In my article titled Reverse Engineering Quantum Black Boxes, I peeked inside the black box featured in this Turn the Qubits Off puzzle. And while my version of the black box accurately created the puzzle’s quantum states, it did so in a very different manner than the black box in the actual puzzle. I have thus far identified two reasons how this happened.
Quirk vs IBM Q
The setting for the puzzle is a stripped down version of the Quirk online quantum computing simulator. If you play around with the drag-and-drop circuit builder, you’ll see that you can create a wide variety of multi-qubit operations.
the minimalist solution, image used with permission from Quantum Intuition (@explore_quantum)
However, I am not a regular user of Quirk; I am a regular user of IBM Q. Therefore, I restricted myself to gate operations I would use if building the circuit using OpenQASM (Quantum Assembly Language). This is evident, perhaps, by the fact that I actually ran my circuit on ibmqx2.
