| Abstract: | Discordant states appear in a large number of quantum phenomena and seem to be a good indicator of divergence from classicality. While there is evidence that they are essential for a quantum algorithm to have an advantage over a classical one, their precise role is unclear. We examine the role of discord in quantum computation using the paradigmatic framework of restricted distributed quantum gates and show that manipulating discordant states using local operations has an associated cost in terms of entanglement and communication resources. Changing discord reduces the total correlations and operations on discordant states require entanglement resources. Discord is, however, only one measure in a hierarchy of similar quantities which we call K-discord, each restricting the kinds of operations that can be performed without entanglement resources. [1] Quantum discord, local operations, and Maxwell’s demons, A.Brodutch and D.R.Terno; Phys. Rev. A 81, 062103 (2010); arXiv:1002.4913 [2] Entanglement, discord, and the power of quantum computation, A.Brodutch and D.R.Terno; Phys. Rev. A 83, 010301(R) (2011); arXiv:1009.2571 [3] The classical-quantum boundary for correlations: discord and related measures K. Modi, A. Brodutch, H. Cable, T. Paterek, V. Vedral; Rev. Mod. Phys. (2012); arXiv:1112.6238 [4] Discord and quantum computational resources, A. Brodutch arXiv:1027.5105 (2012) |
