Upcoming seminars

Quantum State Redistribution for Ensemble Sources

Seminar date and time: 
2020-11-05 16:15
Author: 
Zahra Baghali Khanian
Affiliation: 
GIQ

We consider a generalization of the quantum state redistribution task, where pure multipartite states from an ensemble source are distributed among

an encoder, a decoder and a reference system. The encoder, Alice, has access to two quantum systems: system $A$ which she compresses and sends to the decoder,

Bob, and the side information system $C$ which she wants to keep at her site. Bob has access to quantum side information in a system $B$, wants to decode

the compressed information in such a way to preserve the correlations with the reference system on average.

Location: 
GIQ VIRTUAL SEMINAR
Contact: 

General Mixed State Quantum Data Compression with and without Entanglement Assistance

Seminar date and time: 
2020-11-03 11:00
Author: 
Zahra Baghali Khanian
Affiliation: 
GIQ

We consider the most general (finite-dimensional) quantum mechanical information source, which is given by a quantum system

$A$ that is correlated with a reference system $R$. The task is to compress $A$ in such a way as to reproduce the joint source state

$\rho^{AR}$ at the decoder with asymptotically high fidelity. This includes Schumacher's original quantum source coding problem of a

pure state ensemble and that of a single pure entangled state, as well as general mixed state ensembles.

Location: 
GIQ VIRTUAL SEMINAR
Contact: 
zbkhanian@gmail.com

Non-Equilibrium Biomagnetic Sensing: Three Radical Mechanism in Cryptochrome

Seminar date and time: 
2020-10-28 12:00
Author: 
Nathan Babcock
Affiliation: 
University of Exeter

Migratory birds' visual magnetic sense is believed to rely on radical pair reactions in proteins, to enable them to sense weak magnetic fields below the thermodynamic limit. In this model, magnetic sensitivity originates from the interplay between coherent spin dynamics and recombination kinetics, as the radicals couple to the magnetic field via nuclear hyperfine interactions. However, prior studies have often neglected the effect of electron-electron dipolar (EED) coupling from this hypothesis.

Location: 
GIQ Seminar Room
Contact: 
nbabcock@gmail.com

Statistical properties of the quantum internet

Seminar date and time: 
2020-03-27 12:00
Author: 
Daniel Calvacanti
Affiliation: 
ICFO, Barcelona

Steady technological advances are paving the way for the implementation of the quantum internet, a network of locations interconnected by quantum channels. In this talk I will describe a model to simulate a quantum internet based on optical fibers and employ network-theory techniques to characterize the statistical properties of the photonic networks it generates. This model predicts (i) a phase transition between a disconnected and a highly-connected phase, (ii) that the typical photonic networks do not present the small world property, but that (iii) they are highly aggregated.

Location: 
GIQ Seminar Room
Contact: 
Daniel.Cavalcanti@icfo.eu

What is heat?: micro-reversibility and thermalization in collisional thermal baths

Seminar date and time: 
2020-03-13 12:00
Author: 
Juan M. R. Parrondo
Affiliation: 
Universidad Complutense de Madrid

The usual model for collisional thermal baths consists of a system interacting with small units drawn from a reservoir. The interaction must be switched on and off and this operation can involve the exchange of energy between the system and the external agent that connects and disconnects the interaction, and this energy has been considered work.

Location: 
GIQ Seminar Room
Contact: 
parrondo@fis.ucm.es

Faster ground state preparation and high-precision ground energy estimation with fewer qubits

Seminar date and time: 
2020-03-06 14:00
Author: 
Jordi Tura i Brugués
Affiliation: 
Max Planck Institute, Garching

We propose a general-purpose quantum algorithm for preparing ground states of quantum Hamiltonians from a given trial state. The algorithm is based on techniques recently developed in the context of solving the quantum linear systems problem [Childs, Kothari, Somma'15]. We show that, compared to algorithms based on phase estimation, the runtime of our algorithm is exponentially better as a function of the allowed error, and at least quadratically better as a function of the overlap with the trial state.

Location: 
GIQ Seminar Room
Contact: 
jordi.tura@mpq.mpg.de

Flexible quantum state tomography

Seminar date and time: 
2020-03-06 12:30
Author: 
Daniel Uzcátegui Contreras
Affiliation: 
Universidad de Antofagasta, Chile

We present an efficient algorithm that solves the quantum state tomography problem from an arbitrary number of projective measurements in any finite dimension d. The algorithm is flexible enough to allow us to impose any desired rank r to the state to be reconstructed, ranging from pure (r=1) to full rank (r=d) quantum states. The method exhibits successful and fast convergence under the presence of realistic errors in both state preparation and measurement stages, and also when considering overcomplete sets of observables.

Location: 
GIQ Seminar Room
Contact: 
danuzco@gmail.com

Gaussian Thermal Operations and The Limits of Algorithmic Cooling

Seminar date and time: 
2020-02-21 16:00
Author: 
Gerardo Adesso
Affiliation: 
University of Nottingham

The recently established resource theory of quantum thermodynamics offers a framework to determine the ultimate possibilities and limitations in the manipulation of quantum states and in the implementation of nanoscale thermal machines. A core endeavour of this programme is to determine under which conditions can a nonequilibrium quantum state be converted into another using thermal operations. Here we settle this question in the important case of Gaussian quantum states and channels.

Location: 
Contact: 

PhD Defense: The Theory of Quantum Coherence

Seminar date and time: 
2020-02-21 11:00
Author: 
María García Díaz
Affiliation: 
Universitat Autonoma de Barcelona

Quantum coherence, or the property of systems which are in a superposition of states yielding interference patterns in suitable experiments, is the main hallmark of departure of quantum mechanics from classical physics. Besides its fascinating epistemological implications, quantum coherence also turns out to be a valuable resource for quantum information tasks, and has even been used in the description of fundamental biological processes.

Building Multiple Access Channels with a Single Particle

Seminar date and time: 
2020-02-19 15:00
Author: 
Eric Chitambar
Affiliation: 
University of Illinois

A multiple access channel describes a situation in which multiple senders are trying to forward messages to a single receiver using some communication medium. In this talk we consider scenarios in which this medium consists of just a single classical or quantum particle. In the quantum case, the particle can be prepared in a superposition state thereby allowing for a richer family of encoding strategies.

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