Abstract Using the Moshinsky model, we analyze the spatial correlation and the entanglement of the ground state across different bipartitions of a system composed by N pairs of harmonically confined fermions of two different interacting species. We find that in the strongly attractive regime fermions tend to localize within a confined region, while Pauli exclusion induces a spatial repulsion among identical particles. Conversely, in the strongly repulsive regime, the system exhibits phase separation into two spatially distinct domains. We propose a suitably designed entanglement measure that takes into account the (in)distinguishable nature of the particles, so as to guarantee that only quantum correlations beyond exchange or Slater correlations contribute to the entanglement. Our findings reveal how entanglement varies across different bipartitions, influenced by both the number of pairs and the interaction strength. The obtained entanglement between distinguishable species increases with both N and the interaction strength, whereas the entanglement between subsystems of which at least one contains particles of both species decreases with N, suggesting a screening effect that weakens effective interactions among parties of the same kind. Our results sheds light on the intricate interplay between particle statistics and entanglement dynamics in composite quantum systems, and provides insights into the fundamental quantum correlations in fermionic systems.
Abstract Using the Moshinsky model, we analyze the spatial correlation and the entanglement of the ground state across different bipartitions of a system composed by N pairs of harmonically confined fermions of two different interacting species. We find that in the strongly attractive regime fermions tend to localize within a confined region, while Pauli exclusion induces a spatial repulsion among identical particles. Conversely, in the strongly repulsive regime, the system exhibits phase separation into two spatially distinct domains. We propose a suitably designed entanglement measure that takes into account the (in)distinguishable nature of the particles, so as to guarantee that only quantum correlations beyond exchange or Slater correlations contribute to the entanglement. Our findings reveal how entanglement varies across different bipartitions, influenced by both the number of pairs and the interaction strength. The obtained entanglement between distinguishable species increases with both N and the interaction strength, whereas the entanglement between subsystems of which at least one contains particles of both species decreases with N, suggesting a screening effect that weakens effective interactions among parties of the same kind. Our results sheds light on the intricate interplay between particle statistics and entanglement dynamics in composite quantum systems, and provides insights into the fundamental quantum correlations in fermionic systems.
The fermionization regime and entanglement correlations of two distinguishable harmonically confined fermions interacting via a zero-range potential is addressed. We present two alternative representations of the ground state that we associate with two different types of one-dimensional spaces. These spaces, in turn, induce different correlations between particles and thus require a suitable definition of entanglement. We find that the entanglement of the ground state is strongly conditioned by those one-dimensional space features. We also find that in the strongly attractive regime the relative ground state is a highly localized state leading to maximum entanglement. Our analysis shows that in the strongly repulsive regime the ground state changes smoothly from a superposition of Slater-like states to a finite superposition of Slaters, this lack of accessible states yields to Pauli blocking as a strong signature of fermionization. Our results indicate that entangled states could be obtained in current experiments by reaching the non-interacting regime from the interacting regime. Entangled states could also be obtained when a state is brought from the interacting regime into the strongly repulsive regime by changing the scattering length near the confinement-induced resonance. Finally, we show that the first excited state obtained in the absence of interactions and the third excited fermionized state are maximally entangled.
Abstract The fermionization regime and entanglement correlations of two distinguishable harmonically confined fermions interacting via a zero-range potential is addressed. We present two alternative representations of the ground state that we associate with two different types of one-dimensional spaces. These spaces, in turn, induce different correlations between particles and thus require a suitable definition of entanglement. We find that the entanglement of the ground state is strongly conditioned by those one-dimensional space features. We also find that in the strongly attractive regime the relative ground state is a highly localized state leading to maximum entanglement. Our analysis shows that in the strongly repulsive regime the ground state changes smoothly from a superposition of Slater-like states to a finite superposition of Slaters, this lack of accessible states yields to Pauli blocking as a strong signature of fermionization. Our results indicate that entangled states could be obtained in current experiments by reaching the non-interacting regime from the interacting regime. Entangled states could also be obtained when a state is brought from the interacting regime into the strongly repulsive regime by changing the scattering length near the confinement-induced resonance (CIR). Finally, we show that the first excited state obtained in the absence of interactions and the third excited fermionized state are maximally entangled.
