Coherent-information analysis of quantum channels in simple quantum systems

Abstract

The coherent information concept is used to analyze a variety of simple quantum systems. Coherent information was calculated for the information decay in a two-level atom in the presence of an external resonant field, for the information exchange between two coupled two-level atoms, and for the information transfer from a two-level atom to another atom and to a photon field. The coherent information is shown to be equal to zero for all full-measurement procedures, but it completely retains its original value for quantum duplication. Transmission of information from one open subsystem to another one in the entire closed system is analyzed to learn quantum information about the forbidden atomic transition via a dipole active transition of the same atom. It is argued that coherent information can be used effectively to quantify the information channels in physical systems where quantum coherence plays an important role.

No Thermalization without Correlations

“…where ⊙ is the substitution symbol defined, e.g., in [36]. The superoperator L rel accounts for system-bath couplings responsible for the friction termF fr in Eq.…”

Entangling quantum measurements and their properties

“…for R kl ≡ 1, we obtain the maximum possible value E = log 2 D of the entanglement due to the entangling measurement. The superoperator of the two-time channel A → M , i.e., a channel that links the initial state of the quantum system and final state of the apparatus, has the following form [30]:…”

Destruction of states in quantum mechanics

“…Note that D s Ω and D Ω are superoperators. In quantum information theory superoperators similar to D Ω are considered as choice superoperators describing the coherent information transfer between subsets of the entire system [5].…”