Speed of evolution in entangled fermionic systems

We consider the simplest identical-fermion system that exhibits the phenomenon of entanglement (beyond exchange correlations) to analyze its speed of evolution towards an orthogonal state, and revisit the relation between this latter and the amount of fermionic entanglement. A characterization of the quantum speed limit and the orthogonality times is performed, throwing light into the general structure of the faster and the slower states. Such characterization holds not only for fermionic composites, but apply more generally to a wide family of 6-dimensional states, irrespective of the specific nature of the system. Further, it is shown that the connection between speed of evolution and entanglement in the fermionic system, though more subtle than in composites of distinguishable parties, may indeed manifest for certain classes of states

Dynamics of closed quantum systems under stochastic resetting

We consider a closed quantum system subject to a stochastic resetting process. The generic expression for the resulting density operator is formulated for arbitrary resetting dynamics, fully characterised by the distribution of times between consecutive reset events. We analyse the behaviour of the state in the long-time regime, as well as the evolution of relevant quantities in the study of quantum coherence and closed- vs open-system dynamics. Our general results are complemented with examples involving paradigmatic resetting distributions, and special attention is paid to the two-level (qubit) system, in which we elucidate the effects of the renewal process on the speed of evolution toward an orthogonal state, and gain insight into the resetting applied to open systems.Comment: An analysis of closed quantum system subject to arbitrary stochastic resetting process is carried ou

Sudden death of entanglement in fermionic systems under collective decoherence

We analyze the dynamics of entanglement due to decoherence in asystem of two identical fermions with spin 3/2 interacting with a global bosonicenvironment. We make use of an appropriate measure of the so-called fermionicentanglement to quantify the fermionic correlations, and compare the dynamicaleffects due to decoherence with those that arise in a pair of distinguishablequbits immersed in the same environment. According to the system?s initialstate, three types of qualitatively different dynamics are identified: i) invariantregime, corresponding to initial states that belong to a decoherence free subspace(DFS), which maintain invariant their entanglement and coherence throughoutthe evolution; ii) exponential decay, corresponding to initial states orthogonal tothe DFS, and evolve towards states whose entanglement and coherence decreaseexponentially; iii) entanglement sudden death, corresponding to initial states that havesome overlap with the DFS and exhibit a richer dynamics leading, in particular,to the sudden death of the fermionic entanglement, while the coherence decaysexponentially. Our analysis offers insights into the dynamics of entanglementin open systems of identical particles and into the existence of decoherence freesubspaces and entanglement sudden death in indistinguishable-fermion systems.Fil: Bussandri, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Majtey, Ana Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Valdés Hernández, Andrea. Universidad Nacional Autónoma de México; Méxic

The underlying order induced by orthogonality and the quantum speed limit

We perform a comprehensive analysis of the set of parameters $\{r_{i}\}$ that provide the energy distribution of pure qutrits that evolve towards a distinguishable state at a finite time $\tau$, when evolving under an arbitrary and time-independent Hamiltonian. The orthogonality condition is exactly solved, revealing a non-trivial interrelation between $\tau$ and the energy spectrum and allowing the classification of $\{r_{i}\}$ into families organized in a 2-simplex, $\delta^{2}$. Furthermore, the states determined by $\{r_{i}\}$ are likewise analyzed according to their quantum-speed limit. Namely, we construct a map that distinguishes those $r_{i}$s in $\delta^{2}$ correspondent to states whose orthogonality time is limited by the Mandelstam--Tamm bound from those restricted by the Margolus--Levitin one. Our results offer a complete characterization of the physical quantities that become relevant in both the preparation and study of the dynamics of three-level states evolving towards orthogonality.Comment: orthogonality time; quantum speed limit; three-level systems; dynamics towards orthogonalit