QUIT mini workshop on QUantum Information in Thermodynamics

QUIT mini workshop on QUantum Information in Thermodynamics

Seminar author:Marcus Huber

Event date and time:12/03/2014 02:00:pm

Event location:IFAE Seminar Room

Event contact:

 

Program:
14:00 Christian Gogolin (ICFO): “Equilibration and thermalization in quantum systems“
14:35 Lídia del Rio (Bristol): “Resource theories for thermodynamics: review and generalizations“
15:10 Martí Perarnau-Llobet (ICFO): “Correlating thermal states: Limitations and costs“
15:45 COFFEE BREAK
16:30 John Goold (ITP Trieste): “Steps towards experimental demonstration of information to energy conversion in a quantum system at the Landauer limit“
17:05 Luis Correa (UAB): “Individual quantum probes for optimal thermometry“
17:40 More coffee and open discussion(s)
19:00 Leaving UAB together for pre-dinner apéritif
21:00 Surprise dinner in Barcelona

Participation is completely free of charge, but to avoid wastefulness in resources we would ask:
In case you intend to attend please send an email to marcus.huber@uab.cat indicating also if you’d like to join the dinner (which we will not be able to pay for). This would help us order the appropriate amount of coffee, cookies and cakes and to reserve sufficient space for the dinner.

Abstracts:

Christian Gogolin (ICFO): “Equilibration and thermalization in quantum systems“
In this talk I show how finite dimensional quantum systems in pure states that evolve unitarily according to the Schrödinger equation can exhibit thermodynamic behavior. More precisely, I will discus conditions under which equilibration and thermalization can be ensured in such systems and show that a lack of  entanglement in the energy eigenbasis can prevent thermalization. Finally I present rigorous results on structural properties of thermal states of locally interacting quantum systems that imply lower bounds on the critical temperatures below which such systems can exhibit phases with long range order.

Lídia del Rio (Bristol): “Resource theories for thermodynamics: review and generalizations“
In the first part of the talk, I will review recent approaches to thermodynamics as a resource theory.  We will discuss assumptions and limitations, not always explicit, of different theories.
In the second part, I introduce a general framework for resource theories, and discuss applications to thermodynamics. This framework allows us to analyse different aspects of thermodynamics independently, and helps understand the origin of familiar features of the theory. For instance, what impact does it have to change the structure of the state space from classical to quantum mechanics? How do the laws of thermodynamics look if, instead of energy conservation, we impose other physical constraints on the allowed transformations? We can also model the knowledge of an agent acting on a system explicitly, and see how it affects the cost of  state transformations in different settings.

Martí Perarnau-Llobet: “Correlating thermal states: Limitations and costs“
In this talk we will consider the issue of correlating quantum states at non-zero temperature. First, we will discuss how the initial temperature limits the amount of (quantum) correlations. In particular, we will characterize the maximal temperature that allows for the creation of genuine quantum correlations (i.e., entanglement). It will be shown that both entanglement and genuine multipartite entanglement can be created at high temperatures, as long as we have enough copies of the states. Second, we will consider the energy cost of correlating thermal states. We will determine the optimal protocol for generating correlations (as quantified by the mutual information) in a bipartite system at minimal energy cost, leading to a linear interconversion of energy into correlations. Such a protocol is surprisingly simple and applies to any bipartite system. On the other hand, the optimal protocol for entanglement generation highly depends on the systems of interest, and we will discuss the cases of bosonic and fermionic systems. This talk is based on arxiv.org/abs/1409.4647 and arxiv.org/abs/1404.2169.

John Goold (ITP Trieste): “Steps towards experimental demonstration of information to energy conversion in a quantum system at the Landauer limit“
Using concepts and ideas from stochastic thermodynamics several experiments have explored the thermodynamics of information processing at the ultimate limit set by Landauer. In this approach to thermodynamics quantities such as heat and work are described stochastically as fluctuations about average values  dominate physics. Turning towards quantum systems no such experiments are yet in operation. This is primarily due to the additional fragility associated with performing measurements on quantum systems. Very recently, interferometric methods have been proposed and used to measure the full statistics of work performed by replacing the necessity of projective measurements by performing phase estimation on an appropriately coupled ancilla qubit. In this talk I will outline how these schemes are modified to allow the extraction of statistics of heat dissipated from an elementary operation on a quantum system has been  performed. I will also discuss preliminary experimental results and interesting theoretical extensions.

Luis Correa (UAB): “Individual quantum probes for optimal thermometry“
The unknown temperature of a sample may be estimated with minimal disturbance by putting it in thermal contact with an individual quantum probe. If the interaction time is sufficiently long so that the probe thermalizes, the temperature can be read out directly from its steady state. Here we prove that the optimal quantum probe, acting as a thermometer with maximal thermal sensitivity, is an effective two-level atom with a maximally degenerate excited state. When the total interaction time is insufficient to produce full thermalization, we optimize the estimation protocol by breaking it down into sequential stages of probe preparation, thermal contact and measurement. We observe that frequently interrogated probes initialized in the ground state achieve the best performance. For both fully and partly thermalized thermometers, the sensitivity grows significantly with the number of levels, though optimization over their energy spectrum remains always crucial.