Using the Wigner function in phase space, we study quantum steering and entanglement between two coupled harmonic oscillators. We derive expressions for purity and quantum steering in both directions and identify several important selection rules. Our results extend the work reported in {\color{blue} [Phys. Rev. E 97, 042203 (2018)]} focused on the weak coupling regime, revealing significant deviations in the ultra-strong coupling regime. In particular, Makarov's prediction of a separable ground state contrasts with our exact calculations, highlighting the limitations of his approach under strong coupling conditions. We show that quantum steering between excited oscillators is completely absent even in the ultra-strong coupling regime. Similarly, resonant oscillators have no steering, and ground states cannot steer any receiver state. We find that quantum steering becomes notably more pronounced as the system approaches resonance and within specific ranges of ultra-strong coupling. This behavior is marked by a clear asymmetry, where steering is present in only one direction, highlighting the delicate balance of interaction strengths that govern the emergence of quantum correlations. These results advance our understanding of how excitation levels and coupling strengths influence quantum steering and entanglement in coupled harmonic oscillators.Using the Wigner function in phase space, we study quantum steering and entanglement between two coupled harmonic oscillators. We derive expressions for purity and quantum steering in both directions and identify several important selection rules. Our results extend the work reported in {\color{blue} [Phys. Rev. E 97, 042203 (2018)]} focused on the weak coupling regime, revealing significant deviations in the ultra-strong coupling regime. In particular, Makarov's prediction of a separable ground state contrasts with our exact calculations, highlighting the limitations of his approach under strong coupling conditions. We show that quantum steering between excited oscillators is completely absent even in the ultra-strong coupling regime. Similarly, resonant oscillators have no steering, and ground states cannot steer any receiver state. We find that quantum steering becomes notably more pronounced as the system approaches resonance and within specific ranges of ultra-strong coupling. This behavior is marked by a clear asymmetry, where steering is present in only one direction, highlighting the delicate balance of interaction strengths that govern the emergence of quantum correlations. These results advance our understanding of how excitation levels and coupling strengths influence quantum steering and entanglement in coupled harmonic oscillators.

