3.2.1 Measuring two qubits

Measurement for two-qubit states is defined in a very similar way to Eq. 2.7 for one-qubit states, except as an outcome you get two bits with the following probabilities:

(3.51)

Here we use light green for quantum bits and gray for the resulting two deterministic bits after the measurement. How can we measure both qubits in Quirky? We simply add two measurements, one for each qubit, and use the probability display just like before: