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The properties of the Shannon entropy are not violated in quantum measurements

PierGianLuca Porta Mana

Published Feb 6, 2003• 1 citation
OpenAlex

Abstract

Brukner and Zeilinger [Phys. Rev. A 63 (2001) 022113] have claimed that two properties of the Shannon conditional entropy are violated in quantum experiments. It is shown here that the analysis by which they support their claim is flawed by the fact that they mix (probabilities and) entropies relative to different contexts, i.e., different experimental arrangements. It is also argued that the context-dependency of the Shannon entropy has nothing to do with the quantum or classical nature of experiments.

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Consistency of the Shannon entropy in quantum experiments

PierGianLuca Porta Mana

The consistency of the Shannon entropy, when applied to outcomes of quantum experiments, is analysed. It is shown that the Shannon entropy is fully consistent and its properties are never violated in quantum settings, but attention must be paid to logical and experimental contexts. This last remark is shown to apply regardless of the quantum or classical nature of the experiments.

arXiv:quant-ph/0302049•Physical Review A•Jun 21, 2004•21 citations

On the Supposed Conceptual Inadequacy of the Shannon Information

Christopher G. Timpson

In Phys. Rev. A 63 022113 (2001), Brukner and Zeilinger claim that the Shannon information is not well defined as a measure of information in quantum mechanics, adducing arguments that seek to show that it is inextricably tied to classical notions of measurement. It is shown here that these arguments do not succeed: the Shannon information does not have problematic ties to classical concepts. In a further argument, Brukner and Zeilinger compare the Shannon information unfavourably to their preferred information measure, I(p), with regard to the definition of a notion of `total information content'. This argument is found unconvincing and the relationship betwen measures of information and notions of `total information content' investigated.

•Dec 30, 2001•8 citations

Comment on "Conceptual Inadequacy of Shannon Information ..." by C. Brukner and A. Zeilinger

Michael J. W. Hall

It is pointed out that the case for Shannon entropy and von Neumann entropy, as measures of uncertainty in quantum mechanics, is not as bleak as suggested in quant-ph/0006087. The main argument of the latter is based on one particular interpretation of Shannon's H-function (related to consecutive measurements), and is shown explicitly to fail for other physical interpretations. Further, it is shown that Shannon and von Neumann entropies have in fact a common fundamental significance, connected to the existence of a unique geometric measure of uncertainty for classical and quantum ensembles. Some new properties of the ``total information'' measure proposed in quant-ph/0006087 are also given.

arXiv:quant-ph/0007116•Jul 31, 2000•8 citations

BELL'S INEQUALITY AND CONTEXTUAL INFORMATION

Feryal Safinejad, Afshin Shafiee, Reza Maleeh

The properties of the Shannon entropy (concavity and strong additivity) are satisfied in both classical and quantum experiments, if the context of experiment is considered appropriately. We show that these properties hold true in a classical model with the feature of being contextual, where a correlation is observed between events. Our results show that the classical example is similar to an entangled singlet state for spin-½ particles. But, contrary to general opinion, [Formula: see text] is not a necessary and sufficient condition for violating Bell's inequality, since it has been obtained on the basis of a common cause pattern. In other words, it is possible to reconstruct the amount of information contained in a quantum entangled state according to the common cause criterion satisfying local realism.

International Journal of Quantum Information•Aug 1, 2006•0 citations

Entropy and information causality in general probabilistic theories

Howard Barnum, Jonathan Barrett, Lisa Orloff Clark +5 more

We investigate the concept of entropy in probabilistic theories more general than quantum mechanics, with particular reference to the notion of information causality (IC) recently proposed by Pawlowski et al (2009 arXiv:0905.2292). We consider two entropic quantities, which we term measurement and mixing entropy. In the context of classical and quantum theory, these coincide, being given by the Shannon and von Neumann entropies, respectively; in general, however, they are very different. In particular, while measurement entropy is easily seen to be concave, mixing entropy need not be. In fact, as we show, mixing entropy is not concave whenever the state space is a non-simplicial polytope. Thus, the condition that measurement and mixing entropies coincide is a strong constraint on possible theories. We call theories with this property monoentropic . Measurement entropy is subadditive, but not in general strongly subadditive. Equivalently, if we define the mutual information between two systems A and B by the usual formula I ( A : B )= H ( A )+ H ( B )- H ( AB ), where H denotes the measurement entropy and AB is a non-signaling composite of A and B , then it can happen that I ( A : BC )< I ( A : B ). This is relevant to IC in the sense of Pawlowski et al : we show that any monoentropic non-signaling theory in which measurement entropy is strongly subadditive, and also satisfies a version of the Holevo bound, is informationally causal, and on the other hand we observe that Popescu–Rohrlich boxes, which violate IC, also violate strong subadditivity. We also explore the interplay between measurement and mixing entropy and various natural conditions on theories that arise in quantum axiomatics.

