# NV center qubits

As you might know, there are several ways to make actual qubits in quantum computers. One of those ways is by using an electron spin inside a Nitrogen-Vacancy (NV) center in a diamond lattice. These qubits have a long coherence time and can work at a large variety of temperatures (including room temperature!). You will see that that and most of the other key features of NV center qubits are quite handy in (for example) quantum network applications.

This video, presented by QuTech group leader Tim Taminiau, we will look at the basics for such a qubit. We will discuss some applications and see how the sample physically looks like, as well as briefly explain the basic ways how we can control and readout the electron spin in such an NV center.

## Prerequisite knowledge

- Coherence times
- Basic physics (what are photons, wavelength of photons, spin-1 system)
- Entanglement

## Further Thinking

In the video, Tim explains that NV centers are promising candidates as nodes in a quantum network, if only because of the relatively straightforward (optical) way we can connect the electron spins between two nodes. Tim also explains the nuclear spins around such an NV center. What do you think can be the primary purpose for those nuclear spins in such a quantum network?

## Further reading

There are many papers to read about NV centers in diamond. Most of the papers are quite technical, but very interesting to read nonetheless. Give it a go!

This review article by F. Jelezko & J. Wrachtrup gives an expert introduction for defects in diamond (of which the NV is one version).

Here a research group from Delft demonstrates an entangled link between two NV nodes that are roughly 1.3 km apart.

- https://arxiv.org/abs/1603.05705 (Hensen et al., 2015)

The group of Tim Taminiau (the lecturer in this video) is doing much research on using nuclear spins around such an NV center. Two recent publications are

- https://arxiv.org/abs/1905.02094 (Bradley et al., 2019)

Here they use 10 nuclear spins to build a quantum register and perform an actual quantum algorithm. - https://arxiv.org/abs/1905.02095 (Abobeih et al., 2019)

Here the group demonstrates another application for NV centers in diamond: quantum sensing. By using a complex sequence, they can locate the position (x,y,z-coordinate, that is) of 27 nuclear spins around the NV center with sub-angstrom precision (less than 0.1 nm)!