Abstract:
Large-scale quantum networks are a promising architecture for quantum communication and distributed quantum computing. Such a network requires controlled nodes and a method to link them together by distributing entanglement over large distances. The nitrogen-vacancy center (NV) in diamond provides a rare combination: the NV electronic spin couples to nearby nuclear spins so that a controlled few-quantum-bit register can be formed, and, at the same time, the NV’s strong optical transition provides the potential to link distant NV centers through photons.
Here I will discuss two key experimental advances towards quantum networks based on spins in diamond, recently made in our group [1, 2]. First, I will present the entanglement of two NV centers separated by a distance of 3 meters [1]. Second, we entangled two individual nuclear spins near an NV center and realized a violation of a Bell inequality without assuming fair-sampling, demonstrating high-quality initialization, control and single-shot readout of multiple nuclear spins [2]. Together with recent advances that extend the number of nuclear spins that can be controlled [3, 4] these two experiments provide a compelling pathway towards quantum networks of spins in diamond.
[1] W. Pfaff et al., Nature Phys. 9, 29 (2013)
[2] H. Bernien et al., Nature, 497, 86 (2013)
[3] T. van der Sar et al., Nature 484, 82 (2012)