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Quantum Computer

01 /Quantum Computers 02 /How to build a qubit 03 /Spin qubits (beginner level) 04 /Operations on spin qubits (beginner level) 05 /Electron spin qubits 06 /Capturing a single electron 07 /Quantum dot qubits 08 /Quantum control and readout 09 /Qubit errors 10 /NV center qubits 11 /Operations on NV center qubits 12 /The Transmon Qubit - A basis for the Quantum Computer 13 /Operations on the Transmon Qubit - Circuit QED 14 /Single-qubit operations on the Transmon qubit 15 /Measurements on the Transmon Qubit 16 /Two-qubit operations on the Transmon qubit 17 /Topological qubits: Anyons 18 /Operations on anyons: Braiding 19 /Operations on anyons: Real-life experiments 20 /Topological quantum computing: Majorana fermions and where to find them 21 /Majorana bound states in superconductors 22 /How do you measure Majorana bound states? 23 /A framework for the future Quantum Computer 24 /The Building Blocks of a Quantum Computer 25 /How to build a Quantum Algorithm - Quantum Circuits 26 /How do you program a quantum algorithm? 27 /The compiler of a quantum computer 28 /Micro-architectures 29 /How do we connect our quantum system to a classical interface? 30 /Assembling a Quantum Processor 31 /Microwave drivers for qubits 32 /Implementation of microwave drivers 33 /Quantum error correction 34 /Surface codes 35 /Fault-tolerant Quantum Error Correction with surface codes

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?

Solution

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. 

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)!