How quantum is life

How quantum paradoxes suggest physical "probabilities" hide an interface for free will

This was written for the 2025 FQXI essay contest "How quantum is life" but rejected by moderators

Abstract. Quantum mechanics may play two kinds of roles in biology according to its two evolution laws. While unitary evolution features quantum effects (entanglement, tunneling...) which may play key technical roles in biology, their predictable nature makes them unsuitable as a conceptual foundation to explain consciousness. Physicalist views, especially the hidden variables and objective collapse interpretations of quantum physics, suffer heavy paradoxes, while the mind makes collapse interpretation gives a better solution, using wave function collapse deviating from Born's rule as an expression of free will.

Introduction

The dynamics of state reduction (usually called wave function collapse, but quantum states may be conceived as density operators instead of wave functions), was already interpreted as an act of consciousness by pioneers of quantum physics such as von Neumann and Wigner. This idea then lost popularity among scientists, as works on quantum foundations focused on developing and comparing other (physicalist) interpretations. Meanwhile, diverse ideas of links between consciousness and quantum physics came but suffered respective flaws.
Yet, not all possible kinds of such links must be rejected. We shall explain some needed features for a mind makes collapse interpretation to better match modern physics, after reviewing diverse shortcomings of physicalism.

Quantumness of predictable effects

The question of "how quantum" are given predictable physical phenomena, depends on the scale of their description. All laws of chemistry are crucially based on those of quantum physics at atomic scales. Then, most biochemical phenomena admit essentially classical explanations once admitted a long list of rules describing the most common molecules and basic reactions around molecular scales.
Some exceptions remain, of biochemical processes not well explained by classical chemical representations, due to quantum features occurring at some larger scale than those usually underlying basic chemistry. This may rely on a role of spins, special molecular orbitals beyond the scheme of successive covalent bonds, or a quantum behavior of hydrogen atoms (whose lower mass may allow them larger typical position uncertainty). Such processes are then qualified as "quantum".
But, this qualification remains largely conventional, for the following reason.

Imagine a classical supercomputer doing the following operations.
First, list all molecules or parts of molecules likely to occur in biological systems, up to about 20 or 30 atoms.
Then, explore their possible quantum properties by simulating the laws of quantum mechanics, representing any qbits by their coordinates. The possibly large needed computer resources at this step, will be balanced by the fact each configuration needs to be analyzed only once, while it may occur many times in large organisms.
Quantum effects in larger molecules will be inferred by successive applications of those first identified in smaller groups of atoms they are made of. Quantum features involving distant parts of a molecule, may be inferred from those of successive smaller groups of atoms, along which a qbit may propagate. Possible quantum features of special interactions between two neighboring molecules or parts of larger molecules, will be also analyzed.

Then, behaviors of larger systems are simulated by basically using the classical chemical representation, but tracking there all occurrences of configurations where quantum effects were found to occur, to apply these corrections and effects to the simulation.
This is indeed likely to approach the exact consequences of quantum mechanics, due to the normal context of biochemistry which leads to fast decoherence, not letting superposition and interference intervene at larger scales or with more than a couple of qbits. By contrast, quantum computers and quantum communication systems require very special hardware not found in typical biochemistry.

Now, two philosophical or terminological questions may be asked about this supercomputer:

Should its operation be called "quantum" ?

Its working was assumed to be classical in its basic logical layer. Quantum features are only simulated at upper layers by software design. So, calling its operation "quantum" is a mere matter of convention to qualify that higher logical layer, not anything fundamental.

Does it process "real life" ?
Under the physicalist assumption that quantum physics is accurate as a probabilistic theory, this simulation would closely approach the outcomes of real biological systems, with small differences due to the limits of available computer resources. Such differences would not easily justify to remove the title of "life" for the simulation. Indeed, a general feature of life is its diversity and flexibility to thrive through diverse environments, given a planet with liquid water and so on, but not depending on further miraculously fine-tuned condition. Therefore, a marginal change in basic laws, such as the move from exact to tentatively simulated outcomes of quantum mechanics, would only moderately affect the development of life, namely requiring some changes in DNA codes to work better with the modified laws. Such variations would be largely contained by those typical of the natural diversity of life, with its diverse species all qualified as genuine instances of "life", and even "conscious life" (seeing familiar animals as conscious).

