Book Review: A Shortcut Through Time

Book Review: A Shortcut Through Time: The Path to the Quantum Computer by George Johnson

One of my favorite parts of this book was the preface “Inside the Black Box” where the author Johnson talks about why he writes books like this. He’s an armchair scientist, not interested in every detail of how something works, but more the general concept. It was in that spirit that I was interested in quantum computers. I was specifically wondering how they would be able to break encryption algorithms that currently would take a modern computer 100s of years. A 64 atom (well quanta) quantum computer would have more processing power than a super computer that covered every square inch of this planet. This is what I wanted to understand.

I’ve read numerous books on quantum physics and taken many classes on the subject and yet I still believe that humans are incapable of understanding, on a deep level, quantum mechanics. Specifically the spin, or quantum leap: the ability for an object to have two positions, or be spinning in both directions, at the same time.

Johnson briefly tries to explain this, using some classic examples, but, in the end, just states that you need to accept this as fact.

He does a nice job of explaining how modern computers actually work. He goes into depth of how turning machines work (which is what the British used to break the Enigma machine during WWII) and explains how to build a computer to play tic-tac-toe out of Tinker Toys (a classic MIT project).

For a few chapters he detours into math theorems on primes and basic logic as a lead in to some of the earliest proof-of-concept quantum computers built.

Finally he gets around to the how and why of quantum computing. In an over simplification on my part, I guess I came away thinking that, the way quantum computers work, is by exploiting the dual spin properties of a quantum particles. Basically, you chain quanta together (setup simple rules like “if quanta 1 = spin-right then quanta 2 = spin left – this is where you get the classic binary 0/1 of computers from). You then put the how thing in super position (where the quanta are spinning left and right, at the same time) and viola, out comes an answer. With a classic computer you’d have to try each path. The quantum computer tries all paths at the same time.

So, in typical quantum fashion, I feel like I can explain how a quantum computer works but I don’t feel I have a deeper understanding of them, because they’re just too bizarre. The people working on this stuff must not be human. :)

Anyway – great book. Really interesting and simple examples of how computers actually work. Some interesting thoughts on what quantum computing will mean to us (we’ll finally be able to figure out protein factories – which is what will make genetics really interesting). It’s a fun, fast read, I’d highly recommend it.

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