arXiv subjects

I. Sainz

Publications and source records attributed to I. Sainz.

4 recordsLinked to original sources

arXiv2021

Truncated Wigner approximation as a non-positive Kraus map

We show that the Truncated Wigner Approximation developed in the flat phase-space is mapped into a Lindblad-type evolution with an indefinite metric in the space of linear operators. As a result, the classically evolved Wigner function corresponds to a non-positive operator $\hat{R}(t)$, which does not describe a physical state. The rate of appearance of negative eigenvalues of $\hat{R}(t)$ can be efficiently estimated. The short-time dynamics of the Kerr and second harmonic generation Hamiltonains are discussed.

quant-ph↗

arXiv2020

Macroscopic approach to N-qudit systems

We develop a general scheme for an analysis of macroscopic qudit systems: a) introduce a set of collective observables, which characterizes the macroscopic properties of qudits in an optimal way; b) construct projected $\tilde{Q}$-functions for $N$ qudit systems, containing full macroscopic information; c) propose a collective tomographic protocol both for a general and symmetric $N$-qudit states. The example of $N$-qutrit is analyzed in details and compared to $N$-qubit case

quant-ph↗

arXiv2006

Effective resonant transitions in quantum optical systems: kinematic and dynamic resonances

We show that quantum optical systems preserving the total number of excitations admit a simple classification of possible resonant transitions (including effective), which can be classified by analizying the free Hamiltonian and the corresponding integrals of motion. Quantum systems not preserving the total number of excitations do not admit such a simple classification, so that an explicit form of the effective Hamiltonian is needed to specify the allowed resonances. The structure of the resonant transitions essentially depends on the algebraic propereties of interacting subsystems.

quant-ph↗

arXiv2005

Qubits entanglement dynamics modified by an effective atomic environment

We study entanglement dynamics of a couple of two-level atoms resonantly interacting with a cavity mode and embedded in a dispersive atomic environment. We show that in the absence of the environment the entanglement reaches its maximum value when only one exitation is involved. Then, we find that the atomic environment modifies that entanglement dynamics and induces a typical collapse-revival structure even for an initial one photon Fock state of the field.

quant-ph↗