Quantum 2.0, page 1
Quantum 2.0
The Weird Physics Driving a New Revolution in Technology
Paul Davies
The University of Chicago Press
The University of Chicago Press, Chicago 60637
© 2025 by Paul Davies
All rights reserved. No part of this book may be used or reproduced in any manner for the purpose of training artificial intelligence technologies or systems. No part of this book may be used or reproduced in any manner whatsoever without written permission, except in the case of brief quotations in critical articles and reviews. For more information, contact the University of Chicago Press, 1427 E. 60th St., Chicago, IL 60637.
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Published 2026
Printed in the United States of America
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ISBN-13: 978-0-226-84932-4 (cloth)
ISBN-13: 978-0-226-84933-1 (ebook)
DOI: https://doi.org/10.7208/chicago/9780226849331.001.0001
First published in Great Britain in 2025 as Quantum 2.0: The Past, Present, and Future of Quantum Physics by Pelican Books, part of the Penguin Random House group of companies.
Library of Congress Control Number: 2025942259
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‘Anyone who is not shocked by quantum mechanics hasn’t understood it’
—Niels Bohr
Contents
PREFACE
PART ONE: PARADIGM SHIFT
CHAPTER 1
The Birth of the Quantum Concept
THE EQUATION THAT CHANGED THE WORLD
SIX UNEXPLAINED ODDITIES
THE FIRST QUANTUM LEAP
CHAPTER 2
Nature’s Lottery
WAVES OF WHAT?
BUT WHERE IS THE PARTICLE REALLY?
THE EXPERIMENTER AS CREATOR
WHAT HAPPENS TO A QUANTUM PARTICLE WHEN SOMEBODY LOOKS?
PASSING THROUGH WALLS
BLENDED ALTERNATIVE REALITIES
CHAPTER 3
What Lies Beneath
WAVE OR PARTICLE?
COMPLETING THE STORY
THE CAT PARADOX
QUANTUM TECHNOLOGY 1.0
CHAPTER 4
Reality Wars
EINSTEIN’S SPOOKY THOUGHT EXPERIMENT
BOX 1: POLARIZATION OF LIGHT
TANGLED REALITY
BOX 2: BELL’S BREAKFAST BAR
THE DEFINITIVE EXPERIMENT
HOW THICK IS A BRICK?
THE MAGIC SQUARE AND PSEUDO-TELEPATHY
THE GENESIS OF QUANTUM 2.0
BOX 3: A BLUFFER’S GUIDE TO QUANTUM PHYSICS
PART TWO: NEW TECHNOLOGICAL MARVELS
CHAPTER 5
Quantum Information Magic
FROM BITS TO QUBITS
DON’T TOUCH ANYTHING!
TELEPORTATION
QUANTUM CRYPTOGRAPHY
QUANTUM COMPUTERS: THE HOLY GRAIL OF QUANTUM INFORMATION SCIENCE
PRACTICAL CHALLENGES
QUANTUM CODEBREAKING
THE QUANTUM INTERNET
QUANTUM AI: MERGING TWO REVOLUTIONARY TECHNOLOGIES
BOX 4: QUANTUM MUSIC
CHAPTER 6
Sensing the Unseen
THE BEST CLOCK IN THE UNIVERSE?
QUANTUM RADAR
SENSING DARK MATTER
THE BIGGEST QUANTUM OBJECT IN THE WORLD
FINDING HIDDEN TREASURE
WHEN QUANTUM MEETS NANO
BOX 5: SPIN
FROM ELECTRONICS TO SPINTRONICS
QUANTUM NEUROSCIENCE AND OTHER MEDICAL MARVELS
WHAT NEXT?
CHAPTER 7
Quantum Biology
WHAT IS LIFE?
PHOTOSYNTHESIS: HARVESTING PHOTONS
BIRDS THAT CAN FIND THEIR WAY IN THE DARK
LIFE’S QUANTUM INTERNET
QUANTUM BRAINS
QUANTUM VITALISM?
PART THREE: COSMIC SPECULATIONS
CHAPTER 8
The Myth of the Void
MUCH ADO ABOUT NOTHING
CAN THE QUANTUM VACUUM BE DETECTED?
