Upcoming seminars

Interconversion of pure Gaussian states requiring non-Gaussian operations

Seminar date and time: 
2015-10-27 14:30
Author: 
Michael Jabbour
Affiliation: 
ULB

We analyze the conditions under which local operations and classical communication enable entanglement transformations between bipartite pure Gaussian states. A set of necessary and sufficient conditions had been found [G. Giedke et al., Quant. Inf. Comput. 3, 211 (2003)] for the interconversion between such states that is restricted to Gaussian local operations and classical communication. Here, we exploit majorization theory in order to derive more general (sufficient) conditions for the interconversion between bipartite pure Gaussian states that goes beyond Gaussian local operations.

Thermometry of arbitrary quantum systems via non-equilibrium work distributions

Seminar date and time: 
2015-10-20 15:15
Author: 
Mark Mitchison
Affiliation: 
Oxford

Estimating the temperature of a cold quantum system is difficult. Usually, one measures a well-understood thermal state and uses that prior knowledge to infer its temperature. In contrast, we introduce a method of thermometry that assumes no knowledge of the state of a system and is potentially non-destructive. Our method uses a universal temperature-dependence of the non-equilibrium dynamics of an initially thermal system coupled to a qubit probe that follows from the Tasaki-Crooks theorem for non-equilibrium work distributions.

Location: 
IFAE Seminar room

Measurement-based Formulation of Quantum Heat Engine and Optimal Efficiency with Finite-Size Effect

Seminar date and time: 
2015-10-20 14:30
Author: 
Hiroyasu Tajima

Today, theoretic analysis about quantum-scale heat engines is achieving a splendid success. They clarify that the average performance of these small-size heat engines obeys the second law of the macroscopic thermodynamics[1,2], and that the single-shot performance of the heat engines obeys different rules[3,4]. They also clarifies the thermodynamic laws for information processing [5,6].

 

Location: 
IFAE Seminar room

Which discrete states have a continuum limit?

Seminar date and time: 
2015-09-29 14:30 to 15:30
Author: 
Gemma de las Cuevas
Affiliation: 
MPQ

Renormalization to low energies is widely used in condensed matter theory to reveal the low energy degrees of freedom of a system, or in high energy physics to cure divergence problems. Here we ask which states can be seen as the result of such a renormalization procedure, that is, which states can be “renormalized to high energies". Intuitively, the continuum limit is the limit of this "renormalization" procedure. We consider two definitions of continuum limit and characterise which states satisfy either one in the context of Matrix Product States. (Joint work with N. Schuch, D.

Location: 
IFAE seminar room

Monogamy equalities for qubit entanglement from Lorentz invariance

Seminar date and time: 
2015-09-22 14:30
Author: 
Jens Siewert
Affiliation: 
Bilbao

A striking result from nonrelativistic quantum mechanics is the
monogamy of entanglement, which states that a particle can be
maximally entangled only with one other party, not with several ones.
While there is the exact quantitative relation for three qubits and
also several inequalities describing monogamy properties it has not
been clear to what extent exact monogamy relations are a general feature
of quantum mechanics. We show that in all many-qubit systems
there exist strict monogamy laws for quantum correlations.

Location: 
IFAE seminar room

Extreme finite size effects

Seminar date and time: 
2015-09-17 14:30
Author: 
Angelo Lucia

 The standard approach for describing and analysing macroscopic properties of physical systems is to consider a family of many-body quantum Hamiltonians defined on an increasing sequence of finite lattices, and then look for properties, like the groundstate degeneracy or the energy gap between the groundstate and the first excited states, that are satisfied uniformly for all system sizes large enough. This idea is at the core of the mathematical definition of thermodynamic limit, and is how most experiments (either numerical or in a lab) are carried over.

Relaxations of Graph Isomorphism

Seminar date and time: 
2015-09-16 15:05
Author: 
David Roberson

We introduce a two player non-local game based on graph isomorphisms. The input for the game is two graphs X and Y, and players attempt to convince a referee that there exists an isomorphism between X and Y. Classically, players can win this game with probability one if and only if a corresponding isomorphism does in fact exist. It is then natural to ask what happens when the players are allowed to make quantum measurements on a shared entangled state, i.e. are permitted to use "quantum strategies".

Logit Dynamics for Local Interaction Games

Seminar date and time: 
2015-09-16 14:30
Author: 
Diodato Ferraioli

The logit choice function is a family of randomized best response functions
parametrised by beta, the inverse noise level, which is used to model
players with limited rationality and knowledge [D. McFadden - Frontiers in
Econometrics, 1974]. We study the behavior of a game when players update
their strategies according to the logit choice function. We focus on two
extremal case: when at each step only one randomly chosen player is allowed
to update and when at each time step players concurrently update.

Location: 
IFAE seminar room

The role of coherences in quantum thermodynamics

Seminar date and time: 
2015-07-23 15:30
Author: 
Giovanni Vacanti

In the context of quantum thermodynamics (QT), it is important to determine which states of a given system have genuine quantum features. In this regard, the concept of asymmetry with respect to time translation can be used to distinguish classical states from quantum states. Loosely speaking, while it might be possible to interprete the thermodynamic properties of states that are symmetric with respect to time translation (i.e.

Location: 
IFAE seminar room

Experimental high-dimensional multipartite entanglement with twisted photons

Seminar date and time: 
2015-07-23 14:30
Author: 
Mehul Malik
Affiliation: 
IQOQI

Initially proposed as a two-particle problem, the concept of entanglement was extended to three particles by Greenberger, Horne, and Zeilinger in 1989. To date, experimental realizations of multipartite states have been limited to two dimensions due to the use of polarization-entangled photons. When the dimensionality of such states is increased, a richer entanglement structure emerges, where the dimensionality of each component particle can be different. The orbital angular momentum (OAM) of photons offers a discrete, high-dimensional Hilbert space for realizing such states.

Location: 
IFAE seminar room
Contact: 
Marcus Huber

Pages

Campus d'excel·lència internacional U A B