We investigate how femtoscopic correlations modify the relation between the spin entanglement of emitted particle pairs and that of pairs selected at a given relative momentum. For two spin- $\frac{1}{2}$ particles, we show that the momentum-selected spin state can be entangled even when the corresponding state at emission is separable. We derive a momentum-dependent separability criterion that determines whether the observed spin correlations require entanglement at emission. As an application, we consider a pair of identical $Λ$ hyperons, for which quantum statistics and final-state interactions affect the singlet and triplet spin channels differently at low relative momentum. Our results provide a framework for using experimentally accessible spin correlations to investigate entanglement at emission.We investigate how femtoscopic correlations modify the relation between the spin entanglement of emitted particle pairs and that of pairs selected at a given relative momentum. For two spin-$\frac{1}{2}$ particles, we show that the momentum-selected spin state can be entangled even when the corresponding state at emission is separable. We derive a momentum-dependent separability criterion that determines whether the observed spin correlations require entanglement at emission. As an application, we consider a pair of identical $Λ$ hyperons, for which quantum statistics and final-state interactions affect the singlet and triplet spin channels differently at low relative momentum. Our results provide a framework for using experimentally accessible spin correlations to investigate entanglement at emission.

nucl-thCross-listedarXiv:2610.14358Oct 13, 20260 citations

Global Dirac bispinor entanglement under Lorentz boosts

Victor A. S. V. Bittencourt, Alex E. Bernardini, Massimo Blasone A

The effects of Lorentz boosts on the quantum entanglement encoded by a pair of massive spin- $\frac{1}{2}$ particles are described according to the Lorentz covariant structure described by Dirac bispinors. The quantum system considered incorporates four degrees of freedom: two of them related to the bispinor intrinsic parity and the other two related to the bispinor spin projection, i.e., the Dirac particle helicity. Because of the natural multipartite structure involved, the Meyer-Wallach global measure of entanglement is preliminarily used for computing global quantum correlations, while the entanglement separately encoded by spin degrees of freedom is measured through the negativity of the reduced two-particle spin-spin state. A general framework to compute the changes on quantum entanglement induced by a boost is developed and then specialized to describe three particular antisymmetric two-particle states. According to the results obtained, two-particle spin-spin entanglement cannot be created by the action of a Lorentz boost in a spin-spin separable antisymmetric state. On the other hand, the maximal spin-spin entanglement encoded by antisymmetric superpositions is degraded by Lorentz boosts driven by high-speed frame transformations. Finally, the effects of boosts on chiral states are shown to exhibit interesting invariance properties, which can only be obtained through such a Lorentz covariant formulation of the problem.The effects of Lorentz boosts on the quantum entanglement encoded by a pair of massive spin-$\frac{1}{2}$ particles are described according to the Lorentz covariant structure described by Dirac bispinors. The quantum system considered incorporates four degrees of freedom: two of them related to the bispinor intrinsic parity and the other two related to the bispinor spin projection, i.e., the Dirac particle helicity. Because of the natural multipartite structure involved, the Meyer-Wallach global measure of entanglement is preliminarily used for computing global quantum correlations, while the entanglement separately encoded by spin degrees of freedom is measured through the negativity of the reduced two-particle spin-spin state. A general framework to compute the changes on quantum entanglement induced by a boost is developed and then specialized to describe three particular antisymmetric two-particle states. According to the results obtained, two-particle spin-spin entanglement cannot be created by the action of a Lorentz boost in a spin-spin separable antisymmetric state. On the other hand, the maximal spin-spin entanglement encoded by antisymmetric superpositions is degraded by Lorentz boosts driven by high-speed frame transformations. Finally, the effects of boosts on chiral states are shown to exhibit interesting invariance properties, which can only be obtained through such a Lorentz covariant formulation of the problem.

arXiv:1801.00758Physical Review AMar 13, 201825 citations

Entanglement in a spin-one spin chain

Guo‐Feng Zhang, Shu‐Shen Li

Solid State CommunicationsFeb 20, 200615 citations

Entanglement and Non-Separability in Quantum Mechanics

G. Costa

Springer eBooksJan 1, 20033 citations

Introduction Of Quantum Entanglement Measure Based On The Expectation Values Of Pauli Operators

