Upcoming seminars

Distinguishing generic quantum states

Seminar date and time: 
2017-09-19 14:30
Author: 
Karol Życskowski
Affiliation: 
Jagiellonian University, Cracow, Poland

Properties of random mixed states of dimension $N$
distributed uniformly with respect to the Hilbert-Schmidt measure are
investigated. We show that for large $N$, due to the concentration of measure
phenomenon, the trace distance between two random states tends to a fixed  number 
$1/4+1/\pi$, which yields the Helstrom bound on their distinguishability. To
arrive at this result we apply free random calculus and derive the symmetrized Marchenko--Pastur 
distribution. Asymptotic value for the root fidelity between two random states, 

Location: 
GIQ Seminar Room
Contact: 
michail.skoteiniotis@uab.cat

A class of asymmetric gapped Hamiltonians on quantum spin chains and its characterization

Seminar date and time: 
2017-09-06 14:30
Author: 
Yoshiko Ogata
Affiliation: 
University of Tokyo, Japan

We introduce a class of gapped Hamiltonians on quantum spin chains, which allows asymmetric edge ground states. We investigate the property, characterize it by physical conditions, and classify it.

Location: 
GIQ Seminar Room C5/262
Contact: 
michail.skoteiniotis@uab.cat

Quantum computers - is the future here?

Seminar date and time: 
2017-09-04 14:30
Author: 
Tal Mor
Affiliation: 
Technion, Israel

More than thirty years ago Feynman and Deutsch came up with the quantum computer. A decade later Peter Shor had shown the incredible power of quantum computers - for example, their ability to factorize large numbers, an ability whose technological consequences for the world of internet encryption and banking can be devastating.

Location: 
GIQ Seminar Room C5/262
Contact: 
michail.skoteiniotis@uab.cat

Geometry of Entanglement in the Bloch Sphere

Seminar date and time: 
2017-09-01 14:30
Author: 
Rotem Liss
Affiliation: 
Technion Israel

Entanglement is an important concept in quantum information, quantum communication, and quantum computing. We provide a geometrical analysis of entanglement and separability for all the rank-2 quantum mixed states: complete analysis for the bipartite states and partial analysis for the multipartite states. For each rank-2 mixed state, we define its unique Bloch sphere, that is spanned by the eigenstates of its density matrix.

Location: 
GIQ Seminar Room C5/262
Contact: 
michail.skoteiniotis@uab.cat

Interferometric Visibility and Coherence

Seminar date and time: 
2017-08-31 14:30
Author: 
Tanmoy Biswass
Affiliation: 
IISER-Kolkata, India

Recently, the basic concept of quantum coherence (or superposition) has gained a lot of renewed attention, after Baumgratz et al. [PRL 113:140401 (2014)], following ˚Aberg [arXiv:quant-ph/0612146], have proposed a resource theoretic approach to quantify it. This has resulted in a large number of papers and preprints exploring various coherence monotones, and debating possible forms for the resource theory. Here we take the view that the operational foundation of coherence in a state, be it quantum or otherwise wave mechanical, lies in the observation of interference effects.

Location: 
GIQ Seminar Room C5/262
Contact: 
michail.skoteiniotis@uab.cat

Adaptive phase estimation with two-mode squeezed-vacuum and parity measurement

Seminar date and time: 
2017-07-19 14:30
Author: 
Zixin Huang
Affiliation: 
The School of Physics; The University of Sydney

A proposed phase-estimation protocol based on measuring the parity of a two-mode squeezed vacuum state at the output of a Mach-Zehnder interferometer shows that the Cramer-Rao sensitivity is sub-Heisenberg [Phys. Rev. Lett. 104, 103602 (2010)]. However, these measurements are problematic, making it unclear if this sensitivity can be obtained with a finite number of measurements. This sensitivity is only for phase near zero, and in this region there is a problem with ambiguity because measurements cannot distinguish the sign of the phase.

Location: 
GiQ's seminar room

Quantum machine learning for quantum anomaly detection

Seminar date and time: 
2017-07-17 15:30
Author: 
Nana Liu
Affiliation: 
Centre for Quantum Technologies, National University of Singapore

Anomaly detection is used for identifying data that does not obey the `normal' data patterns and it nds diverse applications in many important areas like fraud detection, diagnoses, data cleaning and surveillance. With the advent of quantum computing and the future of quantum computing in the cloud and over the quantum internet, anomaly detection will inevitably play an important role in revealing novel or unusual patterns in communicated quantum data. Machine learning algorithms are playing pivotal roles in classical computing, including in anomaly detection.

Location: 
GIQ - Seminar room
Contact: 

Decoding Protocols for Classical Communication on Quantum Channels

Seminar date and time: 
2017-07-17 14:30
Author: 
Matteo Rosati
Affiliation: 
Scuola Normale Superiore and Istituto Nanoscienze-CNR

I discuss the transmission of classical information via quantum carriers with focus on the decoding stage. While the optimal transmission rate and encoding have been well studied in the past providing viable solutions for free-space or optical-fiber communication, a practical decoder is still difficult to design. This is due to the requirement of performing joint measurements over several transmission modes and their difficult implementation with current technology.

Location: 
GIQ - Seminar room
Contact: 

Tensor networks for quantum matter: basics, news and prospects

Seminar date and time: 
2017-06-21 14:30
Author: 
Roman Orus
Affiliation: 

Tensor network states have established themselves as the natural language based on entanglement to describe and numerically simulate quantum many-body systems. In this talk I will first provide a long introduction to what tensor network states are, as well as to some of their related numerical methods. An overall perspective on the field will also be provided. Then, I will review recent progress on this topic conducted in my group.

Location: 
GIQ - Seminar room
Contact: 

Verification of Measurement-Based Quantum Computation

Seminar date and time: 
2017-06-15 14:30
Author: 
Masahito Hayashi

Quantum computation offers a novel way of processing information and promises solution of some classically intractable problems. However, if the component of the quantum computor has some errors, it does not output a correct computation outcome. Since the quantum computor is composed of several components, the unexpected correlation causes unexpected error that cannot be corrected by error correction. To resolve this problem, we need to verify the quantum computor.

Location: 
GIQ - Seminar room

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