arXiv subjects

Reza Hamzehofi

Publications and source records attributed to Reza Hamzehofi.

4 recordsLinked to original sources

arXiv2026

Relativistic quantum teleportation protected by the anti-Unruh effect

The interaction of an accelerated observer with a quantum field can modify the entanglement and quantum information shared between observers, thereby affecting quantum communication in non-inertial frames. We formulate the standard teleportation protocol in a relativistic setting where Alice remains inertial while Rob undergoes uniform acceleration and is modeled as an Unruh-DeWitt detector locally coupled to a massive scalar field. The detector-field interaction initially leads to a loss of entanglement and quantum information shared between Alice and Rob. Remarkably, under acceleration, the anti-Unruh regime can reverse this degradation, leading to an increase in both the shared entanglement and the accessible quantum information. We further find that, in the anti-Unruh regime, the teleportation fidelity is independent of the local free-evolution time of Alice's and Rob's states. At high accelerations, the recovered entanglement and quantum information enhance the teleportation fidelity, which approaches unity under appropriate conditions. These results demonstrate that the anti-Unruh effect can protect and recover quantum entanglement and information in a non-inertial frame by reducing the detector's effective temperature and the associated decoherence.

quant-ph↗

arXiv2025

From vanishing pairwise entanglement to global separability:Entanglement structure and measures in the W subspace

The $W$ subspace is defined as the subspace of the $n$-qubit Hilbert space spanned by states containing at most one excitation. In this work, a separability criterion is established for pure and mixed states supported in this subspace: if all reduced two-qubit subsystems are separable, then the entire $n$-qubit state is necessarily separable. This result motivates the identification of the sum of two-tangles as an entanglement measure for pure states supported in the $W$ subspace. Furthermore, it is shown that the commonly used $\pi$-tangle becomes ineffective for the $n$-qubit $W$ state as the system size increases, and vanishes in the large-$n$ limit. To address this limitation, the sum of $\pi$-tangles is introduced, which, like the sum of two-tangles, successfully quantifies the entanglement of the $n$-qubit $W$ state in the large-$n$ limit. In addition, a new condition for entanglement measures is introduced, which facilitates the formulation of a well-behaved and physically meaningful entanglement measure.

quant-ph↗

arXiv2024

Entanglement measures for multipartite quantum systems:limitations and new approaches

In this research, we investigate the distribution of entanglement within two entangled $n$-qubit systems using the one-tangle and $\pi$-tangle. Our analysis reveals that for certain quantum states such as the generalized $W$ state, where the probability coefficients depend on the number of qubits, increasing the system size causes these traditional measures to gradually diminish, with the monogamy relation tending toward equality. This behavior highlights a limitation of conventional tangle-based measures in capturing multipartite correlations in large systems. To overcome this, we introduce two alternative measures: the sum of squared one-tangles and the generalized residual entanglement. Unlike the standard one-tangle and $\pi$-tangle, these new quantities remain robust as the number of qubits increases. Moreover, we propose a strong monogamy relation that preserves nontrivial entanglement distribution even in the large-$n$ limit. Our results provide a refined framework for quantifying entanglement in high-dimensional multipartite systems.

quant-ph↗

arXiv2024

Separability criterion for n-particle states

This research introduces the concept of the purity number, which represents the number of separable s-particle sub-states within an n-particle state ($s<n$ ). It establishes that, for any , achieving the maximum purity number is both a necessary and sufficient condition for the separability of n-particle pure states, and a necessary condition for the separability of n-particle mixed states. Subsequently, the study delves into the concept of entanglement rate in n-particle pure states. The entanglement rate of an n-particle pure state, in which all entangled sub-states are maximally entangled, can be considered as a measure of entanglement.

quant-ph↗