Evgenii Glushkov

Deriving Entropic Inequalities for Two Coupled Superconducting Circuits

  1. Evgenii Glushkov,
  2. Anastasiia Glushkova,
  3. and V.I. Man'ko
We discuss the known construction of two interacting superconducting circuits, based on Josephson junctions, that can be precisely engineered and easily controlled. In particular, we
use the parametric excitation of two circuits, realized by an instant change of the qubit coupling, to study entropic and information properties of the density matrix of the composite system. The density matrix is obtained from the initial thermal state and is then analyzed in the approximation of small perturbation parameter and sufficiently low temperature. We also check the subadditivity condition for this system both for von Neumann and deformed entropies and look at the dependance of mutual information on the temperature of the system. Finally, we discuss the applicability of this approach to describe such system of two coupled superconducting qubits as harmonic oscillators with limited Hilbert space.
arxiv pdf

On Testing Entropic Inequalities for Superconducting Qudit

  1. Evgenii Glushkov,
  2. Anastasiia Glushkova,
  3. and V.I. Man'ko
The aim of this work is to verify the new entropic and information inequalities for non-composite systems using experimental 5×5 density matrix of the qudit state, measured by the
tomographic method in a multi-level superconducting circuit. These inequalities are well-known for bipartite and tripartite systems, but have never been tested for superconducting qudits. Entropic inequalities can also be used to evaluate the accuracy of experimental data and the value of mutual information, deduced from them, may charachterize correlations between different degrees of freedom in a noncomposite system.
arxiv pdf