Upcoming seminars

Doped resonating valence bond states: a quantum information study

Seminar date and time: 
2017-06-12 14:30
Author: 
Sudipto Singha Roy
Affiliation: 
HARISH-CHANDRA RESEARCH INSTITUTE, ALLAHABAD, UTTAR PRADESH, INDIA

Abstract:

Resonating valence bond states have played a crucial role in the description of exotic

phases in strongly correlated systems, especially in the realm of Mott insulators and the

associated high­Tc superconducting phase transition. In particular, RVB states are

considered to be an important system to study the ground state properties of the doped

quantum spin­1/2 ladder. It is therefore interesting to understand how quantum correlations

are distributed among the constituents of these composite systems. In this regard, we

Location: 
GiQ's seminar room

Quantum and Information Thermodynamics: A Unifying Framework based on Repeated Interactions

Seminar date and time: 
2017-06-07 14:00
Author: 
Philipp Strasberg
Affiliation: 

In this talk I will show how to expand the standard thermodynamic framework of a system coupled to a thermal reservoir by considering a stream of independently prepared units repeatedly put into contact with the system. These units can be in any nonequilibrium state and interact with the system with an arbitrary strength and duration. We will see that this stream constitutes an effective resource of nonequilibrium free energy and identify the conditions under which it behaves as a heat, work or information reservoir.

Location: 
GIQ - Seminar room
Contact: 

Irreducible noncontextuality inequalities from the Kochen-Specker theorem

Seminar date and time: 
2017-05-31 14:30
Author: 
Ravi Kunjwal
Affiliation: 
Perimeter Institute

Recent work (Kunjwal and Spekkens, Phys. Rev. Lett. 115, 110403 (2015)) has shown how operational noncontextuality inequalities robust to noise can be obtained from Kochen-Specker uncolourable (or KS-uncolourable) hypergraphs without assuming that measurement outcomes are fixed deterministically by the ontic state of the system in an underlying ontological model. This result was obtained by an explicit numerical enumeration of all the extremal points of the polytope of (measurement) noncontextual assignments of probabilities to the KS-uncolourable hypergraph.

Location: 
GIQ seminar room C5/260

A single atom heat engine

Seminar date and time: 
2017-05-30 16:00
Author: 
Eric Lutz
Affiliation: 
University of Erlangen-Nürnberg, Germany

We review the miniaturization of heat engines towards the nanoscale. We

discuss in detail the experimental realization of a single atom engine

using an ultracold trapped ion coupled to engineered reservoirs. We

further address the question of how to enter the quantum regime and

exploit quantum effects to enhance the performance of the machine.

Location: 
GiQ's seminar room
Contact: 

Digital quantum metrology

Seminar date and time: 
2017-05-29 16:00
Author: 
Lorenzo Maccone
Affiliation: 
Universita' di Pavia, Italy

Quantum Metrology calculates the ultimate precision of all estimation

strategies, measuring what is their root mean-square error (RMSE) and

their Fisher information. Here, instead, we ask how many bits of the

parameter we can recover, namely we derive an information-theoretic

quantum metrology. In this setting we redefine "Heisenberg bound" and

"standard quantum limit" (the usual benchmarks in quantum estimation

Location: 
GiQ's seminar room

Quantum transport in Non-Markovian, strong coupling settings: bath degrees of freedom

Seminar date and time: 
2017-05-15 14:30
Author: 
Javier Cerrillo
Affiliation: 
Technische Universität Berlin

The possibility to extract full counting statistics (FCS) of transport processes in experimental settings exposes the necessity to upgrade existing simulation methods to gain access to environmental degrees of freedom. The techniques stemming from the theory of generating functions make it possible to encode all cumulants of the outcome of a specific measurement scheme in the form of a generalized density matrix.

Location: 
GIQ - Seminar room
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Recent Results on Uncertainty Relations

Seminar date and time: 
2017-04-04 14:30
Author: 
Reinhard Werner
Affiliation: 
Institut für Theoretische Physik, Leibniz Universität Hannover

Uncertainty relations come in two kinds: The more familiar type, called preparation uncertainty, captures the impossibility of preparing states that are sharp for two given observables, whereas measurement uncertainty provides quantitative bounds to the errors in any attempt to jointly measure the two. The quantitative theory requires, for each observable involved, a cost function for errors, usually a power of a metric on the outcome space.

Location: 
GIQ - Seminar room

Metrics on quantum channels: issues, fixes, applications

Seminar date and time: 
2017-03-08 12:00
Author: 
Andreas Winter
Affiliation: 
GIQ

The diamond norm on superoperators (aka 'completely bounded norm' in the Heisenberg picture) provides a natural, operationally well-motivated, and computable metric on quantum channels (cptp maps). In particular, it quantifies the optimal bias in hypothesis testing between two channels, it is given by a semidefinite programme, and it enjoys a number of good mathematical properties. It furthermore provides the natural setting when discussing continuity of channel capacities.

Location: 
GIQ - Seminar room
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Fundamental limits for cooling of linear quantum refrigerators

Seminar date and time: 
2017-02-15 15:30
Author: 
Nahuel Freitas
Affiliation: 
Departamento de Fisica, UBA & Instituto de Fisica de Buenos Aires, UBA CONICET

I study the asymptotic dynamics of a network of oscillators whose frequencies and couplings are periodically driven while coupled with a number of bosonic reservoirs. I obtain exact results for the heat currents coming into the system from each reservoir (valid beyond the usual weak coupling, weak driving or Markovian approximations). I use these expressions to rigorously prove the validity of the dynamical version of the third law of thermodynamics (Nernst unattainability principle) in this context.

Location: 
GIQ - Seminar room
Contact: 

Gaussian optimizers in quantum information

Seminar date and time: 
2017-02-15 14:30
Author: 
Giacomo De Palma
Affiliation: 
QMATH, Department of Mathematical Sciences, University of Copenhagen

We determine the p->q norms of the one-mode quantum-limited attenuator and amplifier, and prove that they are achieved by Gaussian states. The proof technique is completely new: it is based on a new logarithmic Sobolev inequality, and it can be used to determine the p->q norms of any quantum semigroup. Our result extends to noncommutative probability the seminal theorem "Gaussian kernels have only Gaussian maximizers" [Lieb, Invent. Math. 102, 179 (1990)], stating that Gaussian functions achieve the p->q norms of Gaussian integral kernels.

Location: 
GIQ - Seminar room
Contact: 

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