© 2026 Aqora Quantum S.A.S.

Terms Privacy Legal Notice

Communications in Theoretical Physics

Nonlocality and Multipartite Entanglement in Asymptotically Flat Space-Times

Shahpoor Moradi, Firouz Amiri

Published Jan 1, 2016• 4 citations

Abstract

Abstract We study the Bell's inequality and multipartite entanglement generation for initially maximally entangled states of free Dirac field in a non inertial frame and asymptotically flat Robertson–Walker space-time. For two qubit case, we show that the Bell's inequality always is violated as measured by the accelerated observers which are in the causally connected regions. On the other hand, for those observers in the causally disconnected regions inequality is not violated for any values of acceleration. The generated three qubit state from two qubit state due to acceleration of one parties has a zero 3-tangle. For a three qubit state, the inequality violated for measurements done by both causally connected and disconnected observers. Initially GHZ state with non zero 3-tangle, in accelerated frame, transformed to a four qubit state with vanishing 4-tangle value. On the other hand, for a W-state with zero 3-tangle, in non inertial frame, transformed to a four qubit state with a non-zero 4-tangle acceleration dependent. In an expanding space-time with asymptotically flat regions, for an initially maximally entangled state, the maximum value of violation of Bell's inequality in the far past decreased in the far future due to cosmological particle creation. For some initially maximally entangled states, the generated four qubit state due to expansion of space-time, has non vanishing 4-tangle.

DOI: 10.1088/0253-6102/65/1/17

Related papers

Multipartite entanglement versus nonlocality for two families of N − qubit states

Sanchit Srivastava, Shohini Ghose

Entangled states of multiple qubits can violate Bell-type inequalities indicating nonlocal behavior of multiqubit quantum correlations. We analyze the relation between multipartite entanglement and genuine multipartite nonlocality, characterized by Svetlichny inequality violations, for two families of N − qubit states. We show that for the generalized Greenberger-Horne-Zeilinger family of states, Svetlichny inequality is not violated when the n − tangle is less than 1 / 2 for any even number of qubits. On the other hand, the maximal slice states always violate the Svetlichny inequality when n − tangle is nonzero, and the violation increases monotonically with tangle. Our work generalizes the relations between tangle and Svetlichny inequality violations previously derived for three qubits.

arXiv:2409.10888•Physical Review Research•Sep 9, 2025•0 citations

Restriction on the local realism violation in three-qubit states and its relation with tripartite entanglement

Artur Barasiński

Quantum entanglement and non-locality are two special aspects of quantum correlations. The relationship between multipartite entanglement and non-locality is at the root of the foundations of quantum mechanics but there is still no general quantitative theory. In order to address this issue we analyze the relationship between tripartite non-locality and tripartite entanglement measure, called the three-tangle. We describe the states which give the extremal quantum values of a Bell-type inequality for a given value of the tripartite entanglement. Moreover, we show that such extremal states can be reached if one introduced an appropriate order induced by the three-π entanglement measure. Finally, we derive an analytical expression relating tripartite entanglement to the maximal violations of the Bell-type inequalities.

Scientific Reports•Aug 13, 2018•5 citations

Multipartite entanglement of fermionic system in accelerated frames

Meng Shi, Hai-Mei Zhong, Zhu‐Jun Zheng

We investigate the entanglement measures of tripartite W-State and GHZ-state in noninertial frame through the coordinate transformation between Minkowski and Rindler. First it is shown that all three qubits undergo in a uniform acceleration $a$ of W-State, we find that the one-tangle, two-tangle, and $π$-tangle decrease when the acceleration parameter $r$ increases, and the two-tangle cannot arrive to infinity of the acceleration. Next we show that the one qubit goes in a uniform acceleration $a_{1}$ and the other two undergo in a uniform acceleration $a$ of GHZ-state, we find that the two-tangle is equal to zero and $N_{B_I (A_I C_I)} = N_{C_I (A_I B_I)}\neq N_{A_I (B_I C_I)}$, but one-tangle and $π$-tangle never reduce to zero for any acceleration.

arXiv:1906.07267•May 27, 2019•1 citation

Towards an equivalence between maximal entanglement and maximal quantum nonlocality

Victoria Lipińska, Florian J. Curchod, Alejandro Máttar +1 more

While all bipartite pure entangled states are known to generate correlations violating a Bell inequality, and are therefore nonlocal, the quantitative relation between pure state entanglement and nonlocality is poorly understood. In fact, some Bell inequalities are maximally violated by non-maximally entangled states and this phenomenon is also observed for other operational measures of nonlocality. In this work, we study a recently proposed measure of nonlocality defined as the probability that a pure state displays nonlocal correlations when subjected to random measurements. We first prove that this measure satisfies some natural properties for an operational measure of nonlocality. Then, we show that for pure states of two qubits the measure is monotonic with entanglement for all correlation two-outcome Bell inequalities: for all these inequalities, the more the state is entangled, the larger the probability to violate them when random measurements are performed. Finally, we extend our results to the multipartite setting.

arXiv:1802.09982•New Journal of Physics•Jun 4, 2018•28 citations

Maximally entangled states and Bell's inequality in relativistic regime

Shahpoor Moradi

In this Letter we show that in relativistic regime maximally entangled state of two spin-1/2 particles not only gives maximal violation of the Bell-CHSH inequality but also gives the largest violation attainable for any pairs of four spin observables that are noncommuting for both systems. Also we extend our results to three spin-1/2 particles. We obtain the largest eigenvalue of Bell operator and show that this value is equal to expectation value of Bell operator on GHZ state.