A FLASH IN THE DARK
DREAMS OF COSMIC ENGINEERING
VACUUM-POWERED SPACECRAFT?
HARNESSING THE QUANTUM VACUUM
WHOSE VACUUM IS IT ANYWAY?
CHAPTER 9
Universe Out of Nothing
QUANTUM ALL THE WAY UP?
QUANTUM FINGERPRINTS IN THE BIG BANG’S AFTERGLOW
THE RUNAWAY UNIVERSE
BLACK HOLES: WHAT GOES IN MUST COME OUT – OR NOT
PART FOUR: PHILOSOPHICAL FINALE: THE SEARCH FOR MEANING
CHAPTER 10
Weirder Still
THE DOG THAT DIDN’T BARK
BACKWARDS IN TIME? THE GHOSTS OF PHOTONS PAST
ERASING THE PAST
SNEAK PEEK: LIFTING THE VEIL ON QUANTUM UNCERTAINTY
CHESHIRE CATS AND OTHER OUT-OF-BODY EXPERIENCES
CHAPTER 11
Making Sense of It All
IS THE QUANTUM WORLD THE ULTIMATE REALITY?
WAYS IN WHICH QUANTUM MECHANICS MIGHT BREAK DOWN
NO BREAKDOWN: QUANTUM MECHANICS SHOULD BE ACCEPTED AS IT IS
BOX 6: PARALLEL UNIVERSES
CAN ANYONE GLIMPSE THE OTHER WORLDS?
OUR QUANTUM FUTURE
BIBLIOGRAPHY
ENDNOTES
ACKNOWLEDGEMENTS
INDEX
Preface
A hundred years ago, the world of science was upended by a theory so profound and so powerful that it has entered the popular lexicon: quantum. Within a few years of its formulation, quantum physics explained the nature of matter and forces across the universe, from subatomic particles to stars, resolving mysteries that had baffled scientists for decades. It has proven to be the most successful scientific theory in history, and underpins chemistry, particle physics, materials science, molecular biology and much of astronomy. It has penetrated every major industry, from mining to healthcare, and spawned several new ones. Its technological applications have shaped much of the modern world, and given us electronics, computers, AI, the internet, global communications, precision navigation, nanotechnology, LEDs, high-definition TV screens and smartphones. Lasers, transistors, superconductors and microchips are all products of the quantum age. It is no exaggeration to say that the quantum revolution, which began in earnest in 1925, was the most disruptive technological transformation in history.
But what makes quantum theory of such immediate importance over a century after its inception is that a second great quantum revolution is now underway, one that promises to rival the first in its far-reaching scientific, industrial and social ramifications. Dubbed Quantum 2.0, it is known more formally as quantum information science. It arises from the ability of scientists and engineers to control individual atoms, electrons and photons, and to process, store and transmit information in novel and previously unimagined ways. This emerging technology has led to totally unbreakable encryption protocols, sensors and scanners of unprecedented power and feats like teleportation that seem little short of magic. Above all, quantum information science holds the tantalizing promise of a completely new concept in technology – the quantum computer – that will far outperform the world’s best conventional supercomputers. A fully functional quantum computer will possess unrivalled capabilities for genetic analysis, drug design, climate modelling, market analysis and the fabrication of smart materials. But the most disruptive application of a quantum computer is its ability to break the codes in widespread use for secure data encryption, a looming threat that has been dubbed the quantum apocalypse. At this time, the world is in thrall of the disruptive effects of AI. But the science that gave us AI – quantum physics – looks set to merge with it in the near future, enormously enhancing its power and scope. The impact of QAI – Quantum Artificial Intelligence – is almost impossible to predict. Just as Quantum 1.0 drove the information age that defined much of the twentieth century, so Quantum 2.0, of which QAI represents but one component, will shape the twenty-first century, likely in ways that we cannot yet imagine.
