Experimental Validation of Enhanced Information Capacity by Quantum Switch in Accordance with Thermodynamic Laws

TL;DR

This paper experimentally demonstrates that a quantum switch can increase information capacity in thermal channels without violating thermodynamic laws, highlighting its potential as a resource in quantum thermodynamics.

Contribution

It provides the first experimental validation of the quantum switch's capacity enhancement in thermal channels within thermodynamic constraints.

Findings

Quantum switch increases information capacity in thermal channels.

The capacity increase is consistent with thermodynamic laws.

The switch can generate non-thermal states from thermal states, consuming free energy.

Abstract

We experimentally probe the interplay of the quantum switch with the laws of thermodynamics. The quantum switch places two channels in a superposition of orders and may be applied to thermalizing channels. Quantum-switching thermal channels has been shown to give apparent violations of the second law. Central to these apparent violations is how quantum switching channels can increase the capacity to communicate information. We experimentally show this increase and how it is consistent with the laws of thermodynamics, demonstrating how thermodynamic resources are consumed. We use a nuclear magnetic resonance approach with coherently controlled interactions of nuclear spin qubits. We verify an analytical upper bound on the increase in capacity for channels that preserve energy and thermal states, and demonstrate that the bound can be exceeded for an energy-altering channel. We show that the switch can be used to take a thermal state to a state that is not thermal, whilst consuming free energy associated with the coherence of a control system. The results show how the switch can be incorporated into quantum thermodynamics experiments as an additional resource.