# Diederik AertsVrije Universiteit Brussel | VUB · Center Leo Apostel (CLEA)

Diederik Aerts

Professor

## About

346

Publications

49,051

Reads

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7,506

Citations

Citations since 2017

Introduction

My research is mainly in Foundations of Quantum Mechanics, and more specifically in Quantum Cognition, a domain which applies quantum structure to model parts of human cognition and decision making.

## Publications

Publications (346)

Inspired by foundational studies in classical and quantum physics, and by information retrieval studies in quantum information theory, we prove that the notions of ‘energy’ and ‘entropy’ can be consistently introduced in human language and, more generally, in human culture. More explicitly, if energy is attributed to words according to their freque...

In physics, entanglement ‘reduces’ the entropy of an entity, because the (von Neumann) entropy of, e.g., a composite bipartite entity in a pure entangled state is systematically lower than the entropy of the component sub-entities. We show here that this ‘genuinely non-classical reduction of entropy as a result of composition’ also holds whenever t...

We present the results of two tests where a sample of human participants were asked to make judgements about the conceptual combinations The Animal Acts and The Animal eats the Food. Both tests significantly violate the Clauser-Horne-Shimony-Holt version of Bell inequalities (‘CHSH inequality’), thus exhibiting manifestly non-classical behaviour du...

We argue that the construction of spacetime is personal, specific to each observer, and requires combining aspects of both discovery and creation. What is usually referred to as the block universe then emerges by noting that part of the future is contained in the present, but without the limitations that the four-dimensional block universe usually...

We consider a simple string model to explain and partly demystify the phenomenon of quantum entanglement. The model in question has nothing to do with string theory: it uses macroscopic strings that can be acted upon by Alice and Bob in ways that violate, or fail to violate, in different ways Bell-CHSH inequalities and the no-signaling conditions,...

In physics, entanglement 'reduces' the entropy of an entity, because the (von Neumann) entropy of, e.g., a composite bipartite entity in a pure entangled state is systematically lower than the entropy of the component sub-entities. We show here that this 'genuinely non-classical reduction of entropy as a result of composition' also holds whenever t...

Inspired by foundational studies in classical and quantum physics, and by information retrieval studies in quantum information theory, we have recently proved that the notions of 'energy' and 'entropy' can be consistently introduced in human language and, more generally, in human culture. More explicitly, if energy is attributed to words according...

For two decades, the formalism of quantum mechanics has been successfully used to describe human decision processes, situations of heuristic reasoning, and the contextuality of concepts and their combinations. The phenomenon of `categorical perception’ has put us on track to find a possible deeper cause of the presence of this quantum structure in...

We wish to investigate the ways in which the quantum structures of superposition, contextuality, and entanglement have their origins in human perception itself, given how they are sucessfully used to model aspects of human cognition. Our analysis takes us from a simple quantum measurement model, along how human perception incorporates the warping m...

As a result of the identification of “identity” and “indistinguishability” and strong experimental evidence for the presence of the associated Bose-Einstein statistics in human cognition and language, we argued in previous work for an extension of the research domain of quantum cognition. In addition to quantum complex vector spaces and quantum pro...

As a result of the identification of 'identity' and 'indistinguishability' and strong experimental evidence for the presence of the associated Bose-Einstein statistics in human cognition and language, we argued in previous work for an extension of the research domain of quantum cognition. In addition to quantum complex vector spaces and quantum pro...

Following in the footsteps of Schrödinger, we propose a unified view of matter, life and human culture, with particular emphasis on the role played by the second law of thermodynamics and the primordial matter–antimatter separation. In doing so, we highlight the fragility of ‘construction’ (order) and the robustness of ‘destruction’ (chaos), when t...

In previous research, we showed that ‘texts that tell a story’ exhibit a statistical structure that is not Maxwell–Boltzmann but Bose–Einstein. Our explanation is that this is due to the presence of ‘indistinguishability’ in human language as a result of the same words in different parts of the story being indistinguishable from one another, in muc...

