Density HypercubesHigher Order Interference and Hyper-Decoherence: a Categorical Approach (original) (raw)
Physica Scripta, 2014
Quantum probabilities differ from classical ones in many ways, e.g., by violating the well-known Bell and CHSH inequalities or another simple inequality due to R. Wright. The latter one has recently regained attention because of its equivalence to a novel noncontextual inequality by Klyachko et al. On the other hand, quantum probabilities still obey many limitations which need not hold any more in more general probabilistic theories (super quantum probabilities). Wright, Popescu and Rohrlich identified states which are included in such theories, but impossible in quantum mechanics, and they showed this using its Hilbert space formalism. Recently, Fritz et al. and Cabello detected that the impossibility of these states can be derived from very general principles (local orthogonality and global exclusive disjunction, respectively) without using Hilbert space techniques. In the paper, an alternative derivation from rather different phyisical principles will be presented. These are a reasonable calculus of conditional probability (i.e., a model for the quantum measurement process) and the absence of third-order interference. The concept of third-order interference was introduced by Sorkin who also recognized its impossibility in quantum mechanics.
On the ongoing experiments looking for higher-order interference: What are they really testing?
arXiv: Quantum Physics, 2016
The existence of higher than pairwise quantum interference in the set-up, in which there are more than two slits, is currently under experimental investigation. However, it is still unclear what the confirmation of existence of such interference would mean for quantum theory -- whether that usual quantum mechanics is merely a limiting case of some more general theory or whether that some assumption of quantum theory taken as a fundamental one does not actually hold true. The present paper tries to understand why quantum theory is limited only to a certain kind of interference.
Quasi-Quantization: Classical Statistical Theories with an Epistemic Restriction
Fundamental Theories of Physics, 2015
A significant part of quantum theory can be obtained from a single innovation relative to classical theories, namely, that there is a fundamental restriction on the sorts of statistical distributions over physical states that can be prepared. This is termed an "epistemic restriction" because it implies a fundamental limit on the amount of knowledge that any observer can have about the physical state of a classical system. This article provides an overview of epistricted theories, that is, theories that start from a classical statistical theory and apply an epistemic restriction. We consider both continuous and discrete degrees of freedom, and show that a particular epistemic restriction called classical complementarity provides the beginning of a unification of all known epistricted theories. This restriction appeals to the symplectic structure of the underlying classical theory and consequently can be applied to an arbitrary classical degree of freedom. As such, it can be considered as a kind of quasi-quantization scheme; "quasi" because it generally only yields a theory describing a subset of the preparations, transformations and measurements allowed in the full quantum theory for that degree of freedom, and because in some cases, such as for binary variables, it yields a theory that is a distortion of such a subset. Finally, we propose to classify quantum phenomena as weakly or strongly nonclassical by whether or not they can arise in an epistricted theory. Contents A. Quadrature quantum subtheories and the Stabilizer formalism 32 References 33
Towards the demystificatiom of quantum interference
2009
It has been shown that velocity of propagation of wave front cannot coincide with observable velocity of quantum particles. It is additional argument leads to conclusion that phase wave of de Broglie cannot be associated with single "elementary" particle like electron. Therefore quantum interference under linear superposition cannot describe energy distribution in extended quantum particles. Essentially new approach is required in order to establish non-linear relativistic wave equations with soliton-like solutions.
Ruling out Higher-Order Interference from Purity Principles
Entropy, 2017
As first noted by Rafael Sorkin, there is a limit to quantum interference. The interference pattern formed in a multi-slit experiment is a function of the interference patterns formed between pairs of slits; there are no genuinely new features resulting from considering three slits instead of two. Sorkin has introduced a hierarchy of mathematically conceivable higher-order interference behaviours, where classical theory lies at the first level of this hierarchy and quantum theory theory at the second. Informally, the order in this hierarchy corresponds to the number of slits on which the interference pattern has an irreducible dependence. Many authors have wondered why quantum interference is limited to the second level of this hierarchy. Does the existence of higher-order interference violate some natural physical principle that we believe should be fundamental? In the current work we show that such principles can be found which limit interference behaviour to second-order, or "quantum-like", interference, but that do not restrict us to the entire quantum formalism. We work within the operational framework of generalised probabilistic theories, and prove that any theory satisfying Causality, Purity Preservation, Pure Sharpness, and Purification-four principles that formalise the fundamental character of purity in nature-exhibits at most second-order interference. Hence these theories are, at least conceptually, very "close" to quantum theory. Along the way we show that systems in such theories correspond to Euclidean Jordan algebras. Hence, they are self-dual and, moreover, multi-slit experiments in such theories are described by pure projectors.
