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Book Review: Quantum Processes, Schumacher & Westmoreland

November 30, 2020
Quantum Processes Systems, and InformationQuantum Processes Systems, and Information by Benjamin Schumacher
My rating: 4 of 5 stars

I have only been able to glance over various parts of this book so far. I came to it from the Science of Information lectures and from the same persons lectures on Quantum Mechanics. I find the whole information perspective on quantum theory fascinating and this book provides a rigorous introduction and overview of most of the key aspects and findings of this approach. Including the notions of Qubits, Ebits, the no Cloning Theorem, Bell’s Inequality, Quantum Teleportation, Error Correction Codes, Entanglement and the Use of Operators to conceptualise the transition from one quantum state to another. The middle sections also go into greater detail on quantum dynamical processes, but I did not currently read these, as the mathematics is not familiar to me yet.

The basic probability and information mathematics is relatively easy to pick up and similar to the ideas in the lectures series. But some of the operators, and notions such as Hermitian conjugates were a bit beyond my current level. A basic awareness of Linear Algebra gave me some access to the mathematics, but you also need good ability with complex numbers and some calculus to understand in better detail. It was a good challenge to read and understand as much as possible, and I will probably come back to it in future to explore some of the sections in more detail when I have a better mathematical grounding.

It would be really good to see a more popularised version of a lot of these ideas, to get across how valuable this perspective is for better understanding the quantum world and deflating a lot of what turn out to be misguided concerns about its supposed indeterminacy. On that front, one could argue here that the measurement problem is perhaps not addressed or under played in this approach, and there may still be some ontological questions to be asked about the significance of that. For instance, no attempt is made to address the Schrodingers Cat thought experiment from this information perspective that I have seen yet. And Roger Penrose, at least, and some others, seem to think this is an important objection to the physical consistency of quantum theory that suggest it may be incomplete or needs supplementing with a new more encompassing theory.

Overall, one can take this approach as seeing quantum theory as leading us to an understanding of just how fundamental the concept of information is to reality. The quantum goings on happen in black boxes that we cannot access, but we can understand them as input and output states just like in computing, and we can transition from one to the other, applying various linear algebraic operations upon the states. It leads to the suggestion that perhaps fundamentally there is no actual mechanical process going on in physical reality, only processes of information exchange. A famous phrase of this approach is that Quantum mechanics is what happens when no one is looking. But if it is the case that we cannot look at the quantum process in action, then is there really a mechanism involved at all at the quantum level, in the regular sense in which we understand that term?

Some others are not happy, and still search, perhaps in vain, like Einstein, for some mechanism that determines quantum systems. I guess time will tell, but this view for me makes the idea that there may never be a deterministic account of quantum theory a lot more palatable and acceptable.

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From → Philosophy, Writing

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