Quantum structures were identified as relevant for describing situations occurring in human cognition in the domain of quantum cognition and were also fruitfully used in information retrieval and natural language processing in the domain of quantum information theory. In the present article, we build on recent prior work and show that additionally...

We describe a simple experimental setting where joint measurements performed on a single (classical or quantum) entity can violate both the Bell-CHSH inequality and the marginal laws (also called no-signaling conditions). Once emitted by a source, the entity propagates within the space of Alice’s and Bob’s detection screens, with the measurements’...

In this article we solve this ancient problem of perfect tuning in all keys and present a system were all harmonies are conserved at once. It will become clear, when we expose our solution, why this solution could not be found in the way in which earlier on musicians and scientist have been approaching the problem. We follow indeed a different appr...

We present the fundamentals of the quantum theoretical approach we have developed in the last decade to model cognitive phenomena that resisted modeling by means of classical logical and probabilistic structures, like Boolean, Kolmogorovian and, more generally, set theoretical structures. We firstly sketch the operational-realistic foundations of c...

A correction to this paper has been published: https://doi.org/10.1007/s10699-021-09793-2

We present the results of two tests where a sample of human participants were asked to make judgements about the conceptual combinations {\it The Animal Acts} and {\it The Animal eats the Food}. Both tests significantly violate the Clauser-Horne-Shimony-Holt version of Bell inequalities (`CHSH inequality'), thus exhibiting manifestly non-classical...

We work out a quantum-theoretic model in complex Hilbert space of a recently performed test on co-occurrencies of two concepts and their combination in retrieval processes on specific corpuses of documents. The test violated the Clauser-Horne-Shimony-Holt version of Bell’s inequalities (‘CHSH inequality’), thus indicating the presence of entangleme...

We model a piece of text of human language telling a story by means of the quantum structure describing a Bose gas in a state close to a Bose–Einstein condensate near absolute zero temperature. For this we introduce energy levels for the words (concepts) used in the story and we also introduce the new notion of ‘cogniton’ as the quantum of human th...

How can we explain the strange behavior of quantum and relativistic entities? Why do they behave in ways that defy our intuition about how physical entities should behave, considering our ordinary experience of the world around us? In this article, we address these questions by showing that the comportment of quantum and relativistic entities is no...

It is well known that correlations produced by common causes in the past cannot violate Bell's inequalities. This was emphasized by Bell in his celebrated example of Bertlmann's socks. However, if common causes are contextual, i.e., actualized at each run of a joint measurement, in a way that depends on the type of joint measurement that is being e...

We provide a general description of the phenomenon of entanglement in bipartite systems, as it manifests in micro and macro physical systems, as well as in human cognitive processes. We do so by observing that when genuine coincidence measurements are considered, the violation of the ‘marginal laws’, in addition to the Bell-CHSH inequality, is also...

Conceptual entanglement is a crucial phenomenon in quantum cognition because it implies that classical probabilities cannot model non--compositional conceptual phenomena. While several psychological experiments have been developed to test conceptual entanglement, this has not been explored in the context of Natural Language Processing. In this pape...

We model a piece of text of human language telling a story by means of the quantum structure describing a Bose gas in a temperature close to a Bose-Einstein condensate near absolute zero. For this we introduce energy levels for the concepts (words) used in the story and we also introduce the new notion of 'cogniton' as the quantum of human language...

We show that the Brussels operational-realistic approach to quantum physics and quantum cognition offers a fundamental strategy for modeling the meaning associated with collections of documental entities. To do so, we take the World Wide Web as a paradigmatic example and emphasize the importance of distinguishing the Web, made of printed documents,...

We motivate the possibility of using notions and methods derived from quantum physics, and more specifically from the research field known as ‘quantum cognition’, to optimally model different situations in the field of medicine, its decision-making processes and ensuing practices, particularly in relation to chronic and rare diseases. This also as...

We describe a simple experimental setting where joint measurements performed on a single (classical or quantum) entity can violate both the Bell-CHSH inequality and the no-signaling conditions. Our analysis shows that the violation of the latter does not necessarily imply the possibility of a superluminal communication, as it is often believed due...

