Detecting the origins of quantum heat in a circuit QED system*

The field of thermodynamics was born with the intent to convert the kinetic energy of the random velocity of thermalized particles, i.e. heat, into useful work. Using a similar analogy, a central goal of quantum thermodynamics consists in harnessing the randomness of the quantum measurement backaction and converting it into work. A two level system (TLS) with energy separation E brought into superposition, once measured, will randomly collapse into one of its two energy eigenstates, thus resulting in a final state whose energy can vary by E. Energy conservation principles dictate that this energy Ε, gained or lost by the TLS post measurement, must be exchanged with the environment. Due to the spontaneous nature of this energy exchange enabled by the measurement backaction, it is dubbed quantum heat. Here, using a circuit QED transmon system in the dispersive limit, we aim to measure and quantify the origins of quantum heat. Our results pave the way for further quantum thermodynamics experiments, such as a quantum Maxwell's demon functioning as a true quantum heat engine.