The Mudcat Café TM
Thread #104378   Message #2723410
Posted By: Amos
14-Sep-09 - 11:34 AM
Thread Name: BS: Random Traces From All Over
Subject: RE: BS: Random Traces From All Over
Received 29 April 2009; revised 8 August 2009; published 8 September 2009

Quantum Darwinism recognizes that we—the observers—acquire our information about the "systems of interest" indirectly from their imprints on the environment. Here, we show that information about a system can be acquired from a mixed-state, or hazy, environment, but the storage capacity of an environment fragment is suppressed by its initial entropy. In the case of good decoherence, the mutual information between the system and the fragment is given solely by the fragment's entropy increase. For fairly mixed environments, this means a reduction by a factor 1-h, where h is the haziness of the environment, i.e., the initial entropy of an environment qubit. Thus, even such hazy environments eventually reveal the state of the system, although now the intercepted environment fragment must be larger by ~(1-h)-1 to gain the same information about the system.