Since its inception, many physicists have seen in quantum mechanics the possibility, if not the necessity, of bringing cognitive aspects into the play, which were instead absent, or unnoticed, in the previous classical theories. In this article, we outline the path that led us to support the hypothesis that our physical reality is fundamentally con...

We provide a general description of the phenomenon of entanglement in bipartite systems, as it manifests in micro and macro physical systems, as well as in human cognitive processes. We do so by observing that when genuine coincidence measurements are considered, the violation of the 'marginal laws', in addition to the Bell-CHSH inequality, is also...

We work out a quantum-theoretic model in complex Hilbert space of a recently performed test on co-occurrencies of two concepts and their combination in retrieval processes on specific corpuses of documents. The test violated the Clauser-Horne-Shimony-Holt version of the Bell inequalities ('CHSH inequality'), thus indicating the presence of entangle...

Recent years have been characterized by tremendous advances in quantum information and communication, both theoretically and experimentally. In addition, mathematical methods of quantum information and quantum probability have begun spreading to other areas of research, beyond physics. One exciting new possibility involves applying these methods to...

We motivate the possibility of using notions and methods derived from quantum physics, and more specifically from the research field known as 'quantum cognition', to optimally model different situations in the field of medicine, its decision-making processes and ensuing practices, particularly in relation to chronic and rare diseases. This also as...

We put forward a new view of relativity theory that makes the existence of a
flow of time compatible with the four-dimensional block universe. To this end,
we apply the creation-discovery view elaborated for quantum mechanics to
relativity theory and in such a way that time and space become creations
instead of discoveries and an underlying non-tem...

We show that the Brussels operational-realistic approach to quantum physics and quantum cognition offers a fundamental strategy for modeling the meaning associated with collections of documental entities. To do so, we take the World Wide Web as a paradigmatic example and emphasize the importance of distinguishing the Web, made of printed documents,...

We performed a cognitive experiment in which we asked the participants to
pick a pair of directions they considered as the 'preferred good example of two
different wind directions'. The results of the experiment reveal that the
'Clauser Horne Shimony Holt' (CHSH) form of Bell inequalities is violated. The
violation is significant and, amazingly eno...

Expected utility theory (EUT) is widely used in economic theory. However, its subjective probability formulation, first elaborated by Savage, is linked to Ellsberg-like paradoxes and ambiguity aversion. This has led various scholars to work out non-Bayesian extensions of EUT which cope with its paradoxes and incorporate attitudes toward ambiguity....

In the first half of this two-part article, we analyzed a cognitive psychology experiment where participants were asked to select pairs of directions that they considered to be the best example of 'Two Different Wind Directions', and showed that the data violate the CHSH version of Bell's inequality, with same magnitude as in typical Bell-test expe...

Non-Newtonian calculus that starts with elementary non-Diophantine arithmetic operations of a Burgin type is applicable to all fractals whose cardinality is continuum. The resulting definitions of derivatives and integrals are simpler from what one finds in the more traditional literature of the subject, and they often work in the cases where the s...

Since its inception, many physicists have seen in quantum mechanics the possibility, if not the necessity, of bringing cognitive aspects into the play, which were instead absent, or unnoticed, in the previous classical theories. In this article, we outline the path that led us to support the hypothesis that our physical reality is fundamentally con...

In psychological measurements, two levels should be distinguished: the 'individual level', relative to the different participants in a given cognitive situation, and the 'collective level', relative to the overall statistics of their outcomes, which we propose to associate with a notion of 'collective participant'. When the distinction between thes...

We present a view of the evolving reality based on our understanding of the recently discovered (in the time scale of human evolution) quantum laws, how they manifest at the different organizational levels of inert matter, living organisms and cultural artifacts, and what they possibly imply regarding the nature of the stuff the world is made of. W...

The quantum formalism can be completed by assuming that a density operator can also represent a pure state. An 'extended Bloch representation' (EBR) then results, in which not only states, but also the measurement-interactions can be represented. The Born rule is obtained as an expression of the subjective lack of knowledge about the measurement-in...