A philosophical way out might be to let the titles of "life" and "consciousness" crucially depend on the underlying hardware, even for the same outcomes. This leads to paradoxes, such as its ambiguity on hybrid forms of life with artificial brain parts, and the open door to solipsism (a brain in a vat cannot check other people's hardware).

So, no matter the technical roles of quantum effects in biology, the idea they might be crucial to explain consciousness in a philosophical sense would be hard to defend, insofar as quantum mechanics is valid as a probabilistic theory. The rest of this essay will explore the alternative option: that conscious life may diverge from its predictions.

Physicalist interpretations

The dynamics of state reduction appears probabilistic and working like a black box. Its details (whether, when or how it really occurs), remain unknown and the matter of debate between interpretations.

Both hidden variables and objective collapse interpretations, see measurements as truly making only one result "real" at random, by some process basically unrelated to life and consciousness. In such cases, any deviation of outcomes from the standard predictions of quantum mechanics is likely to be small and neutral on the behavior of life, in a probabilistic sense. However, these interpretations suffer heavy paradoxes as follows.

On the physical side, attempts to specify them by candidate hidden details for the measurement process, clash with modern physics as it stands.
For instance, the details of roughly simultaneous measurements on entangled particles would depend on a time order between both measurements, breaking relativistic invariance which is a cornerstone of modern physics. Two kinds of physical laws, the one fundamentally relying on relativistic invariance, the other breaking it, would be hard to articulate.
More of such physical reasons based on general features of quantum field theory, is given by Wallace [1], concluding as

"when we recognise the real structure of quantum theory (...) most extant approaches to the quantum measurement problem should be recognised as inadequate to that real structure (...) either the Everett interpretation is viable (...) or else it must be rejected for some philosophical or technical reason, in which case there is at present no adequate interpretation of quantum theory."

Another trouble is philosophical : an objective collapse theory giving rules of occurrence for state reduction by the projection postulate, can only let it occur roughly after decoherence, to stay compatible with the lack of known effects from experiments incidentally measuring the interference from coherent states on which it would act. However, decoherence is an emergent, inexpressible condition ([2], pp. 16-17) :

"...the set of exactly decoherent history spaces is huge...", while the intuitive criterion to try to specify one, "quasi-classicality is pretty unsatisfactory. For one thing, it is essentially vague (...) For another, it is a high-level notion all-but-impossible to define in microphysical terms".

Hence, expressible laws roughly fitting the "after decoherence" requirement which lacks a clear measure, will also let most cases of state reduction occur much slower than decoherence, to an extent which no principle is likely to limit. This leads to a paradox in the style of Schrödinger's cat ([2], p.39) :

"...the speed of collapse should be chosen so as to prevent “the embarrassing occurrence of linear superpositions..." (...) One natural criterion is that the superpositions should collapse before humans have a chance to observe them. But the motivation for this is open to question. (...) Now suppose that the collapse is much slower, taking several seconds to occur. Then the cat-observer system enters the superposition (...) in a few seconds the state collapses (...) the agent will have no memory of the superposition. So the fast and slow collapses appear indistinguishable empirically."

Hidden variables theories may suffer a similar issue: in Bohmian mechanics, when wave packets of a wave function collide, the "particle" can switch between them. More generally, this theory fails to match classical approximations [3]:

"Bohmian mechanics spoils the quantum-classical correspondence that arises in the semiclassical regime (...) Bohmian trajectories will necessarily remain unrelated to the properties of the corresponding classical system, and will be unable to explain the manifestations of chaotic classical trajectories in quantum systems"

Whether decoherence improves the situation remains unclear, as an analysis [4] focused on a particular case, leaving open the general question. Indeed by the fuzziness of decoherence, the claim at any time that the hidden variable selected one outcome, remains ill-defined. Thus, no clear philosophical principle ensures this selection to be preserved in time. Whether it is preserved, is a hard technical question dependent on a choice of hidden variables theory. But, it is superseded by the following philosophical argument.

