# Operations on spin qubits (beginner level)

Classical computers work using chips that consist of millions of transistors. You may already know that the concept of spin qubits is based on these transistors, which makes it easy to envision a similar picture of millions of quantum bits on a single chip.

But okay, suppose we can put many spin qubits on a single chip, what could we do with it? Team leader and roadmap leader at QuTech Menno Veldhorst will tell you all about the basic operations on such qubits in this video. Specifically on how they can be initialized and read-out, and how we can control such qubits (meaning how we can manipulate their states). As well as how the coupling between two qubits allows us to execute two-qubit logic gates, which is an essential building block for a multitude of quantum applications.

## Prerequisite knowledge

- Spin qubits
- Zeeman energy
- Qubit decoherence
- Bloch sphere

## Further Thinking

We have seen that in order to have a qubit in a quantum dot 2 magnetic fields are needed. One of these is perpendicular to the plane (applied magnetic field), whereas the other one is on it (alternating magnetic field). Can you tell why each of them is needed?

## Further reading

Take a look at this review paper discussing the field of spins in quantum dots.

- https://qutech.nl/wp-content/uploads/2020/03/2019_08_PhysicsToday_pt.3.4270.pdf (L. M. K. Vandersypen and M. A. Eriksson, Physics Today 72, 8, 38, 2019)
- https://arxiv.org/pdf/1204.5917.pdf (C. Kloeffel and D. Loss, 2012)

For more recent research, you might want to check out these papers:

- https://arxiv.org/abs/1904.11443 (Hendrickx et al., 2019)
- https://arxiv.org/abs/1910.05289 (Petit et al., 2019)

In the paper by Watson et al. (2018), they show the experimental realisation of two quantum algorithms with a two spin qubits quantum processor.

- https://arxiv.org/abs/1708.04214 (Watson et al., 2018)