The ‘conjunction fallacy’ has been extensively debated by scholars in cognitive science and, in recent times, the discussion has been enriched by the proposal of modeling the fallacy using the quantum formalism. Two major quantum approaches have been put forward: the first assumes that respondents use a two-step sequential reasoning and that the fa...

The Machina thought experiments pose to major non-expected utility models challenges that are similar to those posed by the Ellsberg thought experiments to subjective expected utility theory (SEUT). We test human choices in the `Ellsberg three-color example', confirming typical ambiguity aversion patterns, and the `Machina 50/51 and reflection exam...

The mathematical formalism of quantum theory exhibits significant effectiveness when applied to cognitive phenomena that have resisted traditional (set theoretical) modeling. Relying on a decade of research on the operational foundations of micro-physical and conceptual entities, we present a theoretical framework for the representation of concepts...

We show that the extended Bloch representation of quantum mechanics also applies to infinite-dimensional entities, to the extent that the number of (possibly infinitely degenerate) outcomes of a measurement remains finite, which is always the case in practical situations.

This is a book presenting to a wide audience of readers, ranging from fans of science to professional researchers, some of the authors' recent discoveries in three distinct, but intimately related domains: probability theory (Bertrand's paradox), observation in physics (the measurement problem) and the modeling of experiments in psychology (quantum...

We elaborate a quantum model for corpora of written documents, like the pages forming the World Wide Web. To that end, we are guided by how physicists constructed quantum theory for microscopic entities, which unlike classical objects cannot be fully represented in our spatial theater. We suggest that a similar construction needs to be carried out...

The standard Bloch sphere representation was recently generalized to the
'extended Bloch representation' describing not only systems of arbitrary
dimension, but also their measurements. This model solves the measurement
problem and is based on the 'hidden-measurement interpretation', according to
which the Born rule results from our lack of knowled...

The ‘quantum cognition’ paradigm was recently challenged by its proven impossibility to simultaneously model ‘question order effects’ and ‘response replicability’. In the present article we describe sequential dichotomic measurements within an operational and realistic framework for human cognition, and represent them in a quantum-like ‘extended Bl...

The authors provide an overview of the results they have obtained over the last decade on the identification of quantum structures in cognition and, more specifically, in the formalization and representation of natural concepts. They firstly discuss the quantum foundational reasons that led them to investigate the mechanisms of formation and combin...

The mathematical formalism of quantum theory exhibits significant effectiveness when applied to cognitive phenomena that have resisted traditional (set theoretical) modeling. Relying on a decade of research on the operational foundations of micro-physical and conceptual entities, we present a theoretical framework for the representation of concepts...

We present a very general geometrico-dynamical description of physical or more abstract entities, called the general tension-reduction (GTR) model, where not only states, but also measurement-interactions can be represented, and the associated outcome probabilities calculated. Underlying the model is the hypothesis that indeterminism manifests as a...

Entangled states are in conflict with a general physical principle which expresses that a composite entity exists if and only if its components also exist, and the hypothesis that pure states represent the actuality of a physical entity, i.e., its ‘existence’. A possible way to solve this paradox consists in completing the standard formulation of q...

The formalism that starts with elementary non-Diophantine arithmetic operations of a Burgin type can be naturally incorporated into fractals more complicated than just the Cantor set. In particular, the resulting calculus on Sierpi\'nski sets is much simpler from what one finds in the more traditional literature of the subject. As an application we...

The formalism of quantum theory in Hilbert space has been applied with success to the modeling and explanation of several cognitive phenomena, whereas traditional cognitive approaches were problematical. However, this 'quantum cognition paradigm' was recently challenged by its proven impossibility to simultaneously model 'question order effects' an...

The research on human cognition has recently benefited from the use of the mathematical formalism of quantum theory in Hilbert space. However, cognitive situations exist which indicate that the Hilbert space structure, and the associated Born rule, would be insufficient to provide a satisfactory modeling of the collected data, so that one needs to...

