Periodically driving a many-body localized quantum system

We experimentally study a periodically driven many-body localized system realized by interacting fermions in a one-dimensional quasi-disordered optical lattice. By preparing the system in a far-from-equilibrium state and monitoring the remains of an imprinted density pattern, we identify a localized phase at high drive frequencies and an ergodic phase at low ones. These two distinct phases are separated by a dynamical phase transition which depends on both the drive frequency and the drive strength. Our observations are quantitatively supported by numerical simulations and are directly connected to the change in the statistical properties of the effective Floquet Hamiltonian.We acknowledge support from Technical University of Munich - Institute for Advanced Study, funded by the German Excellence Initiative and the European Union FP7 under grant agreement 291763, from the DFG grant no. KN 1254/1-1, the European Commission (UQUAM, AQuS) and the Nanosystems Initiative Munich (NIM)

On Trial : the Compatibility of Measurement in the Physical and Social Sciences

In this paper, we put social measurement on trial: providing two perspectives arguing why measurement in the social and in the physical sciences are incompatible and counter with two perspectives supporting compatibility. For the case 'against', we first argue that there is a lack of definition in the social sciences. Thus, while measurement in the physical sciences is supported by empirical evidence, calibrated instruments, and predictive theory that work together to test the quantitative nature of properties, measurement in the social sciences, in the main, rests on a vague, discretionary definition of measurement that places hardly any restrictions on empirical data, does not require calibrated instruments, and rarely articulates predictive theories. The second argument for the case 'against' introduces the problem associated with psychometrics, including different approaches, methodologies, criteria for success and failure, and considerations as to what counts as measurement. Making the first case 'for', we highlight practical principles for improved social measurement including units, laws, theory, and metrology. The second argument 'for' introduces the exemplar of the Lexile Framework for reading that exploits metrological principles and parallels the paths taken by, for example, thermometry. We conclude by proposing a way forward potentially applicable to both physical and social measurement, in which inferences are modelled in terms of a measurement system, where specifically the output of the instrument in response to probing the object ('entity') is a performance metric, i.e. how well the set-up performs the assessment