Abstract Chapter 1, ‘Before the Quantum’, outlines the key ideas of the book. After a brief introduction to pilot-wave theory, we highlight its nonlocality—the ‘spooky’ action at a distance between widely separated systems. We then introduce the ‘conspiracy’ of why nonlocality cannot be controlled for practical superluminal signalling. To explain it, we draw an analogy with the classical ‘heat death’ of the universe theorised in the nineteenth century. The conspiracy can be understood as a peculiarity of the state of ‘quantum death’ in which we happen to live, where all systems are subject to the same quantum noise or uncertainty. We explain how this state arose from a past process of quantum relaxation (analogous to thermal relaxation). Finally, we outline three possible ways to escape quantum death, and thereby to access the wider physics beyond quantum mechanics.
Abstract Chapter 1, ‘Before the Quantum’, outlines the key ideas of the book. After a brief introduction to pilot-wave theory, we highlight its nonlocality—the ‘spooky’ action at a distance between widely separated systems. We then introduce the ‘conspiracy’ of why nonlocality cannot be controlled for practical superluminal signalling. To explain it, we draw an analogy with the classical ‘heat death’ of the universe theorised in the nineteenth century. The conspiracy can be understood as a peculiarity of the state of ‘quantum death’ in which we happen to live, where all systems are subject to the same quantum noise or uncertainty. We explain how this state arose from a past process of quantum relaxation (analogous to thermal relaxation). Finally, we outline three possible ways to escape quantum death, and thereby to access the wider physics beyond quantum mechanics.
Abstract ‘Beyond Quantum Physics’ delves into some detail about the new physics that could be accessed if ever we were able to escape from the restrictive state of quantum death. We begin with a deeper discussion of the ‘quantum conspiracy’, which prevents us from using nonlocality for signalling. We explain precisely why the conspiracy is a peculiarity of the state of quantum death as described by Born’s formula, and we show how superluminal signalling inevitably arises in more general ‘nonequilibrium’ conditions. We also give more details about how quantum relaxation to Born’s formula takes place. The chapter ends with a discussion of other properties of ‘subquantum matter’ (matter breaking Born’s formula), in particular how it could be deployed to circumvent the uncertainty principle.
Abstract ‘Seeing the Impossible’ delves into the details of pilot-wave theory and of how it can account for the mysteries of quantum physics. We begin with the iconic two-slit experiment and show how it can be understood in terms of particles moving through one hole or the other (despite widespread claims to the contrary). We give a clear explanation for so-called quantum randomness in terms of unknown ‘initial conditions’. We also show how Born’s usual formula, for quantum probability, can emerge from the peculiar particle motions predicted by the laws of pilot-wave theory. The chapter ends with a detailed discussion of how pilot-wave theory explains nonlocality, or spooky action at a distance, between widely separated particles.
Abstract Beyond the Quantum offers a panoramic rethink of quantum physics, with potentially revolutionary implications for cosmology, quantum gravity, and quantum technology. Properly understood, ‘pilot-wave theory’ provides a deeper foundation for quantum mechanics, while also going beyond it. First proposed in the 1920s by French aristocrat and physicist Louis de Broglie, and revived in the 1950s by American physicist David Bohm, the theory posits hidden particle motions we cannot currently see or control. The theory is usually regarded as merely an alternative account of the same physics we already know. In fact, pilot-wave theory implies a wealth of new and radical physics beyond the reach of quantum mechanics. Pilot-wave theory tells us that quantum physics is a special case of something broader and deeper. In more general ‘nonequilibrium’ conditions, Einstein’s relativity and Heisenberg’s uncertainty break down. Superluminal signalling becomes possible, and quantum particles can be clearly seen and controlled. This new physics could have left traces in the early universe, and it might be visible today in radiation from exploding primordial black holes. Harnessing this new physics would have transformative technological implications, in particular for communication, cryptography, and computing. Drawing intriguing parallels between the present era of quantum physics and past episodes of scientific confusion, this book tells the story of how pilot-wave theory was discovered and abandoned, revived and reconstructed, and how today it can pave the way to a new and radical physics beyond the quantum.
Abstract The Prologue provides historical perspective and motivation for the book, as well as a preview of its contents. We note the recurring philosophical conflict between ‘perception’ and ‘reality’ down the ages, drawing historical parallels with the Copernican revolution in astronomy and with the rise of atomic theory in thermodynamics. We explain why reality inevitably wins out over perception, despite the perennial scepticism. We show how the notoriously confused theory of quantum physics can be clarified by admitting a reality behind the scenes, that lies beyond our present perceptions. The Prologue ends with an outline of pilot-wave theory and of the main conclusions of the book.
Abstract So, where do we go from here? It is apparent from the last two chapters that nature denies us the easy way out. The clear experimental demonstration of quantum entanglement rules out the idea of local hidden variables, one of the simpler solutions to the conceptual problems of quantum theory. For the time being at least, we are forced to live with the consequences of entanglement, non-locality, and ‘spooky’ action at a distance. This might make some of us uncomfortable, but there is no solace in the Copenhagen interpretation, which does not provide us with any answers and is still regarded by many to be no interpretation at all. And, lest we forget, there remain the problems of interpreting the meaning of quantum probability and the collapse of the wave function. Even those who adhere to the Copenhagen view tend to put aside or disregard the conceptual difficulties that these issues raise as they analyse the results from the latest particle-accelerator experiment. This is not a very satisfactory situation.
This book presents the current views of leading physicists on the bizarre property of quantum theory: nonlocality. Einstein viewed this theory as “spooky action at a distance” which, together with randomness, resulted in him being unable to accept quantum theory. The contributions in the book describe, in detail, the bizarre aspects of nonlocality, such as Einstein–Podolsky–Rosen steering and quantum teleportation—a phenomenon which cannot be explained in the framework of classical physics, due its foundations in quantum entanglement. The contributions describe the role of nonlocality in the rapidly developing field of quantum information. Nonlocal quantum effects in various systems, from solid-state quantum devices to organic molecules in proteins, are discussed. The most surprising papers in this book challenge the concept of the nonlocality of Nature, and look for possible modifications, extensions, and new formulations—from retrocausality to novel types of multiple-world theories. These attempts have not yet been fully successful, but they provide hope for modifying quantum theory according to Einstein’s vision.