The ground-state entanglement of a single particle of the N-harmonium system (i.e., a completely-integrable model of N particles where both the confinement and the two-particle interaction are harmonic) is shown to be analytically determined in terms of N and the relative interaction strength. For bosons, we compute the von Neumann entropy of the one-body reduced density matrix by using the corresponding natural occupation numbers. There exists a critical number Nc of particles so that below it, for positive values of the coupling constant, the entanglement grows when the number of particles is increasing; the opposite occurs for N>Nc. For fermions, we compute the one-body reduced density matrix for the closed-shell spinned case. In the strong coupling regime, the linear entropy of the system decreases when N is growing. For fixed N, the entanglement is found (a) to decrease (increase) for negatively (positively) increasing values of the coupling constant, and (b) to grow when the energy is increasing. Moreover, the spatial and spin contributions to the total entanglement are found to be of comparable size.
We study the momentum distributions and spatial correlations of few harmonically confined SU(N) fermions using quantum Monte Carlo methods. In our study, we vary the spin degeneracy N from 2 to 6 and the total number of particles from 6 to 18. Only balanced mixtures, with the same number of atoms per spin type, and repulsive unlike-spin contact interactions are considered. Going from N=2 to N=6, with the same occupancy of each spin state, we observe an increase of atom-atom correlations. This effect is particularly significant in the momentum distributions, which show fatter tails at large k ($k\ensuremath{\sigma}\phantom{\rule{0.16em}{0ex}}>\phantom{\rule{0.16em}{0ex}}5, \ensuremath{\sigma}$ being the oscillator length) when N grows, in agreement with experimental findings. Those tails also show the expected ${k}^{\ensuremath{-}4}$ decay related to the Tan contact for different values of the spin degeneracy. According to our results, the local spin ordering and the spin-spin correlations are mainly determined by N via the Pauli exclusion principle, with minor influences from the particle-particle interactions, irrespective of the total number of confined atoms.
The entanglement of the N-harmonium system (i.e., a completely-integrable model of N particles where both the confinement and the two-particle interaction are har-monic) is shown to be analytically determined in terms of N and the relative interaction strength. First, the entanglement of the N-boson system via the von Neumann entropy is computed by use of the corresponding natural occupation numbers. Below a critical value Nc of N it is found that, for positive values of the coupling constant the entan-glement grows when the number of particles is increasing; opposite situation occurs for N> Nc. Then the entanglement of the N-fermion system is investigated by means of the linear entropy, which is a linearized form of the von Neumann entropy of the one-body reduced density matrix. We have shown that the entanglement grows when the number of particles is increasing in the region of negative coupling. For positively increasing values of the coupling the entanglement as a function of N varies according to various regimes. Moreover, in the strong coupling regime the entropy of the system decreases when N is growing. For fixed N, the entanglement is found (a) to decrease (increase) for negatively (positively) increasing values of the coupling constant, and (b) to grow when the energy is increasing. Finally, let us point out that the spatial and spin contributions to the total entanglement are of comparable size.
Quantum entanglement in systems of identical particles is often obscured by the interplay between exchange-induced correlations and the operational framework used to define entanglement. To study the role of exchange statistics, we propose a scheme using two \textit{distinguishable} particles where an exchange symmetry is artificially engineered via a relative phase θ in the initial state. This approach allows continuous tuning from bosonic (θ=0) to fermionic (θ=π) statistics. By monitoring the interplay between purity and coherence, we uncover distinct dynamical regimes dictated by the interaction strength U and the phase θ. For particles initially loaded in a bound state, strong U suppresses coherence development by avoiding the scattering band, reducing the purity toward its minimum. For particles initially on neighboring sites, coherence grows linearly in time. While non-symmetric inputs feature a sharp purity reduction at intermediate U, due to the competition between bound and unbound states, symmetric initial conditions produce transient coherence bursts that significantly enhance the purity. More generally, tuning the phase θ reveals a high-purity region over a range of θ at intermediate interactions, with the purity collapsing to 1/2 as θ approaches the fermionic limit. Our results show that the imposed statistics, or lack thereof, reshapes the entanglement dynamics and its response to the interaction U.