Imagine two hidden variables theories A and B were found matching our best physics, where outcomes cannot switch anymore after conscious observation according to A, but can still switch according to B. How should a proponent of the hidden variables interpretation react to this ?

If this is an advantage of A over B, this means the viewpoint of conscious observers should matter to the resolution of the measurement problem. This contradicts the claimed preference for hidden variables, and generally any physicalist interpretation, over a mind makes collapse interpretation. Indeed if there is a philosophical need that outcomes remain fixed after conscious observation, then this feature would more naturally be an explicit fundamental principle, than an empirically empty, sophisticated coincidence
But if this difference does not matter, then one should directly assume that in the style of Last Thursdayism, selections keep switching many times after conscious observation, for correctly assessing the hidden variables interpretation against many-worlds. In these terms, many-worlds seems to fare better.

Either way, the hidden variables interpretation appears philosophically unmotivated. The same argument also undermines objective collapse theories with their choice of collapse rate.

Another odd feature of both hidden variables and objective collapse theories, is their need to postulate an endless source of randomness which appears unbiased, may they explicitly describe it or not (in Bohmian mechanics, this is the infinite sequence of decimals of the continuous hidden variable). One may wonder why and how such an invisible source would exist in nature.

Adding these philosophical issues to the physical ones, confirms the superiority of many-worlds among physicalist interpretations which effectively attempt to describe reality. The last question would then be to assess many-worlds against mind makes collapse. Noteworthily, since proponents of objective collapse usually do require fast collapse rates for macroscopic observers, the above argument logically puts them on the side of mind makes collapse against many-worlds.

Also, many-worlds faces some tough criticism, such as [5], or Jean Bricmont who claims that “there is no existing alternative to de Broglie-Bohm that reaches the level of clarity and explanatory power of the latter”, as quoted by Callender [6] who also points out the general need of a clearly best solution to the measurement problem, since a persisting controversy would be at odds with scientific realism. This unease is also expressed by Carroll [7].

Oddly thus, the popularity of physicalism among scientists, does not appear followed by that of its deep logical consequences, which only a minority seems aware of ; others logically ought to face the challenge of either taking these consequences seriously, searching for a logical way out, or questioning their physicalist assumptions.

A more general oddity of physicalism, is its reduction of consciousness to classical computations, explained earlier. This reduction has far-reaching paradoxical consequences, such as the possibilities of mind uploading and mind cloning which lead to the teletransportation paradox, or of being unexpectedly switched off. More of such consequences have been explored for example in [8].

The natural way out of all above paradoxes, is to see consciousness as not reducible to the operation of any fixed algorithm. We shall show this by sketching a non-physicalist view based on this principle.

State reduction as an expression of free will

If consciousness is not material and its behavior escapes mathematical determination, then its action on matter is likely to take the form of state reduction. According to Chalmers [9] :

" The collapse dynamics leaves a door wide open for an interactionist interpretation (...) Collapse is supposed to occur on measurement (...) it seems that no purely physical criterion for a measurement can work (...) it is natural to suggest that a measurement is precisely a conscious observation (...) In fact, one might argue that if one was to design elegant laws of physics that allow a role for the conscious mind, one could not do much better than the bipartite dynamics of standard quantum mechanics: one principle governing deterministic evolution in normal cases, and one principle governing nondeterministic evolution in special situations that have a prima facie link to the mental. (...) There is some irony in the fact that philosophers reject interactionism on largely physical grounds (...) while physicists reject an interactionist interpretation of quantum mechanics on largely philosophical grounds"

We shall expand on this as follows: while the objective collapse interpretation mainly suffers the difficulty to specify a mathematical law for state reduction articulated with current physics, this trouble no more affects a mathematically lawless state reduction with a different metaphysical status beyond physical laws.

Conditions of state reduction

One issue with objective collapse, was the problem of locating state reduction events at specific physical times, in contrast with their spatial non-locality, while any involvement of a time slice in physical space-time would be at odds with the relativity of simultaneity. For mind makes collapse, two options may be considered.

