Faculty @ Washington U. in St. Louis, US
Tuesday June 28 – 18.30 BST
Energetic cost of measurements using quantum, coherent, and thermal light
In the quantum information literature, the basic concepts are unitary operators, quantum gates, entangling operations, and measurements. These are all applied to accomplish tasks in quantum information processing. However, much like classical computers, all logical operations demand resources. In particular, dissipative operations, such as measurement and erasure, are nonconservative operations, and must also generate entropy – and are therefore connected to and constrained by the laws of thermodynamics. I will present our recent experimental work investigating quantum measurement from the perspective of thermodynamical and quantum resources. Using a superconducting qubit and the physics of cavity quantum electrodynamics, we have characterized measurement efficiency and effectiveness for different thermal, coherent, and quantum states of light. In particular, we find that thermal light is capable of performing quantum measurements with comparable efficiency to coherent light, both being outperformed by single-photon light. These experiments elucidate the physics of quantum measurement, deepening our understanding of the thermodynamics of quantum information.