Projective measurements are a powerful tool for manipulating quantum states. In particular, a set of qubits can be entangled by measuring a joint property such as qubit parity. These joint measurements do not require a direct interaction between qubits and therefore provide a unique resource for quantum information processing with well-isolated qubits. Numerous schemes for entanglement-by-measurement of solid-state qubits have been proposed, but the demanding experimental requirements have so far hindered implementations. Here we realize a two-qubit parity measurement on nuclear spins localized near a nitrogen-vacancy centre in diamond by exploiting an electron spin as a readout ancilla. The measurement enables us to project the initially uncorrelated nuclear spins into maximally entangled states. By combining this entanglement with single-shot readout we demonstrate the first violation of Bell's inequality with solid-state spins. These results introduce a new class of experiments in which projective measurements create, protect and manipulate entanglement between solid-state qubits. © 2013 Macmillan Publishers Limited.
CITATION STYLE
Pfaff, W., Taminiau, T. H., Robledo, L., Bernien, H., Markham, M., Twitchen, D. J., & Hanson, R. (2013). Demonstration of entanglement-by-measurement of solid-state qubits. Nature Physics, 9(1), 29–33. https://doi.org/10.1038/nphys2444
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