I present experiments on superconducting nano-circuits, which test the role of information in thermodynamics. Two types of Maxwell's demons (MD), a Szilard’s Engine and an autonomous MD, were realized based on single electrons. Ideally they extract heat and do work equal to kT log(2) per operation cycle, in accordance with the Landauer principle for the cost of erasing a single bit in computation. In our experiments we achieve 75% of this bound per cycle, and the missing efficiency can be quantitatively accounted for by assigning the entropy of mutual information, due to incomplete measurement, on the same footing as other contributions of entropy. In the second part of the talk I present quantum heat engine (refrigerator) based on a superconducting qubit.
We experimentally and theoretically investigate the non-linear dynamics of evanescently coupled nanolasers and its impact in terms of bifurcations and photon statistics. The nanolasers are fabricated in suspended 2D Photonic Crystal membranes, and studied as a function of pump power and coupling strength. The modification of coupling strength is obtained by an original engineering procedure that allows us to tune the coupling strength between the nanocavities without affecting the nanolaser performance . I will focus on two experiments. In the first one, the cavities are pumped in a quasi-stationnary regime. For certain conditions, we are able to observe a paradigmatic classical bifurcation: the spontaneous mirror-symmetry breaking . This is the first experimental demonstration of such transition in micro/nanophotonics. A pitchfork bifurcation reveals two localized states in the cavities. The symmetry breaking bifurcation has been observed with only ~150 intracavity photons, which makes this system promising to investigate non-classical photon correlations and nonlinear dynamical phenomena with few photons. In a second experiment, the nanolasers are pumped in a non-stationnary regime using short pulses  in order to investigate a new route for the generation and control of long tailed superthermal light. We analyze the heavy-tailed photon distributions (super-exponential) whose fluctuations are greater than those of thermal states and link, using a mean field model, both the emergence of the heavy tails and the superthermal nature of the nonlasing (symmetric, in-phase) mode. We show that passing through the lasing threshold corresponds to an abrupt decrease of the contribution of spontaneous emission —that plays the role of an effective temperature— during which the statistics of the nanolaser trajectories in phase space are dominated by nonlinear transport. Changing the duration of this out-of-equilibrium quenching phase, one obtains long-tailed distributions for the unstable in-phase mode in agreement with the experimental results.
A quantum turnstile is a nanoelectronic device which can transfer electrons one by one between two superconducting electrodes by periodically modulating the gate voltage on a small metallic grain located between the two electrodes. The coherent coupling between the discrete electronic level on the grain and the BCS singularities in the quasiparticle density of states on the electrodes imposes a fundamental restriction on the device operation.
Many-body localized (MBL) quantum systems show a drastic disregard for the Eigenstate Thermalization Hypothesis (ETH), giving rise to a fundamentally new dynamical quantum many-body phase. The existence of such a phase in *one-dimension* has been supported by multitude of theoretical studies. Much less so can be said about how the quantum many-body state changes from the ETH respecting phase to the MBL phase and even less is known about its dynamics in dimensions higher than one. To confront such cases, I will describe our efforts in creating and probing MBL with ultra-cold atoms in quasi-periodic optical lattices in one and two dimensions. Near the MBL regime we observe drastically slowed down dynamics. This can be attributed to be arising due to relaxation of (rare) configurational Griffiths-type regions. Further, by studying the relaxation dynamics of a far-from-equilibrium state, we find evidence for MBL in quasi-periodic potentials in both one and two dimensions. If time permits, I would also talk about a periodically driven *Floquet MBL phase*, demonstrating how MBL can even exist without (at least some) conventional conservation laws. Our results demonstrate how controlled quantum simulators can explore fundamental questions about quantum statistical mechanics in genuinely novel regimes, quite often not accessible to traditional numerical simulations.