If state reduction events remain localized in physical time, namely at least contained by some microseconds-thick simultaneity slice, then decoherence cannot be rigorously complete, and might even be reversible in principle. In this case, two successive state reductions described by the projection postulate, can in principle give a state whose probability by a single measurement was 0. This aspect, in common with objective collapse theories, raises two issues:

It may be subject to the same forms of testability. But, tests of objective collapse theories have been negative [10].
It removes what naturally ensured energy conservation to stay essentially valid through state reduction. Some other special requirement then needs to be put on the form of state reduction, for energy conservation to still exactly hold at the microphysical level, as mathematically required by General Relativity. But, such requirements may be uneasy to express, since energy cannot be exactly measured in finite time according to a Heisenberg inequality.

On the other hand, the criterion of decoherence, which emerges as a future limit condition with respect to microphysics, can be postulated to be a strict condition of possibility for a state reduction "event" conceived as fully non-local, "occurring" outside microphysical space-time. For this, a hidden side of consciousness may have developed the non-mathematizable skill to pick at will particular instances of quasi-classical decoherence conditions, distinguishing macro-states which decohered states appear superpositions of.

Selected results of state reduction

Choices of measurement histories have no physically testable effects, as long as strict decoherence conditions are fulfilled and outcomes follow physical probabilities. Thus, for a mind to effectively act on matter by operating a decoherent history, requires at least some outcomes of state reduction events to be chosen from possibilities, instead of being all left at random.
This option is often accused of breaking the laws of physics, but this argument is not clear. Indeed, both free will and randomness are characterized by a lack of mathematical determination. They only differ in intuitive terms :

We have an intuitive idea where a free will choice is from, namely from a mind escaping mathematical description.
Randomness following a probability law, means the source of choice is supposed to be an absolute, irreducible mystery. Indeed, any concept of the nature of this source would require an explanation why its outcomes seem to fit given probabilities, which would lose their status as a fundamental law so deeply written in the formalism of quantum theory. It is also unclear whether a probability law is a law at all in a metaphysical sense. Indeed, to make it better look like one, would involve averaging across many similar trials; but this criterion, however useful for repetitive experiences (a mere special extract from natural cases), lacks metaphysical sharpness.

It seems odd, then, that randomness is usually seen clearer than free will as a metaphysical foundation. It also seems odd that decoherent history was ruled out by Wallace as "the solution that isn't" just due to its mathematical lawlessness, by contrast with an objective collapse interpretation requiring an underlying mathematical determination which looks hopeless to specify and would probably keep the source of randomness mysterious anyway.

By contrast, free will, namely choices escaping mathematical and even probabilistic determination, can serve as the unified foundation for both aspects of state reduction.

Shares of random vs willful events

A usual argument against the relevance of quantum mechanics in brain behavior, is that the main source of randomness in biochemistry is thermal noise, assumed to be a classical, deterministic randomness. It was so seen since statistical physics was first developed from classical mechanics where all is deterministic. Yet, while most features of the classical analysis remain valid, the metaphysical source of randomness is an exception. Indeed, the study of statistical physics in the quantum framework reveals that all thermal randomness has a quantum source [11][12], thus keeps superposition until "measurement". Therefore, the pervasiveness of thermal noise in biochemistry is actually a perfect source of wide opportunity of expression of free will in brains via state reduction results, not an obstacle to it.

In practice, most state reduction results in nature, especially those of typical physics experiments, look random; the expression of free will in brains forms a much smaller information flow. Their coexistence gives the following hints on the hidden structures of consciousness (only fuzzily describable, as they escape mathematization). The whole of consciousness needs to be much broader than the sum of the minds of familiar individuals, to account for the full spectrum of aspects of its physical expressions:

The discernment of decoherent states in microphysics;
Many details getting filled at intermediate scales, seemingly at random following physical probabilities;
The free will of humans and animals.

The divisions between these need not be strict. The share of outcomes between randomness and expressions of familiar free will, need not be determined by any physical criterion, such as occurrences of "quantum" aspects of biochemistry ; it is rather up to the hidden structures of consciousness to form this division. Superpositions produced outside living bodies are likely to give random outcomes, by lack of clear attribution of their first perception to a known observer. Even then, the first known observer of a freshly produced superposition may bring a bias to its randomness. This is the phenomenon called mind-matter interaction or PK (psychokinesis) investigated in parapsychology [13][14].

