New J. Phys. 12 083034 (2010)
Phys. Rev. Lett. 105, 200501 (2010)
Nat. Commun. 2 , 184 (2011)
The results of local measurements on some composite quantum systems cannot be reproduced classically. This impossibility, known as quantum nonlocality, represents a milestone in the foundations of quantum theory. Quantum nonlocality is also a valuable resource for information-processing tasks, for example, quantum communication, quantum key distribution, quantum state estimation or randomness extraction. Still, deciding whether a quantum state is nonlocal remains a challenging problem.
Phys. Rev. Lett. 105, 160501 (2010)
We propose a hybrid (continuous-discrete variable) quantum repeater protocol for long-distance entanglement distribution. Starting from states created by single-photon detection, we show how entangled coherent state superpositions can be generated by means of homodyne detection. We show that near-deterministic entanglement swapping with such states is possible using only linear optics and homodyne detectors, and we evaluate the performance of our protocol combining these elements.
Appl. Phys. Lett. 97, 031104 (2010)
Phys. Rev. Lett. 105, 060504 (2010)
Phys. Rev. Lett. 105, 010502 (2010)
Phys. Rev. Lett. 106, 020402 (2011)
We investigate nonlocality distillation using measures of nonlocality based on the Elitzur-Popescu-Rohrlich decomposition. For a certain number of copies of a given nonlocal box, we define two quantities of interest: (i) the nonlocal cost and (ii) the distillable nonlocality. We find that there exist boxes whose distillable nonlocality is strictly smaller than their nonlocal cost. Thus nonlocality displays a form of irreversibility which we term “bound nonlocality.” Finally, we show that nonlocal distillability can be activated.
Mikael Afzelius and Christoph Simon
Phys. Rev. A 82, 022310 (2010)
Phys. Rev. A 82, 032317 (2010)