Upcoming seminars

Activation of genuine multipartite entanglement: beyond the single-copy paradigm of entanglement characterisation

Seminar date and time: 
2021-09-23 16:00
Author: 
Simon Morelli
Affiliation: 
IQOQI Vienna

Entanglement shared among multiple parties presents complex challenges for the characterisation of different types of entanglement. One of the most basic insights is the fact that some mixed states can feature entanglement across every possible cut of a multipartite system, yet can be produced via a mixture of partially separable states. To distinguish states that genuinely cannot be produced from mixing partially separable states, the term genuine multipartite entanglement was coined.

Location: 
https://us02web.zoom.us/j/83410362610?pwd=VkJrVENrTmRSL1NBU3BZeXBmS1RQdz09
Contact: 

Testing the quantumness of gravity via a mathematical theory of quantum benchmarks

Seminar date and time: 
2021-09-16 16:00
Author: 
Ludovico Lami
Affiliation: 
Ulm University

Given a system of massive quantum harmonic oscillators, how can we test whether their gravitational interaction is classical or quantum? Here we propose a general Gedankenexperiment to do so and benchmark it, i.e. we show how to determine the threshold beyond which one can claim that gravity behaves as a quantum interaction Hamiltonian instead of a classical field. The remarkable aspect of our approach is that it bypasses completely the problem of how a classical gravitational field may interact with the quantum oscillators.

Location: 
https://us02web.zoom.us/j/84464822440?pwd=a2xQREM2ZjBQdVlyK2NkdE8zU253Zz09
Contact: 

Information geometry, asymptotic normality and metrology for quantum input-output systems

Seminar date and time: 
2021-06-10 16:00
Author: 
Madalin Guta
Affiliation: 
University of Nottingham, UK

Markov theory plays a central role in the study of open quantum systems. In this presentation I will discuss the problem of identifying and estimating dynamical parameters of quantum Markov processes, in the input-output formalism. I will consider several aspects of this problem: The first one concerns the structure of the space of identifiable parameters for ergodic dynamics, assuming full access to the output state for arbitrarily long times. The second aspect concerns the information geometric structure on this space.

Location: 
https://us02web.zoom.us/j/88343510649?pwd=cmVnWnpXMHBJdUJScVhOQWRydFR3Zz09

Choquet's theorem for constrained sets of quantum states

Seminar date and time: 
2021-06-03 16:00
Author: 
Stephan Weis
Affiliation: 
Berlin

Quantum technology is creating an increasing research activity in information theory, engineering, and physics. One example is the theory of quantum channels with input constraints. This line of research has seen new results in quantum communication theory and quantum dynamics, but its basic functional analysis is still unexplored. Here, we provide a version of Choquet’s theorem regarding constrained sets of states. The result simplifies the definitions of several characteristics of quantum information theory.

Location: 
https://us02web.zoom.us/j/84461611392?pwd=a09tNUVwYkZDb2plM0ZSSEpweUF4Zz09

From Static to Dynamic Divergences

Seminar date and time: 
2021-05-27 16:00
Author: 
Gilad Gour
Affiliation: 
University of Calgary, AB, Canada

In this talk I will introduce an axiomatic approach for channel divergences and channel relative entropies that is based on three information-theoretic axioms of monotonicity under superchannels (i.e. generalized data processing inequality), additivity under tensor products, and normalization. I will show that these axioms are sufficient to give enough structure, leading to numerous properties that are applicable to all channel divergences. These include faithfulness, continuity, a type of triangle inequality, and boundedness between the min and max channel relative entropies.

Location: 
https://us02web.zoom.us/j/82570810222?pwd=TUhTemJCZy9leHlMdDNZSHloeWh2QT09

Quantum operations with indefinite direction of time: the quantum time flip

Seminar date and time: 
2021-05-20 10:00
Author: 
Giulio Chiribella
Affiliation: 
University of Hong Kong

The standard operational framework of quantum theory is time-asymmetric. This asymmetry reflects the capabilities of ordinary agents, who are able to deterministically pre-select the states of quantum systems, but not to deterministically post-select the outcomes of quantum measurements. However, the fundamental dynamics of quantum particles is time-symmetric, and is compatible with a broader class of operations where pre-selections and post-selections are combined in general ways that do not presuppose a definite direction of time.

Location: 
https://us02web.zoom.us/j/83095734619?pwd=MG5VN1pPVjNUbVM5S1dZVm1nbC9TQT09

Strict hierarchy between parallel, sequential, and indefinite-causal-order strategies for channel discrimination

Seminar date and time: 
2021-05-06 16:00
Author: 
Jessica Bavaresco
Affiliation: 
IQOQI, Austrian Academy of Sciences, Vienna

We will discuss a tester formalism for the task of minimum-error channel discrimination that encompasses both standard parallel and sequential strategies and indefinite-causal-order strategies. We start by applying it to general channels, and discover an instance of a discrimination task of two qubit-qubit channels, an amplitude-damping and a bit-flip channel, for which a sequential strategy outperforms any parallel strategy.

Location: 
https://us02web.zoom.us/j/82048989218?pwd=aW0rYjA2L3dZd3ZQcGJ3L1o2NUUzQT09

Beyond-classical quantum computing

Seminar date and time: 
2021-04-29 16:00
Author: 
Sergio Boixo
Affiliation: 
Google Quantum AI

I’ll review what is the current state of quantum computing with superconducting qubits.​ ​I’ll explain several experiments from Google’s Quantum AI group, including an article published in Nature in 2019 in which we carried out a computational task on an experimental quantum processor vastly outperforming current supercomputers. I will conclude with various projections on the expected advances in quantum computing in the next ten years.

Location: 
https://us02web.zoom.us/j/86846893586?pwd=TVpwM1E4cEtRYXJJNGR2YTUvSE9RZz09

On verifying quantum computations and the detection of entanglement

Seminar date and time: 
2021-04-15 16:00
Author: 
Barbara Kraus
Affiliation: 
University of Innsbruck

In this talk I will discuss several protocols designed for the verification and the characterization of quantum devices. In the first part of the talk I will focus on the purely classical verification of the output of a quantum computer and will present a minimal example for realizing such a verification protocol with current technology. In the second part I present experimentally accessible conditions for detecting entanglement

Location: 
https://us02web.zoom.us/j/82487958418?pwd=d0t5NFV2UnJBQUNnbFc3UnNtTWVQQT09

The quantum marginal problem

Seminar date and time: 
2021-04-08 16:00
Author: 
Otfried Gühne
Affiliation: 
University of Siegen

The quantum marginal problem

Clarifying the relation between the whole and its parts
is crucial for many problems in science. In quantum
mechanics, this question manifests itself in the quantum
marginal problem, which asks whether there is a global pure
quantum state for some given marginals. This problem arises
in many contexts, ranging from quantum chemistry to entanglement
theory and quantum error correcting codes.

Location: 
https://us02web.zoom.us/j/87045621889?pwd=Vnd6Kys3UzcyTUZ1TGd2a0pCblU4UT09

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