Algorithm 2: Deutsch and Jozsa [10]

Proceed with the following steps. Prepare an n-qubit query register in the state $\left|0\right.〉$, and an output qubit in $\left|1\right.〉$. Apply the Walsh-Hadamard transform to the query register and the output qubit. Apply the oracle. Apply the Walsh-Hadamard transform to the query register. Test if the output state of the query register is $\left|0\right.〉$ by a measurement of the observable $\left|0\rangle \langle 0\right|\otimes I_2$.   If the test is positive, output “constant,” otherwise “balanced”.