Given the promise of quantum information science, it is no surprise it is attracting the attention of governments and businesses worldwide. The UK has established a National Quantum Technologies Programme, explaining that, ‘Our lives and economies will soon be transformed by quantum technologies as profoundly as they have been by steam, electric traction, radio communications and electronics.’1 The US government passed the Quantum Initiatives Act in 2018, while President Xi Jinping has called for ‘a great leap forward’ in quantum technologies. Other countries have followed suit.2 UNESCO has declared 2025 to be the International Year of Quantum Science and Technology. Companies too are scrambling to exploit second-generation quantum technology in the financial, mining, healthcare, energy and aerospace industries, with applications across most sectors of the economy. In their third annual Quantum Technology Monitor, the investment firm McKinsey assess that quantum technology could create market value worth trillions of dollars within the next decade.3
With opportunities inevitably come threats. In 1994, it was discovered that a quantum computer could be programmed to crack ma ny of the world’s standard encryption codes used to protect financial transactions and confidential information exchange. What emerged was a new arms race, especially between China and the West, to develop quantum computers first. Big tech firms soon piled in and are currently leapfrogging each other to attain ‘quantum supremacy’. Quantum sensor technology is also advancing in leaps and bounds. It is making conventional military detection and navigation systems obsolete, and raising the stakes for smart surveillance of submarines, missiles and stealth bombers. With quantum sensing, today’s lurking menace could be tomorrow’s sitting duck. Combining quantum target detection with AI threatens to completely disrupt the global strategic landscape. And, while quantum sensors are proving a boon to medical science, projects that use quantum neuroimaging to couple brains to computers have triggered unsettling ethical concerns. As with all disruptive technologies in their infancy, the downstream consequences are hard to predict, but it is safe to say that whoever controls Quantum 2.0 controls the world.
It may then come as a shock to learn that, for all its momentous impact on our lives and well-being, quantum physics stems from a theory that, to put it bluntly, makes no sense. That theory – called quantum mechanics – works brilliantly, but it implies that the atoms, molecules, electrons and photons that are so profitably manipulated by scientists and engineers do not actually have a definite independent existence. The concrete world of daily experience dissolves away at the atomic level into a blurry amalgam of blended realities, resolved only by the intervention of some form of specific measurement. Common sense and intuition fail completely when we try to grasp what is ‘really going on’ in the quantum domain. On its inception in the 1920s, quantum mechanics proved so troubling that some of the world’s leading physicists, most notably Einstein, flatly rejected its implications of fuzzy reality and laboured to discredit the theory in its accepted form. To do this, they zeroed in on a prediction of the theory so weird – so ‘spooky’, in Einstein’s words – that it seemed to be self-evidently absurd: namely, that particles on opposite sides of the lab, or even the galaxy, are entangled by a sort of telepathic tether in a way that has no counterpart in normal life. It took until the 1980s for an experiment to be performed to test the prediction, and to the consternation of the sceptics, it demonstrated that nature is just as spooky as Einstein feared.
What followed was remarkable. It dawned on physicists that this long-range ‘entanglement’ could be embraced and used as a resource to drive a new technological era – what matured into today’s quantum information science. Rather than sweeping the weirdness under the carpet, as was done for decades, scientists and engineers took it at face value and began leveraging it for practical applications.
The successes of this approach notwithstanding, merely accepting the intrinsic ambiguity of quantum reality hasn’t solved the fundamental problem, which is this: how does the focused reality of the everyday material world emerge from the blurred amalgam of its microscopic constituents? The quest to understand what, precisely, it means to know something about a quantum particle remains an outstanding challenge. There are many contending interpretations of quantum mechanics, some of them invoking parallel universes or mental as well as physical states. These philosophical deliberations have been accompanied by a flurry of additional experimental tests suggesting that the quantum world is even weirder than we thought.
My aim in writing this book is to explain in basic terms what quantum mechanics is and how it works, tracing it back to its origins in early twentieth-century physics. I will outline its stunning technological implications and carefully discuss what it says – and doesn’t say – about the deep nature of reality. In this endeavour I am hampered by the number one rule of science popularization: no mathematics allowed! Many of the weird aspects of the quantum world cannot be properly described in everyday language, only in equations and symbols. I have done my best using analogies and informal descriptions, but that inevitably risks creating misunderstandings. Since quantum mechanics remains a work in progress, with sharp disagreements among professionals about interpretational aspects, the reader should be cautioned that I have put my own slant on the subject. I have included a Bibliography for those who wish to explore alternative approaches and ideas.
PART ONE
Paradigm Shift
CHAPTER 1
The Birth of the Quantum Concept
Suppose that the everyday world we experience through our senses is but a tiny, impoverished fragment of a stupendously greater realm, one that is incomparably rich, exuberantly dynamic and bewilderingly alien. Envisage a domain of boundless possibilities, of subtle convolutions of form and substance, distributed all around us and inside us, flowing out into infinite dimensions beyond our ken and even beyond the reach of our imagination. That dazzling, gargantuan domain is in fact the world in which we are already inescapably embedded, but from which we are almost totally shut out. Access to this alien world is attained only through infinitesimal portals, observational pinholes that afford but momentary glimpses of a seething wonderland of restless activity, vaster than all the universe we see, vaster even than all possible universes we can comprehend, vaster indeed than all conceivable vastness.
Welcome to the quantum universe.
And immediately we hit a foundational question: is this magical metaverse merely an abstraction, a mathematical frolic of interest only to physicists and philosophers, or does it in some sense really exist? That question – what is real? – goes right to the heart of the quantum story, and indeed of the entire scientific enterprise.
To ease ourselves into this weighty topic, let’s start with a brief anecdote. When I was fifteen, my sister’s boyfriend saw a ghost. At least, that’s what he claimed, having spent the night sleeping downstairs in our living room, which we children long believed was haunted. My mother was sceptical, however. ‘He was probably just dreaming,’ was her opinion, ‘or drunk.’ I preferred the ghost story. Who was right? Was there ‘really’ a ghost in our living room or was the whole affair just a figment of the young man’s imagination?
Each of us experiences a world ‘out there’, which we view through our eyes and interpret via the information-processing taking place in our brains. Reality, for any one of us, is a product of the external and internal, of matter and mind. To get around this, a long list of philosophers, from Aristotle and René Descartes to John Locke and Thomas Nagel, defended the notion of objective reality – a physical universe that exists independently of our individual observations, and which has done so since long before human observers appeared on the scene. It is a world made of material objects that move and change in response to various forces. That, at least, is the normal view of existence adopted by Western thought. And yet, as I shall explain, quantum mechanics confounds this simplistic version of an objective, independent reality. There is indeed a world ‘out there’, but it is far stranger than most people imagine, or, in fact, can imagine.
Reality is a slippery concept, about which entire volumes have been penned by eminent thinkers over the centuries. Most of us, however, make do with a rough-and-ready notion that goes something like this: if an entity is real, then its existence could, in principle, be confirmed by someone else. It should be ‘independently verifiable by a disinterested investigator’, to put it formally. It’s a sentiment well encapsulated in the motto of Britain’s national scientific academy, the Royal Society: Nullius in verba – Take nobody’s word for it. For the two and a half centuries after the Society’s founding in 1660, that pragmatic assumption accorded with the common-sense view that there are definite facts about the world, whether or not anybody is checking. Thus, science took as its basis objective truth, as opposed to personal subjective experience that might include dreaming, hallucination, hypnotic suggestion, mirages and, well, ghosts. It therefore came as a bombshell to scientists when, early in the twentieth century, a new theory emerged, which shattered this comforting belief by implying that the external world lacks definite objective existence when it isn’t being watched.
The equation that changed the world
On 27 January 1926, the world changed forever. It was on that day that the German scientific journal Annalen der Physik published a paper by the Austrian physicist Erwin Schrödinger (see Fig. 1) which demolished centuries of belief about the nature of matter and the way the physical world is put together. It had been apparent for a quarter of a century that something was very wrong with the traditional concept of material objects on the atomic and molecular scale, but it took the publication of a specific equation – Schrödinger’s equation – to sweep away the old picture of matter and open the path to an entirely new way of thinking about the physical universe. What emerged, following a few years of frenzied analysis by the world’s leading physicists, was the birth of an entirely new scientific discipline called quantum mechanics. It transformed our understanding of reality, reshaped the landscape of science, and gave birth to entire new industries that have powered economic growth for decades.
