22ème conférence Claude Itzykson - Manipulation of Simple Quantum Systems

Titles and abstracts

3. Tomaz Prosen: Diffusive transport in Integrable lattice systems

06/06/2017 10:15

Integrable systems, having an extensive number of conserved quantities, are typically associated with ballistic transport. This picture is theoretically justified in terms of Mazur bounds [1], or the emerging field of generalized hydrodynamics [2]. However, for systems posessing parity-type symmetries (such as spin-reversal or parity-hole) there exist generic symmetric states for which...

4. Pierre Rouchon: Towards generic adiabatic elimination for bipartite open quantum systems

06/06/2017 11:45

This joint work with R. Azouit, F. Chittaro and A. Sarlette consider a composite quantum system consisting of a fast dissipative subsystem coupled to a slow one. Using the time-scale separation, we develop an adiabatic elimination technique to derive at any order the reduced model describing the slow subsystem. The method, based on an asymptotic expansion and geometric singular perturbation...

5. Clément Pellegrini: Invariant measure for quantum trajectories

06/06/2017 14:00

Quantum trajectories describe the evolution of a quantum system monitored by indirect measurement. The evolution is random and is usually described by Markov processes, either solution of stochastic differential equations or Markov chains. It is then natural to study the large time behaviour of such evolution, this is related to the notion of invariant measure. In this talk we present...

6. Benjamin Huard: Quantum trajectories and feedback based on the measurement of decoherence channels in a qubit

06/06/2017 15:00

Decoherence can be understood as the result of unread measurements of the system by its environment. For a superconducting qubit, the two main corresponding jump operators are the lowering operator and the Hamiltonian operator. While the former is associated with the detection of an emitted photon by fluorescence, the latter can be associated with the detection of a frequency shift of a...

7. Iosif Bena: Black Holes, where Quantum Mechanics and General Relativity clash

06/06/2017 16:30

Einstein’s General Relativity applied to black holes appears to lead to Information loss, thus violating one of the fundamental tenets of Quantum Mechanics. Recent Quantum Information Theory based arguments imply that information loss can only be avoided if at the scale of the black hole horizon there exists a structure (commonly called fuzzball or firewall) that allows information to escape....

17. Michel Brune: Quantum trajectory of a field stored in a cavity, the past quantum state approach

07/06/2017 09:30

We perform experiments where photons are trapped in a nearly ideal “photon box” as discussed by Einstein and Bohr in one of the gedanken experiments they introduced for emphasizing the unbelievable strangeness of quantum theory. Our photon box consists in a high Q cavity trapping microwave photons between superconducting mirrors. In the experiments, we probe and manipulate the trapped...

9. Guillaume Aubrun: Convex geometry and high-dimensional entanglement

07/06/2017 10:30

We will consider the phenomenon of quantum entanglement from the point of view of high-dimensional convex geometry. We estimate several geometric invariants (volume, mean width, approximability by polytopes) associated with the convex set consisting of all unentangled quantum states, and with the dual set. This information can be translated into results about the complexity of entanglement, or...

10. Mazyar Mirrahimi: Dissipation as a resource for stabilizing quantum states with superconducting qubits

07/06/2017 12:00

Recent advances in quantum-limited amplification have opened doors to high-fidelity non-demolition measurement of superconducting qubits and have already led to successful experiments on closed-loop control of such systems. However, the finite bandwidth of the amplification procedure, together with the time-consuming data acquisition and post-treatment of the output signal, lead to important...

11. Julia Kempe: Battling Decoherence, from quantum error correction to the three-electron qubit

07/06/2017 14:15

In this talk we give a brief survey on ways to encode quantum information in order to protect it against decoherence and noise. We will give a quick overview of quantum error correction with it's challenges and applicability, and then describe an alternative way to avoid decoherence: decoherence-free subspaces. We will focus on the 3-qubit exchange qubit and also give a surprising connection...

12. Antoine Tilloy: Non-Markovian linear quantum feedback of continuous measurements

07/06/2017 15:15

Continuous measurement schemes have an interest beyond the simple unraveling of an open system evolution as they allow for control. Indeed, a certain function of the past measurement signal can be fed back into the system through an external drive to provide e.g. a controllable dissipation source, stabilize a state or purify it faster. However, very few situations yield a manageable master...

13. Yves Couder: Wave-particle duality as it emerges in the dynamics of a classical particle driven by its memory-endowed wave-field

07/06/2017 16:45

We have introduced, some time ago, an experimental system in which a droplet bouncing on a vertically vibrated liquid interface can become self-propelled by its interaction with the waves it generates. It thus becomes a self-propelled "walker", a symbiotic object formed by the droplet and its associated wave. ­­A specificity of this system is that owing to the parametric forcing due to the...

14. Patrice Bertet: Magnetic resonance at the quantum limit and beyond

08/06/2017 09:30

The detection and characterization of paramagnetic species by electron-spin resonance (ESR) spectroscopy has numerous applications in chemistry, biology, and materials science [1]. Most ESR spectrometers rely on the inductive detection of the small microwave signals emitted by the spins during their Larmor precession into a microwave resonator in which they are embedded. Using the tools...

15. Jürg Fröhlich: Dynamics of Quantum Systems Featuring Events

08/06/2017 10:30

I report on results concerning the stochastic dynamics of quantum systems featuring events and of systems under repeated observation. In particular, I will mention a new type of "quantum branching process" (apparently not studied by mathematicians, yet) and outline a theory of indirect measurements and of associated quantum jump processes.

16. Christoph Westbrook: Using phonons to simulate the behavior of other quantum fields

08/06/2017 12:00

In a quantum fluid such as a condensed Bose gas, elementary excitations such as phonons behave as quantized fields with dispersion relations and non-linearities that bear some resemblance to those of the electromagnetic field. The very low temperatures of these gases means that in some cases quantum fluctuations are important. Several remarkable phenomena in quantum electrodynamics have found...

18. Stéphane Attal: Open Quantum Walks, Unitary Quantum Walks and in Between

08/06/2017 13:00

I shall give an introduction to Open Quantum Walks, which are a new type of quantum walks, implementing dissipation. I shall relate them to the usual (unitary) quantum walks and show that there exists a very interesting type of quantum walks interpolating in between the two. One knows very very few things about these interpolating quantum walks.

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