Book Review: The Feynman Processor — Quantum Entanglement and the Computing Revolution

ByGeorges Lteif

I. About the Book

Title

The Feynman Processor — Quantum Entanglement and the Computing Revolution

Author

Gerard J. Milburn

First Published

1998

Edition

First

Pages

213

II. Who Should Read “The Feynman Processor”?

“The Feynman Processor” is neither about Richard Feynman’s contributions to quantum computing nor about processors (or computing as represented in computer science). It is rather about the fundamental principles that make quantum computing possible. In this book, Milburn introduces quantum computing to the lay audience.

Although quantum computing might seem like a synthesis of two fields (quantum mechanics and theory of computation), the distance between quantum computing and these two pillars is substantial, making the topic challenging to explain in a short book. However, Milburn has done a brilliant job in concisely covering the essential topics of quantum mechanics (quantum uncertainty, interference, and randomness) and how these can be used to build a conceptual model of a new type of computer, one that allows simultaneous calculations to be done in great numbers.

With training in electrical engineering, a career in software, and a lifetime of reading popular science books, I found the “The Feynman Processor” beautiful and hard to read. I had to read all the essential sections twice (at least) before they indeed sunk in.

If you are passionate about quantum computing and reasonably comfortable with the essentials of quantum mechanics, theory of computation, and Turing machines, “The Feynman Processor” should be a joyful ride.

III. “The Feynman Processor” Synopsis

The book is divided into six chapters, as follows:

  • Chapter 1: The Quantum Principle — Inexhaustible Uncertainty
  • Chapter One discusses quantum uncertainty and how radically different it is from our classical understanding of chance and probability, embodied in Laplace’s and Bayes’ rules.
  • The chapter also explores the path of photons through beam splitters in great detail, explaining important concepts such as quantum interference, probability amplitudes, and Feynman’s rule for amplitude addition.
  • This chapter, however, does not explain interference as it was described in either QED or The Character of Physical Law. If you are interested in the physics, these two books will be ideal.
  • Chapter 2: Quantum Entanglement
  • Chapter Two is an exhaustive discussion of quantum entanglement that will not leave the reader perplexed or wanting more.
  • Milburn provides at least a couple of examples of the classical correlation between two attributes of a system before showing how similar results cannot be achieved with entangled quantum particles.
  • This chapter also explores the significance of the hidden variable theory behind the Einstein-Podolsky-Rosenburg (EPR). It shows why hidden variables cannot account for what is observed in quantum entangled systems.
  • Chapter 3: Teleportation for Gamblers
  • Chapter Three explores quantum entanglement further. This time, three entangled particles are examined, and the Greenberger-Horne-Zeilenger (GHZ) experiment is analyzed in great detail.
  • This chapter also extensively explores the properties of two entangled particles separated by large distances. Compared to others, this story’s originality is that a third particle is involved. The results of the measurements on particle A are impressed on those at B, as you would expect from entangled systems.
  • Chapter 4: Reality, by Nintendo
  • In the first half of chapter four, Milburn discusses Turing machines and the theory of computation. In the other half, he discusses David Deutsch’s Church-Turing Principle, which he stated in his 1985 paper on quantum computers.
  • The ideas presented in this chapter are fascinating. They revolve around quantum computers’ ability to simulate nature, particularly quantum mechanics. The argument is that only quantum computers can simulate quantum mechanics.
  • Chapter 5: Quantum Software
  • In this chapter, Milburn explores quantum circuits and algorithms. He discusses Hadamard gates and Controlled Not gates in great detail.
  • The author then presents Deutsch’s algorithm (the oracle) before explaining Shor’s integer factorisation algorithm.
  • Chapter 6: The Dream Machine
  • The closing chapter reviews the technical problems quantum computer engineers face, mainly error correction due to quantum decoherence.

Central Themes of “The Feynman Processor”

  • Quantum randomness
  • Quantum interference
  • Quantum logic circuits
  • Quantum circuits and algorithms
  • Quantum computers
  • Shor’s algorithm for integer factorisation
  • Universal quantum machines

IV. What I Liked About “The Feynman Processor”

  • Coverage
  • The book covers quantum computing as you would expect, starting with quantum mechanics and the theory of computation before building the quantum computer model.
  • Writing Style
  • The author has taken great pains to explain complex topics from multiple angles and with numerous examples.
  • The writing style alternates between narrative and semi-academic.
  • Depth
  • The author dedicated half the book to quantum interference and entanglement, prerequisites for understanding quantum computing. The depth with which these topics were discussed matched my expectations about the book.
  • The book’s second half, dedicated to quantum computers and algorithms, also had sufficient depth, given that it’s a popular science book.
  • Conciseness
  • The book is relatively short, at 213 pages. It is very light on history or irrelevant material, focusing straight on the topic.

V. What Could Have Been Better in “The Feynman Processor”

  • Accessibility
  • Quantum computing is a non-intuitive, challenging topic, and you wouldn’t expect any discussion on it to be straightforward. Through no fault of the author, some passages had to be read twice and thrice before finally grasping the idea.
  • The book could have used more diagrams, pictures, and maybe equations to keep the reader firmly anchored on the present discussion. Instead, the reader must always hold a complex sequence of thoughts in his mind.
  • Clarity
  • It seemed the author tried too hard to convey the ideas, sometimes repeating key phrases multiple times and explaining facts that should have been fairly obvious in fewer words.

VI. Final Verdict

“The Feynman Processor” is an excellent introduction to quantum computing. Even if you don’t get much of the quantum computing part, the book’s first half, dedicated to quantum mechanics topics relevant to quantum computing, was a delight to read.

Overall, the book is highly recommended for anyone interested in the topic with some quantum mechanics background.

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