Resonance Transport and Kinetic Entropy

Within the real-time formulation of nonequilibrium field theory, generalized transport equations are derived avoiding the standard quasiparticle approximation. They permit to include unstable particles into the transport scheme. In order to achieve a self-consistent, conserving and thermodynamically consistent description, we generalize the Baym's $\Phi$-functional method to genuine nonequilibrium processes. The developed transport description naturally includes all those quantum features already inherent in the corresponding equilibrium limit. Memory effects appearing in collision term diagrams of higher order are discussed. The variational properties of $\Phi$-functional permit to derive a generalized expression for the non-equilibrium kinetic entropy flow, which includes fluctuations and mass width effects. In special cases an $H$-theorem is demonstrated implying that the entropy can only increase with time. Memory effects in the kinetic terms provide corrections to the kinetic entropy flow that in equilibrium limit recover the famous bosonic type $T^3 \ln T$ correction to the specific heat of Fermi liquids like Helium-3.Comment: 50 pages, submitted to Nucl. Phys.

Pulsed quantum optomechanics

Studying mechanical resonators via radiation pressure offers a rich avenue for the exploration of quantum mechanical behavior in a macroscopic regime. However, quantum state preparation and especially quantum state reconstruction of mechanical oscillators remains a significant challenge. Here we propose a scheme to realize quantum state tomography, squeezing and state purification of a mechanical resonator using short optical pulses. The scheme presented allows observation of mechanical quantum features despite preparation from a thermal state and is shown to be experimentally feasible using optical microcavities. Our framework thus provides a promising means to explore the quantum nature of massive mechanical oscillators and can be applied to other systems such as trapped ions.Comment: 9 pages, 4 figure

Revealing correlations between a system and an inaccessible environment

How can we detect that our local, controllable quantum system is correlated with some other inaccessible environmental system? The local detection method developed in recent years allows to realize a dynamical witness for correlations without requiring knowledge of or access to the environment that is correlated with the local accessible quantum system. Here, we provide a brief summary of the theoretical method and recent experimental studies with single photons and trapped ions coupled to increasingly complex environments.Comment: 12 pages, 3 figure

Near-Optimal Adversarial Policy Switching for Decentralized Asynchronous Multi-Agent Systems

A key challenge in multi-robot and multi-agent systems is generating solutions that are robust to other self-interested or even adversarial parties who actively try to prevent the agents from achieving their goals. The practicality of existing works addressing this challenge is limited to only small-scale synchronous decision-making scenarios or a single agent planning its best response against a single adversary with fixed, procedurally characterized strategies. In contrast this paper considers a more realistic class of problems where a team of asynchronous agents with limited observation and communication capabilities need to compete against multiple strategic adversaries with changing strategies. This problem necessitates agents that can coordinate to detect changes in adversary strategies and plan the best response accordingly. Our approach first optimizes a set of stratagems that represent these best responses. These optimized stratagems are then integrated into a unified policy that can detect and respond when the adversaries change their strategies. The near-optimality of the proposed framework is established theoretically as well as demonstrated empirically in simulation and hardware

Information-flux approach to multiple-spin dynamics

We introduce and formalize the concept of information flux in a many-body register as the influence that the dynamics of a specific element receive from any other element of the register. By quantifying the information flux in a protocol, we can design the most appropriate initial state of the system and, noticeably, the distribution of coupling strengths among the parts of the register itself. The intuitive nature of this tool and its flexibility, which allow for easily manageable numerical approaches when analytic expressions are not straightforward, are greatly useful in interacting many-body systems such as quantum spin chains. We illustrate the use of this concept in quantum cloning and quantum state transfer and we also sketch its extension to non-unitary dynamics.Comment: 7 pages, 4 figures, RevTeX

Communicative Competencies and the Structuration of Expectations: The creative tension between Habermas' critical theory and Luhmann's social systems theory

I elaborate on the tension between Luhmann's social systems theory and Habermas' theory of communicative action, and argue that this tension can be resolved by focusing on language as the interhuman medium of the communication which enables us to develop symbolically generalized media of communication such as truth, love, power, etc. Following Luhmann, the layers of self-organization among the differently codified subsystems of communication versus organization of meaning at contingent interfaces can analytically be distinguished as compatible, yet empirically researchable alternatives to Habermas' distinction between "system" and "lifeworld." Mediation by a facilitator can then be considered as a special case of organizing historically contingent translations among the evolutionarily developing fluxes of intentions and expectations. Accordingly, I suggest modifying Giddens' terminology into "a theory of the structuration of expectations.