Unlocking of a correlation refers to the unexpected phenomenon that a small amount of communication increases that correlation (as a function of the state of the distributed system) by a disproportionate amount. Locki...
We present a communication protocol for the erasure channel assisted by backward classical communication, which achieves a significantly better rate than the best prior result. In addition, we prove an upper bound for...
We present a communication protocol for the erasure channel assisted by backward classical communication, which achieves a significantly better rate than the best prior result. In addition, we prove an upper bound for the capacity of the channel. The upper bound is smaller than the capacity of the erasure channel when it is assisted by two-way classical communication. Thus, we prove the separation between quantum capacities assisted by backward classical communication and two-way classical communication.
This is a comment on the article "A quantum Algorithm for the Hamiltonian NAND Tree" by Edward Farhi, Jeffrey Goldstone, and Sam Gutmann, Theory of computing 4 (2008) 169–190. That paper gave a quantum algo...
We apply the Lieb-Robinson bounds technique to find the maximum speed of interaction in a spin model with topological order whose low-energy effective theory describes light [see X.-G. Wen, Phys. Rev. B 68, 115413 (20...
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We apply the Lieb-Robinson bounds technique to find the maximum speed of interaction in a spin model with topological order whose low-energy effective theory describes light [see X.-G. Wen, Phys. Rev. B 68, 115413 (2003)]. The maximum speed of interactions in two dimensions is bounded from above by less than e times the speed of emerging light, giving a strong indication that light is indeed the maximum speed of interactions. This result does not rely on mean field theoretic methods. In higher spatial dimensions, the Lieb-Robinson speed is conjectured to increase linearly with the dimension itself. The implications for the horizon problem in cosmology are discussed.
The only information available about an alleged source of entangled quantum states is the amount S by which the Clauser-Horne-Shimony-Holt inequality is violated: nothing is known about the nature of the system or the...
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The only information available about an alleged source of entangled quantum states is the amount S by which the Clauser-Horne-Shimony-Holt inequality is violated: nothing is known about the nature of the system or the measurements that are performed. We discuss how the quality of the source can be assessed in this black-box scenario, as compared to an ideal source that would produce maximally entangled states (more precisely, any state for which S=22). To this end, we present several inequivalent notions of fidelity, each one related to the use one can make of the source after having assessed it, and we derive quantitative bounds for each of them in terms of the violation S. We also derive a lower bound on the entanglement of the source as a function of S only.
Cubelike graphs are the Cayley graphs of the elementary Abelian group Z2n (e.g., the hypercube is a cubelike graph). We study perfect state transfer between two particles in quantum networks modeled by a large class o...
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Cubelike graphs are the Cayley graphs of the elementary Abelian group Z2n (e.g., the hypercube is a cubelike graph). We study perfect state transfer between two particles in quantum networks modeled by a large class of cubelike graphs. This generalizes the results of Christandl et al. [Phys. Rev. Lett. 92, 187902 (2004)] and Facer et al. [Phys. Rev. A 92, 187902 (2008)].
We consider asymptotic capacities of bipartite unitary gates. We present a gate with exponen- tially larger entanglement capacity than the total communication capacity. The key tool is a communication- efficient metho...
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We consider asymptotic capacities of bipartite unitary gates. We present a gate with exponentially larger entanglement capacity than the total communication capacity. The key tool in our proof, which may be of indepen...
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We consider asymptotic capacities of bipartite unitary gates. We present a gate with exponentially larger entanglement capacity than the total communication capacity. The key tool in our proof, which may be of independent interest, is a communication-efficient protocol for testing whether a bipartite quantum state belongs to a short list of candidate states.
We study the problem of the practical realization of an abstract quantum circuit when executed on a quantum hardware. By practical, we mean adapting the circuit to particulars of the physical environment which restric...
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