Quartic quantum theory: an extension of the standard quantum mechanics
Journal of Physics A: Mathematical and Theoretical, 2008
We propose an extended quantum theory, in which the number K of parameters necessary to characterize a quantum state behaves as fourth power of the number N of distinguishable states. As the simplex of classical N-point probability distributions can be embedded inside a higher dimensional convex body M Q N of mixed quantum states, one can further increase the dimensionality constructing the set of extended quantum states. The embedding proposed corresponds to an assumption that the physical system described in N dimensional Hilbert space is coupled with an auxiliary subsystem of the same dimensionality. The extended theory works for simple quantum systems and is shown to be a non-trivial generalisation of the standard quantum theory for which K = N 2. Imposing certain restrictions on initial conditions and dynamics allowed in the quartic theory one obtains quadratic theory as a special case. By imposing even stronger constraints one arrives at the classical theory, for which K = N .
Interference and entanglement: an intrinsic approach
Journal of Physics A: Mathematical and General, 2002
An addition rule of impure density operators, which provides a pure state density operator, is formulated. Quantum interference including visibility property is discussed in the context of the density operator formalism. A measure of entanglement is then introduced as the norm of the matrix equal to the difference between a bipartite density matrix and the tensor product of partial traces. Entanglement for arbitrary quantum observables for multipartite systems is discussed. Star-product kernels are used to map the formulation of the addition rule of density operators onto the addition rule of symbols of the operators. Entanglement and nonlocalization of the pure state projector and allied operators are discussed. Tomographic and Weyl symbols (tomograms and Wigner functions) are considered as examples. The squeezed-states and some spin-states (two qubits) are studied to illustrate the formalism.
Nonextensive approach to decoherence in quantum mechanics
Physics Letters A, 2001
We propose a nonextensive generalization (q parametrized) of the von Neumann equation for the density operator. Our model naturally leads to the phenomenon of decoherence, and unitary evolution is recovered in the limit of q → 1. The resulting evolution yields a nonexponential decay for quantum coherences, fact that might be attributed to nonextensivity. We discuss, as an example, the loss of coherence observed in trapped ions. 05.30.Ch, 03.65.Bz, 42.50.Lc In the past decade, there have been substantial advances regarding a nonextensive, q-parametrized generalization of Gibbs-Boltzmann statistical mechanics . The q parametrization is based on an approximate expression for the exponential, or the q-exponential
Electronic Proceedings in Theoretical Computer Science, 2015
We consider possible non-signaling composites of probabilistic models based on euclidean Jordan algebras. Subject to some reasonable constraints, we show that no such composite exists having the exceptional Jordan algebra as a direct summand. We then construct several dagger compact categories of such Jordan-algebraic models. One of these neatly unifies real, complex and quaternionic mixed-state quantum mechanics, with the exception of the quaternionic "bit". Another is similar, except in that (i) it excludes the quaternionic bit, and (ii) the composite of two complex quantum systems comes with an extra classical bit. In both of these categories, states are morphisms from systems to the tensor unit, which helps give the categorical structure a clear operational interpretation. A no-go result shows that the first of these categories, at least, cannot be extended to include spin factors other than the (real, complex, and quaternionic) quantum bits, while preserving the representation of states as morphisms. The same is true for attempts to extend the second category to even-dimensional spin-factors. Interesting phenomena exhibited by some composites in these categories include failure of local tomography, supermultiplicativity of the maximal number of mutually distinguishable states, and mixed states whose marginals are pure.
Why interference phenomena do not capture the essence of quantum theory
2021
Quantum interference phenomena are widely viewed as posing a challenge to the classical worldview. Feynman even went so far as to proclaim that they are the only mystery and the basic peculiarity of quantum mechanics. Many have also argued that such phenomena force us to accept a number of radical interpretational conclusions, including: that a photon is neither a particle nor a wave but rather a schizophrenic sort of entity that toggles between the two possibilities, that reality is observer-dependent, and that systems either do not have properties prior to measurements or else have properties that are subject to nonlocal or backwards-in-time causal influences. In this work, we show that such conclusions are not, in fact, forced on us by the phenomena. We do so by describing an alternative to quantum theory, a statistical theory of a classical discrete field (the ‘toy field theory’) that reproduces the relevant phenomenology of quantum interference while rejecting these radical int...
A Royal Road to Quantum Theory (or Thereabouts), Extended Abstract
Electronic Proceedings in Theoretical Computer Science, 2017
A representation of finite-dimensional probabilistic models in terms of formally real Jordan algebras is obtained, in a strikingly easy way, from simple assumptions. This provides a framework in which real, complex and quaternionic quantum mechanics can be treated on an equal footing, and allows some (but not too much) room for other alternatives. This is based on earlier work (arXiv:1206:2897), but the development here is further simplified, and also extended in several ways. I also discuss the possibilities for organizing probabilistic models, subject to the assumptions discussed here, into symmetric monoidal categories, showing that such a category will automatically have a dagger-compact structure. (Recent joint work with Howard Barnum and Matthew Graydon (arXiv:1507.06278) exhibits several categories of this kind.
