Thermodynamical detection of entanglement by Maxwell's demons (5 pages)

Wojciech Hubert Zurek

Koji Maruyama, Fumiaki Morikoshi, Vlatko Vedral

Quantum correlation, or entanglement, is now believed to be an indispensable physical resource for certain tasks in quantum information processing, for which classically correlated states cannot be useful. Besides information processing, what kind of physical processes can exploit entanglement? In this paper, we show that there is indeed a more basic relationship between entanglement and its usefulness in thermodynamics. We derive an inequality showing that we can extract more work out of a heat bath via entangled systems than via classically correlated ones. We also analyze the work balance of the process as a heat engine, in connection with the second law of thermodynamics.

Omar Osenda, G. A. Raggio

Miłosz R. Michalski

Mario Arnolfo Ciampini, Luca Mancino, Adeline Orieux +4 more

We adopt the paradigm of Maxwell’s demon to witness entanglement in a two-qubit state. Our experiment goes towards understanding how entanglement effects the efficiency of quantum thermodynamic machines, a problem of foundational and practical relevance.

W.-B. Wang, X.-Y. Chang, F. Wang +9 more

We report experimental realization of a quantum version of Maxwell's demon using solid state spins where the information acquiring and feedback operations by the demon are achieved through conditional quantum gates. A unique feature of this implementation is that the demon can start in a quantum superposition state or in an entangled state with an ancilla observer. Through quantum state tomography, we measure the entropy in the system, demon, and the ancilla, showing the influence of coherence and entanglement on the result. A quantum implementation of Maxwell's demon adds more controllability to this paradoxical thermal machine and may find applications in quantum thermodynamics involving microscopic systems.