Investigation of Landauer's principle in a qubit erasure protocol at finite temperature.*

More than sixty years ago, Landauer’s principle demonstrated a fundamental link between information theory and classical thermodynamics. The principle states that any irreversible informational process that occurs in a system is inevitably accompanied by the dissipation of heat into the environment. The principle was experimentally verified in the last decade with many different systems, including a trapped colloidal particle, a single atom, and a micromechanical oscillator. However, an absolute quantum version of the idea is still under debate and has attracted researchers from many different areas. Specifically, we have witnessed a renewed interest in this topic since the recent emergence of the area of quantum thermodynamics. In the present work, we propose a quantum information erasure protocol and analyze its implications in light of Landauer’s principle. The protocol relies on the use of the degeneracy in the degrees of freedom of a structured qubit-like reservoir to erase a given information stored in a qubit memory.  In this perspective, we can explicitly calculate

the change in the von Neumann entropy of the system, along with the heat dissipated to the degrees of freedom of the environment. Also, we provide an experimental testbed for the protocol based on an all-optical circuit with only linear optical devices. In this case, the polarization degree of freedom encodes the information to be erased in the memory, and the path degree of freedom plays the role of the reservoir. Likewise, a quantum circuit model is provided so that the steps of the erasure can be reproduced in other quantum platforms. As such, the model provides a simple and practical architecture for the realization of tests of the Landauer principle in a quantum-mechanical scenario.