Theories of natural language and concepts have been unable to model the flexibility, creativity, context-dependence, and emergence, exhibited by words, concepts and their combinations. The mathematical formalism of quantum theory has instead been successful in capturing these phenomena such as graded membership, situational meaning, composition of...

Fractals equipped with intrinsic arithmetic lead to a natural definition of differentiation, integration and complex numbers. Applying the formalism to the problem of a Fourier transform on fractals we show that the resulting transform has all the expected basic properties. As an example we discuss a sawtooth signal on the ternary middle-third Cant...

The purpose of the present note is twofold. Firstly, we highlight the
similarities between the ontologies of Kastner's possibilist transactional
interpretation (PTI) of quantum mechanics - an extension of Cramer's
transactional interpretation - and the authors' hidden-measurement
interpretation (HMI). Secondly, we observe that although a weighted s...

We recently performed cognitive experiments on conjunctions and negations of
two concepts with the aim of investigating the combination problem of concepts.
Our experiments confirmed the deviations (conceptual vagueness, underextension,
overextension, etc.) from the rules of classical (fuzzy) logic and probability
theory observed by several scholar...

The scientific community is becoming more and more interested in the research
that applies the mathematical formalism of quantum theory to model human
decision-making. In this paper, we provide the theoretical foundations of the
quantum approach to cognition that we developed in Brussels. These foundations
rest on the results of two decade studies...

We present a very general geometrico-dynamical description of physical or
more abstract entities, called the 'general tension-reduction' (GTR) model,
where not only states, but also measurement-interactions can be represented,
and the associated outcome probabilities calculated. Underlying the model is
the hypothesis that indeterminism manifests as...

Ambiguity and ambiguity aversion have been widely studied in decision theory
and economics both at a theoretical and an experimental level. After Ellsberg's
seminal studies challenging subjective expected utility theory (SEUT), several
(mainly normative) approaches have been put forward to reproduce ambiguity
aversion and Ellsberg-type preferences....

A general tension-reduction (GTR) model was recently considered to derive
quantum probabilities as (universal) averages over all possible forms of
non-uniform fluctuations, and explain their considerable success in describing
experimental situations also outside of the domain of physics, for instance in
the ambit of quantum models of cognition and...

Fractals such as the Cantor set can be equipped with intrinsic arithmetic
operations (addition, subtraction, multiplication, division) that map the
fractal into itself. The arithmetics allows one to define calculus and algebra
intrinsic to the fractal in question, and one can formulate classical and
quantum physics within the fractal set. In partic...

The extended Bloch representation of quantum mechanics was recently derived
to offer a (hidden-measurement) solution to the measurement problem. In this
article we use it to investigate the geometry of superposition and entangled
states, explaining the interference effects, and the entanglement correlations,
in terms of the different orientations t...

We analyse in this paper the data collected in a set of experiments performed
on human subjects on the combination of natural concepts. We investigate the
mutual influence of conceptual conjunction and negation by measuring the
membership weights of a list of exemplars with respect to two concepts, e.g.,
'Fruits' and 'Vegetables', and their conjunc...

We provide an overview of the results we have attained in the last decade on
the identification of quantum structures in cognition and, more specifically,
in the formalization and representation of natural concepts. We firstly discuss
the quantum foundational reasons that led us to investigate the mechanisms of
formation and combination of concepts...

Entangled states are in conflict with the general physical principle saying
that a composite entity exists if and only if its components also exist, and
therefore are in pure states. To solve this paradox one has to complete the
standard formulation of quantum mechanics, by adding more pure states. We show
that this can be done, in a consistent way...

Traditional cognitive science rests on a foundation of classical logic and
probability theory. This foundation has been seriously challenged by several
findings in experimental psychology on human decision making. Meanwhile, the
formalism of quantum theory has provided an efficient resource for modeling
these classically problematical situations. I...

Increasing experimental evidence shows that humans combine concepts in a way
that violates the rules of classical logic and probability theory. On the other
hand, mathematical models inspired by the formalism of quantum theory are in
accordance with data on concepts and their combinations. In this paper, we
investigate a novel type of concept combi...