arXiv:1201.0512•Jan 2, 2012•0 citations

Quantum entanglement and coherence of tripartite W state for Dirac fields under noisy channels in non-inertial frames

Kwang-Il Kim, Myong Chol Pak, Ok Song An +3 more

Abstract We investigate quantum entanglement and coherence of tripartite W state for Dirac fields under phase damping, phase flip and bit flip channels, respectively, in non-inertial frames. Via π -tangle, we numerically compute tripartite entanglement of W state under three channels when two observers are accelerated. We also analytically derive l 1 -norm quantum coherence of W state under the simultaneous influence of Unruh effect and noisy environments. For phase-damping and phase-flip channels, both the acceleration and noisy channels modulate the behaviour of the tripartitle entanglement and quantum coherence. They do not vanish even for infinite acceleration when only A 's qubit is under noisy environment, in contrast with the case when two or more observers’ qubits are under noisy environment. In the case of the bit flip channel, the behavior of the tripartite entanglement is similar to the one of the phase flip channel, but quantum coherence remains unaffected by the environment.

Physica Scripta•May 20, 2022•8 citations

Abstract We study the Bell's inequality and multipartite entanglement generation for initially maximally entangled states of free Dirac field in a non inertial frame and asymptotically flat Robertson–Walker space-time. For two qubit case, we show that the Bell's inequality always is violated as measured by the accelerated observers which are in the causally connected regions. On the other hand, for those observers in the causally disconnected regions inequality is not violated for any values of acceleration. The generated three qubit state from two qubit state due to acceleration of one parties has a zero 3-tangle. For a three qubit state, the inequality violated for measurements done by both causally connected and disconnected observers. Initially GHZ state with non zero 3-tangle, in accelerated frame, transformed to a four qubit state with vanishing 4-tangle value. On the other hand, for a W-state with zero 3-tangle, in non inertial frame, transformed to a four qubit state with a non-zero 4-tangle acceleration dependent. In an expanding space-time with asymptotically flat regions, for an initially maximally entangled state, the maximum value of violation of Bell's inequality in the far past decreased in the far future due to cosmological particle creation. For some initially maximally entangled states, the generated four qubit state due to expansion of space-time, has non vanishing 4-tangle.

Entangled states of multiple qubits can violate Bell-type inequalities indicating nonlocal behavior of multiqubit quantum correlations. We analyze the relation between multipartite entanglement and genuine multipartite nonlocality, characterized by Svetlichny inequality violations, for two families of N − qubit states. We show that for the generalized Greenberger-Horne-Zeilinger family of states, Svetlichny inequality is not violated when the n − tangle is less than 1 / 2 for any even number of qubits. On the other hand, the maximal slice states always violate the Svetlichny inequality when n − tangle is nonzero, and the violation increases monotonically with tangle. Our work generalizes the relations between tangle and Svetlichny inequality violations previously derived for three qubits.

Quantum entanglement and non-locality are two special aspects of quantum correlations. The relationship between multipartite entanglement and non-locality is at the root of the foundations of quantum mechanics but there is still no general quantitative theory. In order to address this issue we analyze the relationship between tripartite non-locality and tripartite entanglement measure, called the three-tangle. We describe the states which give the extremal quantum values of a Bell-type inequality for a given value of the tripartite entanglement. Moreover, we show that such extremal states can be reached if one introduced an appropriate order induced by the three-π entanglement measure. Finally, we derive an analytical expression relating tripartite entanglement to the maximal violations of the Bell-type inequalities.

We investigate the entanglement measures of tripartite W-State and GHZ-state in noninertial frame through the coordinate transformation between Minkowski and Rindler. First it is shown that all three qubits undergo in a uniform acceleration

a

of W-State, we find that the one-tangle, two-tangle, and

π

-tangle decrease when the acceleration parameter

r

increases, and the two-tangle cannot arrive to infinity of the acceleration. Next we show that the one qubit goes in a uniform acceleration

a_{1}

and the other two undergo in a uniform acceleration

a

of GHZ-state, we find that the two-tangle is equal to zero and

a

, but one-tangle and

π

-tangle never reduce to zero for any acceleration.

While all bipartite pure entangled states are known to generate correlations violating a Bell inequality, and are therefore nonlocal, the quantitative relation between pure state entanglement and nonlocality is poorly understood. In fact, some Bell inequalities are maximally violated by non-maximally entangled states and this phenomenon is also observed for other operational measures of nonlocality. In this work, we study a recently proposed measure of nonlocality defined as the probability that a pure state displays nonlocal correlations when subjected to random measurements. We first prove that this measure satisfies some natural properties for an operational measure of nonlocality. Then, we show that for pure states of two qubits the measure is monotonic with entanglement for all correlation two-outcome Bell inequalities: for all these inequalities, the more the state is entangled, the larger the probability to violate them when random measurements are performed. Finally, we extend our results to the multipartite setting.

Abstract We investigate quantum entanglement and coherence of tripartite W state for Dirac fields under phase damping, phase flip and bit flip channels, respectively, in non-inertial frames. Via π -tangle, we numerically compute tripartite entanglement of W state under three channels when two observers are accelerated. We also analytically derive l 1 -norm quantum coherence of W state under the simultaneous influence of Unruh effect and noisy environments. For phase-damping and phase-flip channels, both the acceleration and noisy channels modulate the behaviour of the tripartitle entanglement and quantum coherence. They do not vanish even for infinite acceleration when only A 's qubit is under noisy environment, in contrast with the case when two or more observers’ qubits are under noisy environment. In the case of the bit flip channel, the behavior of the tripartite entanglement is similar to the one of the phase flip channel, but quantum coherence remains unaffected by the environment.