ar X iv : q ua nt - p h / 04 03 17 4 v 2 2 7 Ju n 20 04 Quantum entanglement as information theoretic resource

We address the following criterion for quantifying the quantum information resources: classically simulable vs. classically non-simulable information processing. This approach gives rise to existence of a deeper level of quantum information processing–which we refer to as " quantum communication channel ". We particularly show, that following the recipes of the standard theory of entanglement measures does not necessarily give rise to unlocking the quantum communication channel, which is naturally quantified by Bell inequalities. 1 Introduction.-Quantum entanglement is recognized as a resource for useful quantum information/computation (henceforth: QIC) processing [1-6]. Consequently, quantifying entanglement is among the central issues of QIC theory. The standard theory of entanglement measures (cf., e.g., [1] for a review) offers the recipes for improving entanglement (and/or purity) of a quantum state (system) while bearing the following point as a background: " the system is more entangled if it allows for better performance of some task (impossible without entanglement) " [1]. However, it is natural (for many reasons) to expect that certain additional criteria/requirements concerning the state preparation/manipulation might improve the performance of some task. E.g. a more elaborate information theoretic analysis might shed some new light in this concern; particularly, the analysis devoted to the efficient (classically non-simulable) tasks is not yet fully developed in the standard theory [1]. To this end, it is useful to recall: distinguishing the classically non-simulable yet quantum mechanically achievable processing is probably the main motivation for developing QIC theory [7]. In this paper, we point out existence of the more fundamental information processing level that we refer to as " entanglement as information resource ". Actually, we move the focus of the task of quantifying entanglement to the following criterion/divide: classically simulable vs. classically non-simulable information processing. This new approach directly addresses the issue raised by Feynman [7] which is still un-resolved by the standard theory of entan-glement measures. With this, hopefully, we sharpen the issue of necessity of entanglement for the efficient (classically non-simulable) information processing. Finally, recognizing " entanglement as information resource " as the " quantum communication channel (QCC) " , we may phrase our main result as follows: manipulating entangled states according to the recipes of the standard theory does not necessarily imply opening (unlocking) QCC; in general, certain additional operations are required for opening QCC, which as a quantum information resource can be quantified by Bell-inequalities (henceforth: BI) [8, 9].