Thermodynamics of ancilla-assisted erasure of quantum information

Landauer’s principle sets a fundamental limit on the heat dissipated when one classical bit of information is erased from a memory, thereby establishing a direct link between information theory and thermodynamics. With the advent of quantum technologies, a natural question arises: How does Landauer’s principle extend to the quantum regime? In this work, we study the thermodynamics of a quantum channel that erases an arbitrary state of a qubit memory in contact with a reservoir composed of a thermal qubit and a pure ancilla qubit. The channel is based only on CNOT gates, and the introduction of the ancilla makes it capable of operating beyond Landauer’s limit, when the temperature of the thermal qubit is above a given limit temperature. However, we observe that, since the introduction of the ancilla does not correspond to a strict Landauer’s scenario, our protocol does not represent a violation of Landauer’s principle.