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arXiv:1403.6419 · Journal of Physics A Mathematical and Theoretical

Quantum entanglement as an aspect of pure spinor geometry

Vasileios I. Kiosses

Published Sep 18, 2014• 5 citations
arXivHTMLPDF

Abstract

Relying on the mathematical analogy of the pure states of a two-qubit system with four-component Dirac spinors, we provide an alternative consideration of quantum entanglement using the mathematical formulation of Cartanʼs pure spinors. A result of our analysis is that the Cartan equation of a two-qubit state is entanglement sensitive in the same way that the Dirac equation for fermions is mass sensitive. The Cartan equation for unentangled qubits is reduced to a pair of Cartan equations for single qubits as the Dirac equation for massless fermions separates into two Weyl equations. Finally, we establish a correspondence between the separability condition in qubit geometry and the separability condition in spinor geometry.

DOI
10.1088/1751-8113/47/40/405301

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Relying on the mathematical analogy of the pure states of a two-qubit system with four-component Dirac spinors, we provide an alternative consideration of quantum entanglement using the mathematical formulation of Cartanʼs pure spinors. A result of our analysis is that the Cartan equation of a two-qubit state is entanglement sensitive in the same way that the Dirac equation for fermions is mass sensitive. The Cartan equation for unentangled qubits is reduced to a pair of Cartan equations for single qubits as the Dirac equation for massless fermions separates into two Weyl equations. Finally, we establish a correspondence between the separability condition in qubit geometry and the separability condition in spinor geometry.
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We give a fermionic Fock space description of embedded entangled qubits. Within this framework the problem of classification of pure state entanglement boils down to the problem of classifying spinors. The usual notion of separable states turns out to be just a special case of the one of pure spinors. By using the notion of single, double and mixed occupancy representation with intertwiners relating them a natural physical interpretation of embedded qubits is found. As an application of these ideas one can make a physical sound meaning of some of the direct sum structures showing up in the context of the so-called black-hole/qubit correspondence. We discuss how the usual invariants for qubits serving as measures of entanglement can be obtained from invariants for spinors in an elegant manner. In particular a detailed case study for recovering the invariants for four-qubits within a spinorial framework is presented. We also observe that reality conditions on complex spinors defining Majorana spinors for embedded qubits boil down to self-conjugate states under the Wootters spin flip operation. Finally we conduct a study on the explicit structure of Spin(16,C)\text{Spin}(16,\mathbb{C})Spin(16,C) invariant polynomials related to the structure of possible measures of entanglement for fermionic systems with eight modes. Here we find an algebraically independent generating set of the generalized stochastic local operations and classical communication invariants and calculate their restriction to the dense orbit. We point out the special role the largest exceptional group E8{E}_{8}E8​ is playing in these considerations.
The four-vector formalism is commonly used in Minkowski spacetime, but there exists an alternative formalism with spinors. We revisit the spinor formalism in the context of quantum information and establish an unexpected connection between directions in light cones and the notion of entanglement. This allows us to interpret that timelike directions correspond to entangled states of two imaginary qubits, whereas null directions correspond to separable states. With the correspondence, the speed of a particle can be expressed in terms of the amount of entanglement in concurrence. Furthermore, the entanglement also leads to a novel interpretation of the fact that moving clocks run slowly.
The study of the entanglement properties of systems of N fermions has attracted considerable interest during the last few years. Various separability criteria for pure states of N identical fermions have been recently discussed but, except for the case of two-fermions systems, these criteria are difficult to implement and are of limited value from the practical point of view. Here we advance simple necessary and sufficient separability criteria for pure states of N identical fermions. We found that to be identified as separable, a state has to comply with one single identity involving either the purity or the von Neumann entropy of the single-particle reduced density matrix. These criteria, based on the verification of only one identity, are drastically simpler than the criteria discussed in the recent literature. We also derive two inequalities verified, respectively, by the purity and the entropy of the single-particle, reduced density matrix, which lead to natural entanglement measures for N -fermion pure states. Our present considerations are related to some classical results from the Hartree-Fock theory, which are here discussed from a different point of view in order to clarify some important points concerning the separability of fermionic pure states.
Abstract This chapter gives a detailed overview of entanglement for pure and mixed states. We begin with the Schmidt-decomposition theorem, which allows us to associate the subsystem mixedness of pure state with entanglement. We discuss the purification of mixed quantum states, the convexity of the set of separable states, and entanglement as a form of correlation. As an example we examine the Bloch decomposition for two qubits. For the detection of entanglement the Peres-Horodecki criterion is introduced, before we analyse the relation between entanglement and non-locality via the CHSH-Operator Criterion and the family of Werner states. We further consider Tsirelson’s bound and hidden non-locality. We then discuss important mathematical tools for entanglement detection, including the positive-map theorem, the Størmer-Woronowicz theorem, and the reduction criterion. In this context we examine the family of isotropic states. Finally, the Weyl states provide an example for which we study the geometry of two-qubit entanglement
In quantum mechanics (QM), the electron of spin-charge in probabilistic distribution about a nucleus of a hydrogen atom is described by non-relativistic Schrödinger’s wave equation. Its transformation to Dirac fermion of a complex four-component spinor is incorporated into relativistic quantum field theory (QFT). The quantum system in both cases is represented by a wave function but how it collapses to a point at observation omits out both the hidden variables of the spinor and their evolutionary paths into space-time. This presents an ontological dilemma that cannot be satisfactorily explained by conventional theories either driven by experiments or vice versa. In this study, the ontology of Dirac fermion within a proposed MP model of 4D quantum space-time of hydrogen atom type is examined. The electron of a point-particle and its transformation to Dirac fermion appears consistent with Dirac belt trick for the generation of superposition states of spin-charge and their antimatter. Center of mass reference frame relevant to Newtonian gravity is assigned to the spherical point-boundary of the model. This offers an intricate dynamic tool compatible with basic aspects of both QM and QFT. Some of these are explored for non-relativistic wave function and its collapse, quantized Hamiltonian, Dirac spinors, Weyl spinors, Majorana fermions and Lorentz transformation. How the model could further relate to space-time geometry for a body-mass in an elliptical orbit is plotted from an alternative interpretation of general relativity and a multiverse of the MP models at a hierarchy of scales is proposed for further considerations.