The Quantum Enigma
“I think I can safely say that nobody really understands quantum mechanics,” said Richard Feynman in 1964. One year before he got the Nobel prize for his work in quantum mechanics.
What was he referring to and do we still not understand it?
Let’s briefly explore the key ideas of quantum mechanics to set the context and the language for diving deeper.
In quantum mechanics, we need two kinds of information to describe the fundamental particles that make up our universe:
- Fundamental properties: Intrinsic characteristics that do not change with time – mass, charge, etc.
- Quantum states: Characteristics of the particle that change with time – position, momentum, etc.
Whenever we interact with a particle in the real world, we always find it in a definite and singular quantum state. This is important to state since there is a lot of confusion about this on the internet.
However, if we want to predict which of the many possible states it will be in, we find it impossible to do so with 100% accuracy. The equations of quantum mechanics can only tell us the probability of finding it in each possible state.
This isn’t strange. There are examples like this even in classical physics. If we want to predict a coin toss before it lands, the best we can do is calculate the probability of getting heads and tails – 50% each.
However, in classical mechanics, this uncertainty comes from not knowing all the information required to predict a coin toss. If we know all the information, it is possible to predict the outcome of a coin toss with 100% accuracy.
This is not the case in quantum mechanics.
In quantum mechanics, we use a mathematical quantity called wave function to calculate the probability of finding a particle in one state or another. Most of our difficulty in understanding quantum mechanics comes from not knowing how to interpret what this wave function means.
But what’s the big difficulty? Why don’t we interpret it the same way as we interpret probability in classical mechanics?
Because some experiments, like the famous double-slit experiment, showed us that different possible states of a particle can interact with each other to change how the particle behaves. In the case of a coin toss, it’s like the “possibility of heads” interacting with the “possibility of tails”, to give you new answers for the probability of getting heads or tails when the coin lands.
But wait, you might say, it’s just a mathematical possibility, not two separate real coins – one head, one tail – how will they interact with each other?
That’s the puzzle.
Almost all the strangeness of quantum mechanics comes from this interaction between “mathematical possibilities” that are not even supposed to be real in classical mechanics.
Why and how do they interact? Does this mean all mathematical possibilities are real in some sense or some other universe?
If they are real, why don’t other limitations that apply to real things apply to them? Like the limitation Einstein discovered – “no information can travel faster than the speed of light between two real particles” which is broken when entangled particles instantly exchange information even if they are light years away.
If they are neither real nor purely mathematical, are they something in between?
I can summarize the answer to all these questions by borrowing Feynman’s words from 1964 – “I think I can safely say that nobody really understands.”
Enter QBism
For the longest time, I struggled to find a clear enough articulation of what QBism says. Eventually, as I understood it better, I came up with one:
QBism argues that a wave function represents the real information we have, as observers, about various possible states of a particle.
To truly understand QBism, we must remind ourselves that no particle (or person) ever finds any other particle in a superposition of multiple possible states in the real world. It only happens in the “mathematical model” we must construct to predict what we may observe in the real world. It’s as if they exist in a superposition of multiple states before we interact with them. As-if.
Most particles in the universe do not go around predicting each other. As far as they are concerned, there’s no strangeness or spookiness in our universe. Every particle always exists in definite and singular states whenever they observe each other.
The only entities that encounter spookiness are the ones trying to predict future outcomes – like us. To do this, they must store and manipulate information somewhere – brains, computers, something else – making it real.
If quantum mechanics describes this real information about particles and NOT the particles themselves, then all the spookiness disappears!
Superposition? Of course, our information about a particle can exist in a superposition of two states. The contradiction disappears.
Faster-than-light communication between entangled particles? No matter how far two particles travel, our information about them remains within us. So, there’s no need for faster-than-light communication to update our information about the two entangled particles. Contradiction disappears.
All we have to give up in exchange is our belief that physics describes objective reality, not just our information about it.
Not Again!
“Not again! 🙄” This is probably what you’re thinking if you’ve read my previous article about Predictive Processing – an emerging view of our brain as a prediction machine that perceives its own predictions as reality.
Well, what can I say? I am obsessed with ideas that question the very nature of reality we perceive (neuroscience) or live in (physics).
If we look at history, every time science seemed stuck and unable to progress, it was eventually set free by ideas that questioned and altered our understanding of the very nature of reality. Why should it be different this time around?
As always, I hope this post sparks enough excitement in you to explore this beautiful idea on your own. And if you ever need another curious mind to give you company on this journey – hit me up! ✨
