Teaching decoherence by simulating single-spin quantum channels on IBM's quantum computer

Decoherence is often not discussed in undergraduate quantum-mechanics classes. The simplest case to consider is the decoherence of a single spin. We believe that formal work on quantum channels benefits from practical work, where the quantum channel is simulated on quantum hardware, allowing for single-quantum experiments without complicated lab equipment. Using the IBM quantum experience on the cloud, we examine depolarizing, amplitude damping, dephasing, and thermalizing channels. These channels are first described in terms of Kraus operators and then they are converted to quantum circuits that involve mid-circuit resets. More complex circuits for Ramsey oscillations and spin-echo experiments are also examined. This hands-on approach to decoherence should help students learn an important branch of quantum information science.