04.90.+t Entanglement transfer

High fidelity spin entanglement using optimal control


F. Dolde, V. Bergholm, Y. Wang, I. Jakobi, S. Pezzagna, J. Meijer, P. Neumann, T. Schulte-Herbrueggen, J. Biamonte, and J. Wrachtrup


Nature Communications 5, 3371 (2014)

Precise control of quantum systems is of fundamental importance in quantum information processing, quantum metrology and high-resolution spectroscopy. When scaling up quantum registers, several challenges arise: individual addressing of qubits while suppressing cross-talk, entangling distant nodes and decoupling unwanted interactions. Here we experimentally demonstrate optimal control of a prototype spin qubit system consisting of two proximal nitrogen-vacancy centres in diamond. Using engineered microwave pulses, we demonstrate single electron spin operations with a fidelity F≈0.99.

Matrix product states with long-range localizable entanglement


T. B. Wahl, D. Pérez-García, and J. I. Cirac


URL: http://link.aps.org/doi/10.1103/PhysRevA.86.062314
DOI: 10.1103/PhysRevA.86.062314
PACS: 03.67.Mn, 03.65.Ud, 75.10.Pq, 71.10.Hf

We derive a criterion to determine when a translationally invariant matrix product state (MPS) has long-range localizable entanglement, where that quantity remains finite in the thermodynamic limit. We give examples fulfilling this criterion and eventually use it to obtain all such MPS with bond dimension 2 and 3.

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