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arXiv:2403.06306 · Foundations of Physics

Quantum Physics, Digital Computers, and Life from a Holistic Perspective

George Ellis

Published Aug 1, 2024• 2 citations
arXivHTMLPDF

Abstract

Abstract Quantum physics is a linear theory, so it is somewhat puzzling that it can underlie very complex systems such as digital computers and life. This paper investigates how this is possible. Physically, such complex systems are necessarily modular hierarchical structures, with a number of key features. Firstly, they cannot be described by a single wave function: only local wave functions can exist, rather than a single wave function for a living cell, a cat, or a brain. Secondly, the quantum to classical transition is characterised by contextual wave-function collapse shaped by macroscopic elements that can be described classically. Thirdly, downward causation occurs in the physical hierarchy in two key ways: by the downward influence of time dependent constraints, and by creation, modification, or deletion of lower level elements. Fourthly, there are also logical modular hierarchical structures supported by the physical ones, such as algorithms and computer programs, They are able to support arbitrary logical operations, which can influence physical outcomes as in computer aided design and 3-d printing. Finally, complex systems are necessarily open systems, with heat baths playing a key role in their dynamics and providing local arrows of time that agree with the cosmological direction of time that is established by the evolution of the universe.

DOI
10.1007/s10701-024-00792-4

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Abstract Quantum physics is a linear theory, so it is somewhat puzzling that it can underlie very complex systems such as digital computers and life. This paper investigates how this is possible. Physically, such complex systems are necessarily modular hierarchical structures, with a number of key features. Firstly, they cannot be described by a single wave function: only local wave functions can exist, rather than a single wave function for a living cell, a cat, or a brain. Secondly, the quantum to classical transition is characterised by contextual wave-function collapse shaped by macroscopic elements that can be described classically. Thirdly, downward causation occurs in the physical hierarchy in two key ways: by the downward influence of time dependent constraints, and by creation, modification, or deletion of lower level elements. Fourthly, there are also logical modular hierarchical structures supported by the physical ones, such as algorithms and computer programs, They are able to support arbitrary logical operations, which can influence physical outcomes as in computer aided design and 3-d printing. Finally, complex systems are necessarily open systems, with heat baths playing a key role in their dynamics and providing local arrows of time that agree with the cosmological direction of time that is established by the evolution of the universe.
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Quantum mechanics is one of the cornerstones of modern physics. It governs the behavior and the properties of matter in a fundamental way, in particular on the microscopic scale of atoms and molecules. Hence, what we may call a classical computer, i.e., those machines on or under the desktops in our offices together with all their potential descendants, are themselves following the rules of quantum mechanics. However, they are no quantum computers in the sense that all the inside information processing can perfectly be described within classical information theory. In fact, we do not need quantum mechanics in order to explain how the zeros and ones – the bits – inside a classical computer evolve. The reason for this is that the architecture of classical computers does not make use of one of the most fundamental features of quantum mechanics, namely the possibility of superpositions. Throughout the entire processing of any program on a classical computer, each of the involved bits takes on either the value zero or one. Quantum mechanics, however, would in addition allow superpositions of zeros one ones, that is bits – now called qubits (quantum-bits) – which are somehow in the state zero and one at the
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This paper is an in depth implementation of the proposal (Ellis 2012 Ann. Phys. NY 327 1890–932) that the quantum measurement issue can be resolved by carefully looking at top-down contextual effects within realistic measurement contexts. The specific setup of the measurement apparatus determines the possible events that can take place. The interaction of local heat baths with a quantum system plays a key role in the process. In contrast to the usual attempts to explain quantum measurement by decoherence, we argue that the heat bath follows unitary time evolution only over limited length and time scales (Drossel 2017 His. Phil. Sci. B 58 12–21) and thus leads to localization and stochastic dynamics of quantum particles that interact with it. We show furthermore that a theory that describes all the steps from the initial arrival of the quantum particle to the final pointer deflection must use elements from classical physics. This proposal also provides a contextual answer to the puzzle of the origin of the arrow of time when quantum measurements take place: it derives from the cosmological direction of time. Overall, our proposal is for contextual wavefunction collapse.
The application of quantum mechanics has a dramatic impact in computer sci- ence and engineering. This is because the technology used nowadays to design and explain the functioning of a computer is based on classical mechanics (physics). A ‘classical’ bit can only assume the values ‘0’ or ‘1’ in a mutually exclusive form. As the miniaturization of electronic components will naturally lead to atomic dimensions, quantum mechanics will become one of the few theories capable of providing further advances in computing technology. In ad- dition to biomolecular computers, quantum computers are one of the major promises of a novel computing paradigm.