scholarly journals Entanglement of Pseudo-Hermitian Random States

Entropy ◽  
2020 ◽  
Vol 22 (10) ◽  
pp. 1109
Author(s):  
Cleverson Andrade Goulart ◽  
Mauricio Porto Pato
Keyword(s):  
Density Matrix ◽  
Random Matrices ◽  
Bell States ◽  
Von Neumann Entropy ◽  
Abstract Model ◽  
Von Neumann ◽  
Fock States ◽  
Bosonic System ◽  
Random States

In a recent paper (A. Fring and T. Frith, Phys. Rev A 100, 101102 (2019)), a Dyson scheme to deal with density matrix of non-Hermitian Hamiltonians has been used to investigate the entanglement of states of a PT-symmetric bosonic system. They found that von Neumann entropy can show a different behavior in the broken and unbroken regime. We show that their results can be recast in terms of an abstract model of pseudo-Hermitian random matrices. It is found however that although the formalism is practically the same, the entanglement is not of Fock states but of Bell states.

scholarly journals ENTANGLEMENT ENTROPY: HELICITY VERSUS SPIN

2008 ◽  
Vol 06 (01) ◽  
pp. 181-186 ◽  
Author(s):  
SONG HE ◽  
SHUXIN SHAO ◽  
HONGBAO ZHANG
Keyword(s):  
Density Matrix ◽  
Entanglement Entropy ◽  
Specific Form ◽  
Von Neumann Entropy ◽  
Particle State ◽  
Inertial Reference Frame ◽  
Helicity State ◽  
Von Neumann ◽  
Left Handed ◽  
Massive Spin

For a massive spin 1/2 field, we present the reduced spin and helicity density matrix, respectively, for the same pure one particle state. Their relation has also been developed. Furthermore, we calculate and compare the corresponding entanglement entropy for spin and helicity within the same inertial reference frame. Due to the distinct dependence on momentum degree of freedom between spin and helicity states, the resultant helicity entropy is different from that of spin in general. In particular, we find that both helicity entanglement for a spin eigenstate and spin entanglement for a right handed or left handed helicity state do not vanish, and their Von Neumann entropy has no dependence on the specific form of momentum distribution, as long as it is isotropic.

scholarly journals WIGNER ROTATIONS, BELL STATES, AND LORENTZ INVARIANCE OF ENTANGLEMENT AND VON NEUMANN ENTROPY

2004 ◽  
Vol 02 (02) ◽  
pp. 183-200 ◽  
Author(s):  
CHOPIN SOO ◽  
CYRUS C. Y. LIN
Keyword(s):  
Lorentz Invariance ◽  
Zeta Functions ◽  
Bell States ◽  
Von Neumann Entropy ◽  
Lorentz Transformations ◽  
Von Neumann ◽  
Infinite Dimensional ◽  
Einstein Podolsky Rosen ◽  
Definition Of ◽  
Reduced Density

We compute, for massive particles, the explicit Wigner rotations of one-particle states for arbitrary Lorentz transformations; and the explicit Hermitian generators of the infinite-dimensional unitary representation. For a pair of spin 1/2 particles, Einstein–Podolsky–Rosen–ell entangled states and their behaviour under the Lorentz group are analyzed in the context of quantum field theory. Group theoretical considerations suggest a convenient definition of the Bell states which is slightly different from the conventional assignment. The behaviour of Bell states under arbitrary Lorentz transformations can then be described succinctly. Reduced density matrices applicable to systems of identical particles are defined through Yang's prescription. The von Neumann entropy of each of the reduced density matrix is Lorentz invariant; and its relevance as a measure of entanglement is discussed, and illustrated with an explicit example. A regularization of the entropy in terms of generalized zeta functions is also suggested.

scholarly journals Monotonicity of the von Neumann Entropy Expressed as a Function of Rényi Entropies

2014 ◽  
Vol 21 (03) ◽  
pp. 1450006 ◽  
Author(s):  
Mark Fannes
Keyword(s):  
Density Matrix ◽  
Von Neumann Entropy ◽  
Von Neumann ◽  
Integer Order ◽  
Odd Order ◽  
Rényi Entropies ◽  
Even Order ◽  
Renyi Entropies

The von Neumann entropy of a density matrix of dimension d, expressed in terms of the first d − 1 integer order Rényi entropies, is monotonically increasing in Rényi entropies of even order and decreasing in those of odd order.

scholarly journals ENTANGLEMENT IN VALENCE-BOND-SOLID STATES

2010 ◽  
Vol 24 (11) ◽  
pp. 1361-1440 ◽  
Author(s):  
VLADIMIR E. KOREPIN ◽  
YING XU
Keyword(s):  
Density Matrix ◽  
Condensed Matter ◽  
Valence Bond ◽  
Von Neumann Entropy ◽  
Information Measurement ◽  
Von Neumann ◽  
Solid States ◽  
The Subject ◽  
Definition Of ◽  
Valence Bond Solid

This article reviews the quantum entanglement in Valence-Bond-Solid (VBS) states defined on a lattice or a graph. The subject is presented in a self-contained and pedagogical way. The VBS state was first introduced in the celebrated paper by I. Affleck, T. Kennedy, E. H. Lieb and H. Tasaki (abbreviation AKLT is widely used). It became essential in condensed matter physics and quantum information (measurement-based quantum computation). Many publications have been devoted to the subject. Recently entanglement was studied in the VBS state. In this review, we start with the definition of a general AKLT spin chain and the construction of VBS ground state. In order to study entanglement, a block subsystem is introduced and described by the density matrix. Density matrices of 1-dimensional models are diagonalized and the entanglement entropies (the von Neumann entropy and Rényi entropy) are calculated. In the large block limit, the entropies also approach finite limits. Study of the spectrum of the density matrix led to the discovery that the density matrix is proportional to a projector.

Density matrix and purity evolution in dissipative two-level systems: I. Theory and path integral results for tunneling dynamics

2021 ◽  
Vol 23 (9) ◽  
pp. 5113-5124
Author(s):  
Sambarta Chatterjee ◽  
Nancy Makri
Keyword(s):  
Density Matrix ◽  
Path Integral ◽  
Von Neumann Entropy ◽  
Level System ◽  
Von Neumann ◽  
Bacteriochlorophyll Dimer ◽  
Two Level Systems ◽  
Tunneling Dynamics ◽  
Reduced Density ◽  
Harmonic Bath

The time evolution of the purity (the trace of the square of the reduced density matrix) and von Neumann entropy in a symmetric two-level system coupled to a dissipative harmonic bath is investigated through analytical arguments and accurate path integral calculations on simple models and the singly excited bacteriochlorophyll dimer.

scholarly journals Many-Body Systems and Quantum Chaos: The Multiparticle Quantum Arnol’d Cat

2019 ◽  
Vol 4 (3) ◽  
pp. 72
Author(s):  
Giorgio Mantica
Keyword(s):  
Hamiltonian System ◽  
Density Matrix ◽  
Quantum Chaos ◽  
Reduced Density Matrix ◽  
Von Neumann Entropy ◽  
Physical Parameters ◽  
Many Body ◽  
Von Neumann ◽  
Many Body Systems ◽  
Reduced Density

A multi-particle extension of the Arnol’d cat Hamiltonian system is presented, which can serve as a fully dynamical model of decoherence. The behavior of the von Neumann entropy of the reduced density matrix is studied, in time and as a function of the physical parameters, with special regard to increasing the mass of the cat particle.

scholarly journals Large deviation bounds for k -designs

2009 ◽  
Vol 465 (2111) ◽  
pp. 3289-3308 ◽  
Author(s):  
Richard A. Low
Keyword(s):  
Haar Measure ◽  
Random Distribution ◽  
Large Deviation ◽  
Von Neumann Entropy ◽  
General Technique ◽  
Von Neumann ◽  
Canonical State ◽  
Random States ◽  
The Universe ◽  
Random State

We present a technique for de-randomizing large deviation bounds of functions on the unitary group. We replace the Haar measure with a pseudo-random distribution, a k -design. k -Designs have the first k moments equal to those of the Haar measure. The advantage of this is that (approximate) k -designs can be implemented efficiently, whereas Haar random unitaries cannot. We find large deviation bounds for unitaries chosen from a k -design and then illustrate this general technique with three applications. We first show that the von Neumann entropy of a pseudo-random state is almost maximal. Then we show that, if the dynamics of the universe produces a k -design, then suitably sized subsystems will be in the canonical state, as predicted by statistical mechanics. Finally we show that pseudo-random states are useless for measurement-based quantum computation.

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