard problem. I simply disagree with the axioms.

Penrose is an odd case because he accepts the axioms and then carries that same thinking into QM where the same contradiction re-emerges but actually thinks it is somehow solvable. What is a “measurement” if not an “observation,” and what is an “observation” if not an “experience”? The same “measurement problem” is just a reflection of the very same “hard problem” about the supposed “phenomenality” of experience and the explanatory gap between what we actually experience and what supposedly exists beyond it.

It’s the quantum wave function collapse that’s important.

Why should I believe there is a physical collapse? This requires you to, again, posit that there physically exists something that lies beyond all possibilities of us ever observing it (paralleling Kant’s “noumenon”) which suddenly transforms itself into something we can actually observe the moment we try to look at it (paralleling Kant’s “phenomenon”). This clearly introduces an explanatory gap as to how this process occurs, which is the basis of the measurement problem in the first place.

There is no reason to posit a physical “collapse” or even that there exists at all a realm of waves floating about in Hilbert space. These are unnecessary metaphysical assumptions that are purely philosophical and contribute nothing but confusion to an understanding of the mathematics of the theory. Again, just like Chalmers’ so-called “hard problem,” Penrose is inventing a problem to solve which we have no reason to believe is even a problem in the first place: nothing about quantum theory demands that you believe particles really turn into invisible waves in Hilbert space when you aren’t looking at them and suddenly turn back into visible particles in spacetime when you do look at them.

That’s entirely metaphysical and arbitrary to believe in.

There’s no spinning out where multiple things happen, there is only one thing. After wave collapse, is when you look in the box and see if the cats dead. In a sense it’s the literal “observer effect” happening our head. And that is probably what consciousness is.

There is only an “observer effect” if you believe the cat literally did turn into a wave and you perturbed that wave by looking at it and caused it to “collapse” like a house of cards. What did the cat see in its perspective? How did it feel for the cat to turn into a wave? The whole point of Schrodinger’s cat thought experiment was that Schrodinger was trying to argue against believing particles really turn into waves because then you’d have to believe unreasonable things like cats turning into waves.

All of this is entirely metaphysical, there is no observations that can confirm this interpretation. You can only justify the claim that cats literally turn into waves when you don’t look at them and there is a physical collapse of that wave when you do look at them on purely philosophical grounds. It is not demanded by the theory at all. You choose to believe it purely on philosophical grounds which then leads you to think there is some “problem” with the theory that needs to be “solved,” but it is purely metaphysical.

There is no actual contradiction between theory and evidence/observation, only contradiction between people’s metaphysical assumptions that they refuse to question for some reason and what they a priori think the theory should be, rather than just rethinking their assumptions.

That’s how science works. Most won’t know who Penrose is till he’s dead.

I’d hardly consider what Penrose is doing to be “science” at all. All these physical “theories of consciousness” that purport not to just be explaining intelligence or self-awareness or things like that, but more specifically claim to be solving Chalmers’ hard axiom of consciousness (that humans possess some immaterial invisible substance that is somehow attached to the brain but is not the brain itself), are all pseudoscience, because they are beginning with an unreasonable axiom which we have no scientific reason at all to take seriously and then trying to use science to “solve” it.

It is no different then claiming to use science to try and answer the question as to why humans have souls. Any “scientific” approach you use to try and answer that question is inherently pseudoscience because the axiomatic premise itself is flawed: it would be trying to solve a problem it never established is even a problem to be solved in the first place.

Roger Penrose is pretty much the only dude looking into consciousness from the perspective of a physicist

I would recommend reading the philosophers Jocelyn Benoist and Francois-Igor Pris who argue very convincingly that both the “hard problem of consciousness” and the “measurement problem” stem from the same logical fallacies of conflating subjectivity (or sometimes called phenomenality) with contextuality, and that both disappear when you make this distinction, and so neither are actually problems for physics to solve but are caused by fallacious reasoning in some of our a priori assumptions about the properties of reality.

Benoist’s book Toward a Contextual Realism and Pris’ book Contextual Realism and Quantum Mechanics both cover this really well. They are based in late Wittgensteinian philosophy, so maybe reading Saul Kripke’s Wittgenstein on Rules and Private Language is a good primer.

That’s the only way free will could exist…What would give humans free will would be the inherent randomness if the whole “quantum bubble collapse” was a fundamental part of consciousness.

Even if they discover quantum phenomena in the brain, all that would show is our brain is like a quantum computer. But nobody would argue quantum computers have free will, do they? People often like to conflate the determinism/free will debate with the debate over Laplacian determinism specifically, which should not be conflated, as randomness clearly has nothing to do with the question of free will.

If the state forced everyone into a job for life the moment they turned 18, but they chose that job using a quantum random number generator, would it be “free”? Obviously not. But we can also look at it in the reverse sense. If there was a God that knew every decision you were going to make, would that negate free will? Not necessarily. Just because something knows your decision ahead of time doesn’t necessarily mean you did not make that decision yourself.

The determinism/free will debate is ultimately about whether or not human decisions are reducible to the laws of physics or not. Even if there is quantum phenomena in the brain that plays a real role in decision making, our decisions would still be reducible to the laws of physics and thus determined by them. Quantum mechanics is still deterministic in the nomological sense of the word, meaning, determinism according to the laws of physics. It is just not deterministic in the absolute Laplacian sense of the word that says you can predict the future with certainty if you knew all properties of all systems in the present.

If the conditions are exactly the same down to an atomic level… You’ll get the same results every time

I think a distinction should be made between Laplacian determinism and fatalism (not sure if there’s a better word for the latter category). The difference here is that both claim there is only one future, but only the former claims the future is perfectly predictable from the states of things at present. So fatalism is less strict: even in quantum mechanics that is random, there is a single outcome that is “fated to be,” but you could never predict it ahead of time.

Unless you ascribe to the Many Worlds Interpretation, I think you kind of have to accept a fatalistic position in regards to quantum mechanics, mainly due not to quantum mechanics itself but special relativity. In special relativity, different observers see time passing at different rates. You can thus build a time machine that can take you into the future just by traveling really fast, near the speed of light, then turning around and coming back home.

The only way for this to even be possible for there to be different reference frames that see time pass differently is if the future already, in some sense, pre-exists. This is sometimes known as the “block universe” which suggests that the future, present, and past are all equally “real” in some sense. For the future to be real, then, there has to be an outcome of each of the quantum random events already “decided” so to speak. Quantum mechanics is nomologically deterministic in the sense that it does describe nature as reducible to the laws of physics, but not deterministic in the Laplacian sense that you can predict the future with certainty knowing even in principle. It is more comparable to fatalism, that there is a single outcome fated to be (that is, again, unless you ascribe to MWI), but it’s impossible to know ahead of time.