arXiv:2411.07010Nov 11, 20240 citations

Entanglement in three coupled harmonic oscillators

Abdeldjalil Merdaci, Ahmed Jellal

arXiv:1909.01997Physics Letters ANov 19, 201915 citations

Entanglement dynamics in coupled harmonic oscillators

Nicolás Quesada

Jan 1, 20110 citations

Einstein-Podolsky-Rosen Steering in Three Coupled Harmonic Oscillators

Ayoub Ghaba, Radouan Hab Arrih, Elhoussine Atmani +1 more

Quantum steering is one of the most intriguing phenomena in quantum mechanics and is essential for understanding correlations in multi-body systems. Despite its importance, analytical results for coupled three-body oscillators remain scarce. In this work, we investigate this phenomenon through a geometrical diagonalization approach, which reduces the degrees of freedom associated with the system's steering properties. Specifically, we derive analytical expressions for quantum steering in all possible directions using the Wigner function framework, as it provides a complete description of the system's quantum state. Our results indicate that excitations significantly enhance quantum steering across the system; this stands in contrast to the ground state $(0,0,0)$ , which exhibits no steerable correlations. Furthermore, both the directionality and topology of these correlations are governed by the spatial distribution of the excitations rather than their magnitude. We also observe symmetric steering behavior between oscillators $x$ , $y$ , and $z$ under equivalent excitation conditions, which can be formalized as $S^{(n,m,l)}_{x\to z}(θ)=S^{(n,m,l)}_{x\to y}(-θ),\quad S^{(n,m,l)}_{z\to x}(θ)=S^{(n,m,l)}_{y\to x}(-θ)$ , and $S^{(n,m,l)}_{y\to z}(θ)=S^{(n,m,l)}_{z\to y}(-θ)$ . Therefore, we elucidate how excitation levels and mixing angles generate and enhance steering in three coupled harmonic oscillators.Quantum steering is one of the most intriguing phenomena in quantum mechanics and is essential for understanding correlations in multi-body systems. Despite its importance, analytical results for coupled three-body oscillators remain scarce. In this work, we investigate this phenomenon through a geometrical diagonalization approach, which reduces the degrees of freedom associated with the system's steering properties. Specifically, we derive analytical expressions for quantum steering in all possible directions using the Wigner function framework, as it provides a complete description of the system's quantum state. Our results indicate that excitations significantly enhance quantum steering across the system; this stands in contrast to the ground state $(0,0,0)$, which exhibits no steerable correlations. Furthermore, both the directionality and topology of these correlations are governed by the spatial distribution of the excitations rather than their magnitude. We also observe symmetric steering behavior between oscillators $x$, $y$, and $z$ under equivalent excitation conditions, which can be formalized as $S^{(n,m,l)}_{x\to z}(θ)=S^{(n,m,l)}_{x\to y}(-θ),\quad S^{(n,m,l)}_{z\to x}(θ)=S^{(n,m,l)}_{y\to x}(-θ)$, and $S^{(n,m,l)}_{y\to z}(θ)=S^{(n,m,l)}_{z\to y}(-θ)$. Therefore, we elucidate how excitation levels and mixing angles generate and enhance steering in three coupled harmonic oscillators.

quant-pharXiv:2601.01307Jan 6, 20260 citations

Decoherence of Einstein–Podolsky–Rosen steering

L. Rosales-Zárate, Run Yan Teh, Simon Kiesewetter +3 more

We consider two systems A and B that share Einstein–Podolsky–Rosen (EPR) steering correlations and study how these correlations will decay when each of the systems is independently coupled to a reservoir. EPR steering is a directional form of entanglement, and the measure of steering can change depending on whether system A is steered by B, or vice versa. First, we examine the decay of the steering correlations of the two-mode squeezed state. We find that if system B is coupled to a reservoir, then the decoherence of the steering of A by B is particularly marked, to the extent that there is a sudden death of steering after a finite time. We find a different directional effect if the reservoirs are thermally excited. Second, we study the decoherence of the steering of a Schrödinger cat state, modeled as the entangled state of a spin and harmonic oscillator, when the macroscopic system (the cat) is coupled to a reservoir.We consider two systems A and B that share Einstein–Podolsky–Rosen (EPR) steering correlations and study how these correlations will decay when each of the systems is independently coupled to a reservoir. EPR steering is a directional form of entanglement, and the measure of steering can change depending on whether system A is steered by B, or vice versa. First, we examine the decay of the steering correlations of the two-mode squeezed state. We find that if system B is coupled to a reservoir, then the decoherence of the steering of A by B is particularly marked, to the extent that there is a sudden death of steering after a finite time. We find a different directional effect if the reservoirs are thermally excited. Second, we study the decoherence of the steering of a Schrödinger cat state, modeled as the entangled state of a spin and harmonic oscillator, when the macroscopic system (the cat) is coupled to a reservoir.

arXiv:1508.06383Journal of the Optical Society of America BApr 1, 201558 citations

(0,0,0)

, which exhibits no steerable correlations. Furthermore, both the directionality and topology of these correlations are governed by the spatial distribution of the excitations rather than their magnitude. We also observe symmetric steering behavior between oscillators

x

y

, and

z

under equivalent excitation conditions, which can be formalized as

S^{(n,m,l)}_{x\to z}(θ)=S^{(n,m,l)}_{x\to y}(-θ),\quad S^{(n,m,l)}_{z\to x}(θ)=S^{(n,m,l)}_{y\to x}(-θ)

, and

S^{(n,m,l)}_{y\to z}(θ)=S^{(n,m,l)}_{z\to y}(-θ)

. Therefore, we elucidate how excitation levels and mixing angles generate and enhance steering in three coupled harmonic oscillators.