Forget the Entanglement; Here’s Quantum Error Correction Without It
Quantum error correction assisted quantum metrology without entanglement
Excerpts and salient points ~
+ Quantum information science has gained prominence as an area of research in the recent decades. One of the key promises of the field is that the the quantum regime contains intrinsic advantages over classical theories that can be exploited for a variety of informational tasks. A promising area of study which has gained considerable attention recently is the application of quantum error correction techniques to enhance the precision of quantum metrology. Quantum metrology concerns itself with the precise estimation of some unknown physical parameter, but the precision of such tools often require the preparation of non-classical quantum states that are sensitive to decoherence effects. Quantum error correction thus offers the promise of enhancing precision by reducing the amount of noise acting on the system.
+ Another key concern in quantum information is the study of the differences between quantum and classical theories, leading to the development of a theory of quantum resources. Examples of quantum resources include entanglement and quantum coherence. Quantum entanglement is at present a well established quantum resource with many applications such as cryptography, teleportation and super dense coding. In comparison, the resource theory of quantum coherence is a recent theoretical development, with applications in topics as diverse as quantum macroscopicity, quantum optics and quantum metrology. It is worth nothing that entanglement and coherence are not entirely separate quantum resources, since entangled states generally contains coherence, though the converse is not necessarily true.
+ In this article, we will examine the problem of the quantum resources that are necessary for quantum error correction protocols to succeed while simultaneously allowing for quantum enhanced metrology. Interestingly, we find that there exist regimes where this can occur without the presence of quantum entanglement, thus requiring us to invoke more general notions of non-classicality such as quantum discord in order to account for the success such protocols. This joins a list of known applications for quantum discord in quantum information. Quantum discord was also considered previously in various other specialized metrological scenarios.
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