Average Entropy of a Quantum Subsystem

Average entropy of a subsystem.

If a quantum system of Hilbert space dimension mn is in a random pure state, the average entropy of a subsystem of dimension m ≤ n is conjectured to be S m,n = mn k=n+1 1 k − m−1 2n and is shown to be ≃ ln m − m 2n for 1 ≪ m ≤ n. Thus there is less than one-half unit of information, on average, in the smaller subsystem of a total system in a random pure state.

Coherent Control of Quantum Entropy via Quantum Interference in a Four-Level Atomic System

The time evaluation of quantum entropy in a four-level double- type atomic system is theoretically investigated. Quantum entanglement of the atom and its spontaneous emission fields is then discussed via quantum entropy. It is found that the degree of entanglement can be increased by the quantum interference induced by spontaneous emission. The phase dependence of the atom-field entanglement is...

Subsystem Entropy Exceeding Bekenstein's Bound *

If Bekenstein's conjectured bound on the microcanonical entropy, S ≤ 2πER, is applied to a closed subsystem of maximal linear size R and excitation energy up through E, it can be violated by an arbitrarily large factor by a scalar field having a symmetric potential allowing domain walls, and by the electromagnetic field modes in a coaxial cable.

coherent control of quantum entropy via quantum interference in a four-level atomic system

the time evaluation of quantum entropy in a four-level double- type atomic system is theoretically investigated. quantum entanglement of the atom and its spontaneous emission fields is then discussed via quantum entropy. it is found that the degree of entanglement can be increased by the quantum interference induced by spontaneous emission. the phase dependence of the atom-field entanglement is...

Subsystem Quantum Chemistry for Nanostructures