Fun With IBM Quantum Reset Gates
Your first quantum computing circuit, the “hello, quantum world" circuit, looks very similar to the circuit above. You learn about superposition and apply a Hadamard gate, and then you learn about entanglement and apply a CNOT gate. This article does not rehash the plethora of tutorials out there.
Recently, IBM Quantum modified some of its devices to finally allow reset gates. Previously, you could only initialize qubits, apply operations to them, and then measure them. Now, you can initialize them, use them, reset them, and use them again.
Going back to where we left off in the circuit, the measurement results should show a roughly 50% probability of measuring |00> and a roughly 50% probability of measuring |11>. However, we’re going to reset that first qubit and apply a NOT gate so that the first qubit should always measure |1>.
As you can see, the first qubit does have a high probability of measuring |1>. And, as you can also see, the second qubit retains the roughly 50/50 probability of measuring either |0> or |1>, albeit a little skewed toward |0>.
Even more features are on the way whenever OpenQASM3 is launched, but this still opens up possibilities in the meantime.