Mahmood Zeheiry

In this paper, firstly considering that in separable states, the measurement of one particle has no effect on the measurement of the second particle, we show that Alice and Bob can find directions in which the results of their measurements on the spin of the particle are always maximized. In other words, the state of the particle is an eigenstate for the operator that is applied in that direction, so the sum of the spins of two particles can have a maximum value. We will argue that in entangled states, due to the effect of particle measurement results on each other, Alice and Bob cannot find the desired operators. Therefore, in such measurements, the total spin of the particles will always be less than the mentioned maximum. But we ask them to try and measure in directions that will get the most value. Because this value is maximum for separable states and minimum for fully entangled states, and for the rest of the states, it will be proportional to the degree of entanglement between the two maximum and minimum values, we set this parameter as We are calling it the "separability index". Then, based on this index, the measure of entanglement was introduced and extended to states with higher dimensions. In the end, examples of di-qubit states di-qutrit states, and di-qudit states were investigated and the efficiency of the measure was confirmed by the results of the examples. Considering that in this measure, the values of entanglement are calculated based on the expectation values and we can measure the expectation values in the experiment, we hope to be one step closer to the testability of the entanglement value.In this paper, firstly considering that in separable states, the measurement of one particle has no effect on the measurement of the second particle, we show that Alice and Bob can find directions in which the results of their measurements on the spin of the particle are always maximized. In other words, the state of the particle is an eigenstate for the operator that is applied in that direction, so the sum of the spins of two particles can have a maximum value. We will argue that in entangled states, due to the effect of particle measurement results on each other, Alice and Bob cannot find the desired operators. Therefore, in such measurements, the total spin of the particles will always be less than the mentioned maximum. But we ask them to try and measure in directions that will get the most value. Because this value is maximum for separable states and minimum for fully entangled states, and for the rest of the states, it will be proportional to the degree of entanglement between the two maximum and minimum values, we set this parameter as We are calling it the "separability index". Then, based on this index, the measure of entanglement was introduced and extended to states with higher dimensions. In the end, examples of di-qubit states di-qutrit states, and di-qudit states were investigated and the efficiency of the measure was confirmed by the results of the examples. Considering that in this measure, the values of entanglement are calculated based on the expectation values and we can measure the expectation values in the experiment, we hope to be one step closer to the testability of the entanglement value.

arXiv:2211.08981Nov 14, 20220 citations

We investigate how femtoscopic correlations modify the relation between the spin entanglement of emitted particle pairs and that of pairs selected at a given relative momentum. For two spin-

\frac{1}{2}

particles, we show that the momentum-selected spin state can be entangled even when the corresponding state at emission is separable. We derive a momentum-dependent separability criterion that determines whether the observed spin correlations require entanglement at emission. As an application, we consider a pair of identical

Λ

hyperons, for which quantum statistics and final-state interactions affect the singlet and triplet spin channels differently at low relative momentum. Our results provide a framework for using experimentally accessible spin correlations to investigate entanglement at emission.

The effects of Lorentz boosts on the quantum entanglement encoded by a pair of massive spin-

\frac{1}{2}

particles are described according to the Lorentz covariant structure described by Dirac bispinors. The quantum system considered incorporates four degrees of freedom: two of them related to the bispinor intrinsic parity and the other two related to the bispinor spin projection, i.e., the Dirac particle helicity. Because of the natural multipartite structure involved, the Meyer-Wallach global measure of entanglement is preliminarily used for computing global quantum correlations, while the entanglement separately encoded by spin degrees of freedom is measured through the negativity of the reduced two-particle spin-spin state. A general framework to compute the changes on quantum entanglement induced by a boost is developed and then specialized to describe three particular antisymmetric two-particle states. According to the results obtained, two-particle spin-spin entanglement cannot be created by the action of a Lorentz boost in a spin-spin separable antisymmetric state. On the other hand, the maximal spin-spin entanglement encoded by antisymmetric superpositions is degraded by Lorentz boosts driven by high-speed frame transformations. Finally, the effects of boosts on chiral states are shown to exhibit interesting invariance properties, which can only be obtained through such a Lorentz covariant formulation of the problem.