The thermodynamic cost of quantum measurements in the circuit quantum electrodynamics architecture*

Quantum measurements are basic operations in the study of quantum information. As with classical computers, all logical operations demand resources. Here we investigate the resources required to perform quantum measurements of a qubit. We utilize different quantum and classical states of light in a circuit quantum electrodynamics setup to perform measurements, characterizing both the measurement backaction and measurement efficiency. We find that in the strong dispersive limit the thermal light is capable of performing quantum measurements with comparable efficiency to coherent light. We also analyze the energetic and entropic costs of these quantum measurements at different measurement strengths. This work demonstrates a new efficient approach to quantum measurements in circuit quantum electrodynamics. Furthermore, we connect concepts in information thermodynamics to quantum measurement by comparing the information gain per photon for each input field.