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Quantum and classical interaction

Quantum and classical interaction

Answering Descartes: Beyond Turing

Stuart Kauffman, University of Vermont & Tampere University

Keywords: Poised realm, decoherence, recoherence, quantum biology

INTRODUCTION: Kauffman is sceptical relative to ideas of consciousness based on classical and macroscopic physics. He proposes instead that consciousness is related to the border area between quantum and classical processing, where the non-algorithmic aspect of the quantum and the non-random aspect of the classical may be mixed. This is termed the 'poised realm', and is seen as applying to systems that include biomolecules and by extension brain systems.

Kauffman summarises the dominant scientific and philosophical view of consciousness, as being the product of a vast network of logic gates in the brain. He says that he thinks that this view is likely to prove wrong. He starts by examining this dominant theory. He relates this to Turing machines or classical computers that are seen as having deterministic behaviour, as a result of being based on algorithms.

The Turing machine idea carried over into computer and brain science, despite the fact that the concept had already run into problems in the philosophical work of Bertrand Russell and Wittgenstein. Later researchers, McCulloch and Pitts, proposed that a system of input neurons with '1' and '0' standing for true and false could compute any logical outcome. They promoted the concept that the true/false or on/off states of a set of neurons was identical to an idea or a thought process existing in the brain. They seems to have been just assumed that sense experiences or qualia were somehow the same as the '1' and '0' processing, although it was never explained why such processing should either require or produce sensory experience. Sensory experience is thus seen by Kauffman, as having been smuggled into the '1' and '0' processing of computers. This approach quickly became an axiom or even a faith statement in consciousness studies despite its lack of firm basis, and in turn accounts for much of the lack of an underlying intellectual rigour in modern consciousness studies.

Kauffman relates this approach to the underlying problem of consciousness and classical physics since Newton. In terms of both classical physics and computer science, the brain is just a deterministic system, comparable to the movement of billiard balls. The problem here is that there is nothing for consciousness/subjective experience to do in such a system. The laws of classical physics plus the initial positions and momenta are sufficient to determine any outcome, leaving consciousness/qualia as an anomaly.

The poised realm
Because of these problems in conventional consciousness studies, Kauffman proposes the idea of the 'poised realm', essentially the border of quantum and classical rules, which he suggests may support processing that is non-algorithmic, but at the same time non-random. This resembles the earlier non-algorithmic scheme proposed by Penrose. Kauffman puts forward the notion of a distinction between 'res potentia', the realm of the possible, or the quantum world, and 'res extensa' the realm of what actually exists, or the classical world. His proposal examines the meaning of the unmeasured or uncollapsed Schrödinger wave, and the question as to whether consciousness can participate at this level.

Kauffman discusses the modern quantum theory approach that distinguishes between an open quantum system and its environment. The open quantum system can be seen as the superposition of many possible quantum particles oscillating in phase. The information of the in-phase quanta can be lost through interaction with the environment, in the process known as decoherence. The information about the peaks and troughs of the Schrödinger wave, and the familiar interference pattern disappears, leading towards a classical system. The process of decoherence takes time, on a scale of one femtosecond. There is a problem regarding the physics of this, because while the mathematical description of the Schrödinger wave is time- reversible, decoherence has traditionally been treated as a time-irreversible dissipative process.

Recoherence: However, it is has in recent years become apparent that recoherence and the creation of a new coherence state is possible, with systems decohering to the point of being effectively classical, and then recohering. Classical information can itself produce recoherence. The Shor quantum error correction theorem shows that in a quantum computer with partially decoherent qubits, a measurement that injects information can bring the qubits back to coherence.

Kauffman, in collaboration with Gabor Vattay, a physicist at Eotvos University Budapest, and Samuli Niiranen, a computer scientist at Tampere University worked out the concept of the 'poised realm' between quantum coherence and classical behaviour. It is in this poised region that Kaufmann suggests non-random, but also non-deterministic processes could arise. Between the open quantum system of the Schrödinger wave and classicality, there is an area that is neither algorithmic nor deterministic, and which is also acausal, and therefore unlike a classical computer. It is suggested that systems can hover between quantum and classical behaviour, this state being what Kaufmann refers to as the 'poised realm'. The non-deterministic processing in the 'poised realm' influences the otherwise deterministic processing of the classical sphere, which can in its turn alter the remaining quantum sphere. There is a two-way interaction between the quantum and classical region. The fact that this process deriving from the classical region is non-random introduces a non-random element into any remaining decoherence in the quantum system. Further, classical parts of the system can recohere, and inject classical information into the quantum system, thus introducing a degree of control into the superpositions of the quanta. In particular, the decision on which amplitudes reach the higher amplitudes, and thus have the greatest probability of decohering can be altered, thus altering the nature of particular classical outcomes.

This leads Kauffman on to discuss the recent discoveries in quantum biology, where quantum coherence and entanglement have been demonstrated in living photosynthetic organisms. The suggestion is that biomolecules are included in the systems that can hover between the quantum and the classical region, and further that this could apply not only to photosynthetic biomolecules, but also to biomolecules within neurons. Thus brain systems could be allowed to recohere to introduce further acausality into the system. Kaufmann views consciousness as a participation in res potentia and its possibilities. The presence of consciousness in the res potentia is also suggested to explain the lack of an apparent spatial location for consciousness. Qualia are suggested to be related to quantum measurement in which the possible becomes actual.

However, Kaufmann admits that all this still contains no real explanation of sensory experience. Kaufmann acknowledges that he is looking for something similar to Penrose, but thinks it may be located in the poised realm rather than in Penrose's objective reduction. Where the earlier scheme of Penrose still has the advantage is in the rounding off proposition that his objective reduction gives access to consciousness at the level of the fundamental spacetime geometry. Presumably Kaufmann assumes something of the kind. There is no particular reason why either quanta or classical structures or some mixture of them should be conscious, but we know that the quanta relate to fundamental properties such as charge and spin and to spacetime, and it seems reasonable on the same basis to look for consciousness as a fundamental property at this level.