# Measurement operators

Now that we have learned about the Born Rule, we are able to study the measurements and how they affect a quantum state. Arjen Vaartjes (QuTech) helps us understand how a projective quantum measurement can be expressed in the braket notation. This is done by the measurement operators, which let us know the probability of measuring a certain state and the remaining state after performing such a measurement.

## Prerequisite knowledge

- Bra-ket notation
- Born rule
- Basic linear algebra

## Further thinking

What is the probability of obtaining the result |0> when measuring the following state?

## Further reading

For a more advanced view on measurement operators see section 1.8 and 1.9 in N. D. Mermin, â€˜Quantum Computer Science: An Introductionâ€™ and section 2.2.3 of M. A. Nielsen and I. L. Chuang, Quantum computation and quantum information, 10th anniversary ed. Cambridge ; New York: Cambridge University Press, 2010.