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 approximately (1-h)(-1) to gain the same information about the system.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 approximately (1-h)(-1) to gain the same information about the system.

arXiv:0904.0418Physical Review LettersSep 8, 200992 citations

Quantum Darwinism and non-Markovian dissipative dynamics from quantum phases of the spin-1/2 XX model

Gian Luca Giorgi, Fernando Galve, Roberta Zambrini

Quantum Darwinism explains the emergence of a classical description of objects in terms of the creation of many redundant registers in an environment containing their classical information. This amplification phenomenon, where only classical information reaches the macroscopic observer and through which different observers can agree on the objective existence of such object, has been revived lately for several types of situations, successfully explaining classicality. We explore quantum Darwinism in the setting of an environment made of two level systems which are initially prepared in the ground state of the $\mathit{XX}$ model, which exhibits different phases; we find that the different phases have different abilities to redundantly acquire classical information about the system, the ``ferromagnetic phase'' being the only one able to complete quantum Darwinism. At the same time we relate this ability to how non-Markovian the system dynamics is, based on the interpretation that non-Markovian dynamics is associated with backflow of information from environment to system, thus spoiling the information transfer needed for Darwinism. Finally, we explore mixing of bath registers by allowing a small interaction among them, finding that this spoils the stored information as previously found in the literature.Quantum Darwinism explains the emergence of a classical description of objects in terms of the creation of many redundant registers in an environment containing their classical information. This amplification phenomenon, where only classical information reaches the macroscopic observer and through which different observers can agree on the objective existence of such object, has been revived lately for several types of situations, successfully explaining classicality. We explore quantum Darwinism in the setting of an environment made of two level systems which are initially prepared in the ground state of the $\mathit{XX}$ model, which exhibits different phases; we find that the different phases have different abilities to redundantly acquire classical information about the system, the ``ferromagnetic phase'' being the only one able to complete quantum Darwinism. At the same time we relate this ability to how non-Markovian the system dynamics is, based on the interpretation that non-Markovian dynamics is associated with backflow of information from environment to system, thus spoiling the information transfer needed for Darwinism. Finally, we explore mixing of bath registers by allowing a small interaction among them, finding that this spoils the stored information as previously found in the literature.

arXiv:1504.02105Physical Review AAug 7, 201535 citations

Darwinism in quantum systems?

Azhar Iqbal, A. H. Toor

arXiv:quant-ph/0103085Physics Letters AMar 1, 200225 citations

Blurred quantum Darwinism across quantum reference frames

Thao P. Le, Piotr Mironowicz, Paweł Horodecki

Quantum Darwinism describes objectivity of quantum systems via their correlations with their environment---information that hypothetical observers can recover by measuring the environments. However, observations are done with respect to a frame of reference. Here we take the formalism of [Giacomini et al., Nat. Commun. 10, 494 (2019)] and consider the repercussions on objectivity when changing quantum reference frames. We find that objectivity depends on nondegenerative relative separations, conditional state localization, and environment macrofractions. There is different objective information in different reference frames due to the interchangeability of entanglement and coherence, and of statistical mixing and classical correlations. As such, objectivity is subjective across quantum reference frames.Quantum Darwinism describes objectivity of quantum systems via their correlations with their environment---information that hypothetical observers can recover by measuring the environments. However, observations are done with respect to a frame of reference. Here we take the formalism of [Giacomini et al., Nat. Commun. 10, 494 (2019)] and consider the repercussions on objectivity when changing quantum reference frames. We find that objectivity depends on nondegenerative relative separations, conditional state localization, and environment macrofractions. There is different objective information in different reference frames due to the interchangeability of entanglement and coherence, and of statistical mixing and classical correlations. As such, objectivity is subjective across quantum reference frames.

arXiv:2006.06364Physical Review ADec 22, 20207 citations

\mathit{XX}

model, which exhibits different phases; we find that the different phases have different abilities to redundantly acquire classical information about the system, the ``ferromagnetic phase'' being the only one able to complete quantum Darwinism. At the same time we relate this ability to how non-Markovian the system dynamics is, based on the interpretation that non-Markovian dynamics is associated with backflow of information from environment to system, thus spoiling the information transfer needed for Darwinism. Finally, we explore mixing of bath registers by allowing a small interaction among them, finding that this spoils the stored information as previously found in the literature.