A dynamical system model for interference effects and the two-slit experiment of quantum physics
Physics Letters A, 1992
Given two probability density functionsf~ and f2, a method is described for combining the densities in a physically meaningful way. The method involves the construction of underlying transformations r, and r2, and then forming a dynamical system from these two transformations referred to as a random transformation. The invariant (stationary) probability density function for the random transformation is the "combined" density off~ and f2. This method of combining probability density functions is used to model interference effects in physical systems. In particular, the dynamics of the two-slit experiment of quantum physics is modelled by an appropriate random transformation. Computer results are presented which qualitatively appear like experimental results. The notion of wave is not needed in the model.
Special Relativity (RT) has been incomplete vis a vis Quantum Theory (QT) since 1927. But completing RT in the light of QT is not as simple as postulating nonlocality and stochasticity as elements of reality; otherwise, RT would not still be in conflict with QT after a century. Also, I contend that QT is incomplete vis a vis RT. We show how to complete both theories and merge them into an embracive theory I call QR/TOPI. This theory offers a simpler avenue to integrate RT with QT than positing exotic causal structures like retrocausality, future input dependence, superdeterminism, etc. QR/TOPI provides the radical conceptual renewal wished by John Bell and, reciprocally, integrates Frame-Invariance into QT while at the same time, as demanded by 2022 Nobel laureate Anton Zeilinger, provides the (so far missing) basic physical meaning. The old outcast notion of absolute simultaneity is resurrected without any conflict with Einstein's relative simultaneity, while Frame-Invariance is preserved via our Quantumlike Transformation (QLT), which is an extension of the Lorentz Transformation (LT). QLT includes what LT excludes: nonlocality. Section 1 examines the philosophical foundations of Space and Time, focusing on RT, its plethora of empirical validations, and the tenets which make it incompatible with QT. Section 2 incorporates stochasticity into RT. Sections 3 through 5 gradually introduce QR/TOPI for multiple quanton systems, with full consideration of Bell Theorem, nonlocality, teleportation, and their implications. Section 6 attempts to review the current status quo. Section 7 makes the case for the incompleteness of RT and QT. Section 8 explains how to complete and integrate both theories so as to formally develop QR/TOPI. Finally, in Section 9, via multiple experimental setups, I zero in on Zeilinger's basic question: what does this really mean in a basic way?
Physical Review D, 2011
We link the recently discovered black hole-qubit correspondence to the structure of extra dimensions. In particular we show that for toroidal compactifications of type IIB string theory simple qubit systems arise naturally from the geometrical data of the tori parametrized by the moduli. We also generalize the recently suggested idea of the attractor mechanism as a distillation procedure of GHZ-like entangled states on the event horizon, to moduli stabilization for flux attractors in F-theory compactifications on elliptically fibered Calabi-Yau four-folds. Finally using a simple example we show that the natural arena for qubits to show up is an embedded one within the realm of fermionic entanglement of quantum systems with indistinguishable constituents.
Quantum Lightcone Fluctuations in Theories with Extra Dimensions
2000
The effects of small extra dimensions upon quantum fluctuations of the lightcone are examined. We argue that compactified extra dimensions modify the quantum fluctuations of gravitational field so as to induce lightcone fluctuations. This phenomenon can be viewed as being related to the Casimir effect. The observable manifestation of the lightcone fluctuations is broadening of spectral lines from distant sources.
Entanglement or separability: the choice of how to factorize the algebra of a density matrix
The European Physical Journal D, 2011
Quantum entanglement has become a resource for the fascinating developments in quantum information and quantum communication during the last decades. It quantifies a certain nonclassical correlation property of a density matrix representing the quantum state of a composite system. We discuss the concept of how entanglement changes with respect to different factorizations of the algebra which describes the total quantum system. Depending on the considered factorization a quantum state appears either entangled or separable. For pure states we always can switch unitarily between separability and entanglement, however, for mixed states a minimal amount of mixedness is needed. We discuss our general statements in detail for the familiar case of qubits, the GHZ states, Werner states and Gisin states, emphasizing their geometric features. As theorists we use and play with this free choice of factorization, which for an experimentalist is often naturally fixed. For theorists it offers an extension of the interpretations and is adequate to generalizations, as we point out in the examples of quantum teleportation and entanglement swapping.