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Einstein and the Quantum Revolutions

With a Foreword by David Kaiser
Translated by Teresa Lavender Fagan

A Nobel laureate offers a brief lesson on physics’ biggest mystery, accessibly explaining the two quantum revolutions that changed our understanding of reality.
 
At the start of the twentieth century, the first quantum revolution upset our vision of the world. New physics offered surprising realities, such as wave-particle duality, and led to major inventions: the transistor, the laser, and today’s computers. Less known is the second quantum revolution, arguably initiated in 1935 during a debate between giants Albert Einstein and Niels Bohr. This revolution is still unfolding. Its revolutionaries—including the author of this short accessible book, Nobel Prize–winning physicist Alain Aspect—explore the notion of entangled particles, able to interact at seemingly impossible distances. Aspect’s research has helped to show how entanglement may both upend existing technologies, like cryptography, and usher in entirely new ones, like quantum computing. Explaining this physics of the future, this work tells a story of how philosophical debates can shape new realities.

112 pages | 7 halftones | 5 x 8 | © 2024

The France Chicago Collection

Physical Sciences: Physics--Popular Books

Reviews

“[A] beautifully produced little book. . . . The book’s brevity and clear writing . . . make for an interesting overview of quan­tum ideas and their history. . . . Slim but not slight. . . . The stories here are beguiling.”

Robyn Arianrhod | Australian Book Review

"The French Nobel laureate Aspect explains there has been not just one quantum revolution but two. The second is ongoing, with the results being felt in areas such as computing and communications. This, says Aspect, is the science of the future; the full potential of 'entangled particles' which interact at distance is still unfolding."

New Statesman

"French physicist Aspect is a pioneer in ‘quantum entanglement’—connections between the quantum properties of subatomic particles that are preserved even at distances too great for signals to travel at light speed. He shared the 2022 Nobel Prize in Physics for this work, which underpins quantum computers and other technologies. With his book on the foundations of quantum mechanics being released, Aspect . . . [tells] why he sees parallels between physics and magic, why Einstein doesn’t get all the credit he deserves and how there were two quantum revolutions, not one."

Ron Cowen | Nature

"Nobel Prize–winning physicist Aspect offers a brisk . . . overview of how Albert Einstein set off two twentieth-century upheavals in physics. In 1909, Einstein resolved scientific debate over the nature of light by proposing it 'was both a particle and a wave,' Aspect explains, noting that the discovery underpinned the development of computers and 'lasers that enable the processing and transmission of information' through optical fibers. The second revolution followed Einstein’s 1935 postulation that, according to quantum mechanics, there are circumstances under which two subatomic particles can be 'entangled' and act on each other regardless of the distance separating them. Aspect recounts how this idea remained the purview of abstract philosophical inquiry until the 1970s, when he and other physicists began developing techniques to work with entangled photons and paved the way for research that promises to produce quantum computers capable of performing calculations in a fraction of the time current computers require. Aspect does a solid job of covering how Einstein’s innovations have changed the world. . . . This intrigues."

Publishers Weekly

"Aspect's work was fundamental to showing that quantum theory really did do away with local reality—that entangled quantum particles were genuinely able to effectively communicate (even though we can't control what they communicate) instantaneously at any distance. . . . For entanglement groupies like me, anything about the subject is worth having, and I'm glad to be able to read (translated from the French by Fagan) some words from the great man."

Brian Glegg | popularscience.co.uk

"It is nice to have a description of this very topical subject in the (translated) words of one of the main players in the field. . . . An easily digestible summary of the topic, in keeping with Einstein’s dictum to make everything as simple as possible but not simpler."

The Observatory

“Fascinating. . . . Aspect’s beautiful experiment, completed in 1982, had a catalyzing effect on the scientific community. . . . The tiny spark of the second quantum revolution began to grow.”

David Kaiser, author of "Quantum Legacies," from the foreword

“Lively, accessible, and brisk, Aspect’s book tells a compelling century-long story of groundbreaking discoveries. This is the perfect introduction to turn any reader into a quantum physics enthusiast.”

Florian Carle, manager of the Yale Quantum Institute

“This book tells a magnificent story of science, in which experimentation made it possible to resolve philosophical debates.”

Pour la Science (France), on the French-language edition

“Simple and excellent.”

L’affranchi de Chaumont (France), on the French-language edition

“A slim book that authoritatively outlines the foundations and paradoxical consequences [of quantum mechanics].”

Piero Bianucci | La Stampa (Italy), on the Italian-language edition

“Retraces one of the liveliest scientific debates of the last century.”

Almanacco della Scienza (Italy), on the Italian-language edition

"This book is a journey between theory and experiment, between mathematical models and reality, between science and technology."

Massimo Inguscio, president emeritus of the Consiglio Nazionale delle Ricerche, Italy, from the foreword to the Italian-language edition

Table of Contents

Foreword by David Kaiser

Two Quantum Revolutions
The First Quantum Revolution
Wave-Particle Duality
The Success of the First Quantum Revolution
The Second Quantum Revolution
Entanglement Measurement Experiments
The Manipulation of Quantum Objects
Quantum Information
Quantum Cryptography
In Search of the Limit

About the Author

Excerpt

What is a difficult problem? For a computer scientist or a mathematician working in this field, a difficult problem is one that requires a calculation time that increases exponentially with the size of the object under consideration. For example, internet security uses a coding called RSA, after Ron Rivest, Adi Shamir, and Leonard Adleman, who described the algorithm in 1977. RSA security is based on the impossibility of factoring a sufficiently large number into prime factors. Factoring into prime factors means, for example, breaking down the number 60 into 3 multiplied by 4 multiplied by 5. Factoring a large number takes considerable time because you have to try all the prime numbers less than the square root of the number.

This calculation difficulty is the foundation of security. A few years ago, on the internet, coding was done on 64-bit numbers. But, with today’s more powerful computers, with great effort and networking, we can crack the code. The number of bits is then doubled, going to 128 bits, and we can rest easy for ten years. Going to 256, we enjoy another ten years, and so on. A number of theoretical physicists, applied mathematicians, and theoretical computer scientists have discovered that certain difficult problems, such as the one just described, would become easier to solve if there were a quantum computer. For example, what is called Shor’s algorithm, after mathematician Peter Shor, would enable the factorization of a number in a time that would no longer increase exponentially with size, but in a more reasonable way: a polynomial increase.

To implement Shor’s algorithm, one would need a perfect quantum computer. What does that entail? It would use quantum bits, qubits, entangled with each other. To give a vague idea of what this means, we must first ask ourselves what an ordinary “bit” is. In a classical computer system, a bit is a value that can be either 1 or 0, but never both. One traditional way to think of the two states is as a light switch, on or off. But we might equally think of the states as a photon which can go either to one side of the beam splitter or to the other.

In the quantum world, a bit can also be 1 or 0. But here is the interesting part: it can also at the same time be 1 and 0, like the photon that goes to both sides of the beam splitter at the same time in the interference experiment. So, a quantum bit or “qubit” is one that can be put in a state that is a superposition of 1 or 0. If we now take two quantum bits and entangle them, we have access to a great wealth of states because we can have 0–0, 0–1, 1–0, and 1–1, and all the combinations of these four possibilities. If we take three qubits, we have eight basic possibilities (0–0–0, 0–0–1, and so on) as well as the combinations of all those possibilities. If we entangle ten quantum bits, we obtain about a thousand basic possibilities. With twenty, we get one million basic possibilities . . . That’s exponential growth!

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