arXiv:0909.5075•New Journal of Physics•Mar 15, 2010•135 citations

The Applicability of Shannon Information in Quantum Mechanics and Zeilinger's Foundational Principle

Christopher G. Timpson

Recently, Brukner and Zeilinger have presented a number of arguments suggesting that the Shannon information is not well defined as a measure of information in quantum mechanics. If established, this result would be highly significant, as the Shannon information is fundamental to the way we think about information not only in classical but also in quantum information theory. On consideration, however, these arguments are found unsuccessful; I go on to suggest how they might be arising as a consequence of Zeilinger's proposed foundational principle for quantum mechanics.

Philosophy of Science•Dec 1, 2003•11 citations
Brukner and Zeilinger [Phys. Rev. A 63 (2001) 022113] have claimed that two properties of the Shannon conditional entropy are violated in quantum experiments. It is shown here that the analysis by which they support their claim is flawed by the fact that they mix (probabilities and) entropies relative to different contexts, i.e., different experimental arrangements. It is also argued that the context-dependency of the Shannon entropy has nothing to do with the quantum or classical nature of experiments.
In Phys. Rev. A 63 022113 (2001), Brukner and Zeilinger claim that the Shannon information is not well defined as a measure of information in quantum mechanics, adducing arguments that seek to show that it is inextricably tied to classical notions of measurement. It is shown here that these arguments do not succeed: the Shannon information does not have problematic ties to classical concepts. In a further argument, Brukner and Zeilinger compare the Shannon information unfavourably to their preferred information measure, I(p), with regard to the definition of a notion of `total information content'. This argument is found unconvincing and the relationship betwen measures of information and notions of `total information content' investigated.
It is pointed out that the case for Shannon entropy and von Neumann entropy, as measures of uncertainty in quantum mechanics, is not as bleak as suggested in quant-ph/0006087. The main argument of the latter is based on one particular interpretation of Shannon's H-function (related to consecutive measurements), and is shown explicitly to fail for other physical interpretations. Further, it is shown that Shannon and von Neumann entropies have in fact a common fundamental significance, connected to the existence of a unique geometric measure of uncertainty for classical and quantum ensembles. Some new properties of the ``total information'' measure proposed in quant-ph/0006087 are also given.
The properties of the Shannon entropy (concavity and strong additivity) are satisfied in both classical and quantum experiments, if the context of experiment is considered appropriately. We show that these properties hold true in a classical model with the feature of being contextual, where a correlation is observed between events. Our results show that the classical example is similar to an entangled singlet state for spin-½ particles. But, contrary to general opinion, [Formula: see text] is not a necessary and sufficient condition for violating Bell's inequality, since it has been obtained on the basis of a common cause pattern. In other words, it is possible to reconstruct the amount of information contained in a quantum entangled state according to the common cause criterion satisfying local realism.
We investigate the concept of entropy in probabilistic theories more general than quantum mechanics, with particular reference to the notion of information causality (IC) recently proposed by Pawlowski et al (2009 arXiv:0905.2292). We consider two entropic quantities, which we term measurement and mixing entropy. In the context of classical and quantum theory, these coincide, being given by the Shannon and von Neumann entropies, respectively; in general, however, they are very different. In particular, while measurement entropy is easily seen to be concave, mixing entropy need not be. In fact, as we show, mixing entropy is not concave whenever the state space is a non-simplicial polytope. Thus, the condition that measurement and mixing entropies coincide is a strong constraint on possible theories. We call theories with this property monoentropic . Measurement entropy is subadditive, but not in general strongly subadditive. Equivalently, if we define the mutual information between two systems A and B by the usual formula I ( A : B )= H ( A )+ H ( B )- H ( AB ), where H denotes the measurement entropy and AB is a non-signaling composite of A and B , then it can happen that I ( A : BC )< I ( A : B ). This is relevant to IC in the sense of Pawlowski et al : we show that any monoentropic non-signaling theory in which measurement entropy is strongly subadditive, and also satisfies a version of the Holevo bound, is informationally causal, and on the other hand we observe that Popescu–Rohrlich boxes, which violate IC, also violate strong subadditivity. We also explore the interplay between measurement and mixing entropy and various natural conditions on theories that arise in quantum axiomatics.
Recently, Brukner and Zeilinger have presented a number of arguments suggesting that the Shannon information is not well defined as a measure of information in quantum mechanics. If established, this result would be highly significant, as the Shannon information is fundamental to the way we think about information not only in classical but also in quantum information theory. On consideration, however, these arguments are found unsuccessful; I go on to suggest how they might be arising as a consequence of Zeilinger's proposed foundational principle for quantum mechanics.