J. J. Alonso

Non-equilibrium thermodynamics of continuously measured quantum systems: a circuit-QED implementation

  1. P. G. Di Stefano,
  2. J. J. Alonso,
  3. E. Lutz,
  4. G. Falci,
  5. and M. Paternostro
We propose a fully operational framework to study the non-equilibrium thermodynamics of a quantum system S that is coupled to a detector D whose state is continuously monitored, allowing
to single out individual quantum trajectories of S. We focus on detailed fluctuation theorems and characterize the entropy production of the system. We establish fundamental differences with respect to the thermodynamic of unmonitored, unitarily evolved systems. We consider the paradigmatic example of circuit-QED, where superconducting qubits can be coupled to a continuously monitored resonator and show numerical simulations using state of the art experimental parameters.
arxiv pdf

Thermodynamics along individual trajectories of a quantum bit

  1. M. Naghiloo,
  2. D. Tan,
  3. P. M. Harrington,
  4. J. J. Alonso,
  5. E. Lutz,
  6. A. Romito,
  7. and K. W. Murch
We use a near-quantum-limited detector to experimentally track individual quantum trajectories of a driven qubit formed by the hybridization of a waveguide cavity and a transmon circuit.
For each measured quantum coherent trajectory, we separately identify energy changes of the qubit as heat and work, and verify the first law of thermodynamics for an open quantum system. We further employ a novel quantum feedback loop to compensate for the exchanged heat and effectively isolate the qubit. By verifying the Jarzynski equality for the distribution of applied work, we demonstrate the validity of the second law of thermodynamics. Our results establish thermodynamics along individual quantum trajectories.
arxiv pdf