One experiment [15] is presented as precognition for a random process triggered by pressing the button expressing the guess. Yet as admitted in the article, "The experimental setup... does not permit a distinction between precognition and psychokinesis". It would actually be hard to metaphysically understand it as precognition, since the outcome of a random event whose triggering decision is yet to come can hardly be considered predetermined; indeed the most successful subject took it as a PK experiment. An unambiguous guessing experiment could instead be made using a pre-recorded sequence of random data first displayed where no human was looking (to fix it by non-human observation). Then, any extrasensorial perception obviously gets expressed from the mind to the brain like any free will, by brain functions deviating from physical probabilities.

References

[1] D. Wallace (2018), "On the Plurality of Quantum Theories: Quantum theory as a framework, and its implications for the quantum measurement problem", S. French and J. Saatsi, Scientific Realism and the Quantum (OUP, 2020),
http://philsci-archive.pitt.edu/15292/

[2] D. Wallace (2007), The Quantum Measurement Problem: State of Play, arXiv:0712.0149

[3] A. Matzkin & V. Nurock (2008), Classical and Bohmian trajectories in semiclassical systems: Mismatch in dynamics, mismatch in reality? Studies in History and Philosophy of Modern Physics 39, 17-40,
https://matzkin.u-cergy.fr/fichiers/2008-Bohmian-Real.pdf

[4] D. M. Appleby (1999), Bohmian Trajectories Post-Decoherence, Found.Phys. 29 1885-1916, arXiv:quant-ph/9908029

[5] P. Ball (2018), Why the Many-Worlds Interpretation Has Many Problems, Quanta Magazine,
https://www.quantamagazine.org/why-the-many-worlds-interpretation-has-many-problems-20181018/

[6] C. Callender (2018), Can We Quarantine the Quantum Blight?
https://philsci-archive.pitt.edu/15450/

[7] S. Carroll, The Most Embarrassing Graph in Modern Physics (blog post),
https://www.preposterousuniverse.com/blog/2013/01/17/the-most-embarrassing-graph-in-modern-physics/

[8] M. Séguin (2015), My God, It’s Full of Clones: Living in a Mathematical Universe,
FQXI Trick or Truth Essay Contest,
https://forums.fqxi.org/d/2497-my-god-its-full-of-clones-living-in-a-mathematical-universe-by-marc-seguin

[9] David Chalmers (2002), Consciousness and its Place in Nature, In The Blackwell Guide to the Philosophy of Mind. Blackwell. pp. 102--142 (2003),
https://philpapers.org/rec/CHACAI-7

[10] P. Ball (2022), Experiments Spell Doom for Decades-Old Explanation of Quantum Weirdness, Quanta magazine,
https://www.quantamagazine.org/physics-experiments-spell-doom-for-quantum-collapse-theory-20221020/

[11] P. Ball (2022), Physicists Rewrite the Fundamental Law That Leads to Disorder, Quanta Magazine,
https://www.quantamagazine.org/physicists-trace-the-rise-in-entropy-to-quantum-information-20220526/

[12] D. Wallace (2016), Probability and Irreversibility in Modern Statistical Mechanics: Classical and Quantum, arXiv:2104.11223

[13] M. Dechamps (2019), Mind-matter interactions and their reproducibility. PhD thesis at Ludwig-Maximilians-Universität München,
https://edoc.ub.uni-muenchen.de/25403/1/Dechamps_Moritz.pdf

[14] R. D. Nelson (2024), Global Consciousness: Manifesting Meaningful Structure in Random Data, Journal of Anomalous Experience and Cognition 2024,Vol.4,No.2,pp.149-173
https://journals.lub.lu.se/jaex/article/view/25553/23598

[15] H. Schmidt (2018), Precognition of a Quantum Process, Journal of Parapsychology, Vol. 82, Suppl., 87-95
https://parapsych.org/uploaded_files/pdfs/00/00/00/00/94/07_schmidt_precognition_of_a_quantum_process.pdf