##### Workshop

#### Entanglement in Quantum Systems

**May, 21 2018 - Jul, 13 2018**

The event is partially supported by the Simons Collaboration "It from Qubit"

**Organizers**

*Pasquale Calabrese *(SISSA, Trieste)

*Ignacio Cirac *(Max Planck Institute, Garching)

*Joel Moore *(University of California, Berkeley)

*Robert Myers * (Perimeter Institute, Waterloo)

*Mukund Rangamani *(University of California, Davis)

*Tadashi Takayanagi *(Yukawa Institute, Kyoto)

*Erik Tonni *(SISSA, Trieste)

**Local organizer**

Domenico Seminara

**Contact**

etonni@sissa.it

seminara@fi.infn.it

**Related events**

Entanglement in Quantum Systems (Conference) - Jun, 04 2018

Quantum Information in Quantum Gravity 4 (Meeting) - Jun, 11 2018

Tensor Networks and Entanglement (Focus Week) - Jun, 18 2018

**Abstract**

Understanding the nature of entanglement in quantum systems has been an important challenge in theoretical physics since the early days of quantum mechanics. However, it is only during the last decade that entanglement became a powerful tool to characterize extended quantum systems. Various aspects of quantum entanglement have been studied by employing the most advanced methods available in Quantum Field Theory, Quantum Gravity, Condensed Matter and Quantum Information. Despite the great achievements, many important theoretical questions are still unanswered and it is nowadays evident that an interdisciplinary effort is necessary to find satisfactory solutions.

The aim of this workshop is bringing together a broad spectrum of theorists who have a strong expertise in the areas of Quantum Field Theory, Quantum Gravity, Condensed Matter Theory and Quantum Information, including also some experimentalists, in order to exchange knowledge and discuss open problems related to entanglement from different perspectives.

**Topics**

- Entanglement measures in Quantum Field Theories

- Entanglement in many-body systems

- Entanglement in Quantum Gravity: gravitational constraints and emergence of spacetime

- Role of entanglement in Quantum Information

- Tensor networks and entanglement

- Experimental detection of entanglement

**ACRI fellowships**

Individual fellowships are available for young researchers funded by ACRI under the “Young Investigator Training Program 2017”. The fellowship supports a scientific visit of at least one month in Italy: it provides 3000 euro for researchers from Europe or 4000 euro for those from outside Europe. The visit must include the attendance of the program “Entanglement in Quantum Systems” at GGI for at least two weeks. The remaining time must be spent in another research institute in Italy among the ones selected for this program, which are listed here, together with the corresponding contact person, who must approve the visit. A CV and a research statement including the chosen research institute and the reasons for this choice must be sent by email to Erik Tonni. The deadline is February 15, 2018.

**Preview**

**Poster sessions**

Poster sessions will be organised during the three events (main conference, QIQG4 meeting and tensor network focus week). The participants who would like to present a poster are kindly invited to send an email with the title and a short abstract to Erik Tonni before May 16, specifying also in which event(s) they want to make their presentation. Since a limited number of panels is available, the organisers will select the presentations shortly after the deadline. The poster panels will also be available even during the program, therefore the participants who wants to show a poster during their stay even outside the three key events are kindly invited to follow the above procedure.

**Talks**

May, 22 2018 - 15:00 | Tatsuma Nishioka | OPE for Conformal Defects and Holography | Talk | |||||

May, 23 2018 - 11:30 | Tomonori Ugajin | Relative entropy in CFT | Talk | |||||

May, 24 2018 - 15:00 | Romuald Janik | Exact Matrix Product State for the Klein-Gordon bosonic chain | Talk | |||||

May, 25 2018 - 11:30 | Djordje Radicevic | Flux-attached gauge theories and topological entanglement entropy | Talk | |||||

May, 28 2018 - 15:00 | Benjamin Doyon | Emergent hydrodynamics in integrable systems out of equilibrium | Talk | I will introduce the recently developed theory of "generalized hydrodynamics" (GHD). This describes large-scale behaviours in many-body quantum and classical integrable systems out of equilibrium - in inhomogeneous states and force fields - by adapting the principles of hydrodynamics to the presence of infinitely many conservation laws. I will then cover one or more of the following topics: how GHD can be used to describe cold atom gases in one-dimensional settings and theoretically solve the famous quantum Newton cradle experiment; how it predicts the validity of conventional hydrodynamics at zero temperature before shocks appear and prevents shock formations; how it describes classical systems such as the hard rod gas, soliton gases and the gases of classical field radiations; how it gives rise to Euler-scale correlation functions, Drude weights, and scaled cumulant generating functions (non-equilibrium current, zero-frequency noise, full counting statistics) for non-equilibrium transport; what the underlying geometry is; some GHD exact solutions and numerical techniques. | ||||

May, 29 2018 - 15:00 | Giuseppe Policastro | Holographic complexity and defect CFT | Talk | Recently the concept of complexity has been proposed by Susskind as a measure of the more subtle properties of information processing in the context of black holes physics, and a conjecture on how to measure this quantity in the holographic correspondence was put forward. It still remains to be proven, however, that the complexity can be a useful and well-defined concept in quantum field theory. I will describe this developments, then present our calculation of the complexity for a conformal field theory in presence of a defect. | ||||

May, 30 2018 - 15:00 | Paul Fendley | Baxterising using topological defects and conserved currents | Talk | Many integrable critical classical statistical mechanical models and the corresponding quantum spin chains possess an unusual sort of conserved current, built by terminating a topological defect. Such currents have been constructed by utilising quantum-group algebras, fermionic and parafermionic operators, and ideas from ``discrete holomorphicity''. I define them generally and naturally using a braided tensor category, a structure familiar from the study of knot invariants and from conformal field theory. Requiring the existence of the currents provides a simple way of ``Baxterising'', i.e. building a solution of the Yang-Baxter equation out of topological data. This approach allows many new examples of conserved currents to be found, for example in height models. Although integrable models found by this construction are critical, I find one non-critical generalisation: requiring a ``shift'' operator in the chiral clock chain yields precisely the Hamiltonian of the integrable chiral Potts chain. | ||||

May, 31 2018 - 11:30 | David Perez Garcia | Bulk-boundary correspondence in PEPS | Talk | |||||

May, 31 2018 - 15:00 | Tommaso Roscilde | Finding entanglement in a path integral | Talk | Certifying and analyzing the entanglement content of quantum mixed states is a most important challenge for theory and experiments alike. In the absence of unambiguous entanglement estimators for mixed states, a valid alternative approach is the formulation of entanglement witnesses, aimed at detecting the non-separability and the entanglement pattern of the largest possible class of entangled density matrices. This approach has recently experienced very important advances, thanks to the discovery that quantum coherence estimators, certifying the non-diagonal nature of the quantum state on the eigenbasis of a given observables, can act as effective entanglement witnesses. In this seminar I shall discuss how fundamental information on quantum coherence can be extracted from standard tools in quantum statistical physics. Quantum coherence is encoded in the imaginary-time evolution of observables; and it can be quantified geometrically within a path-integral representation of the quantum state, by estimating the variance of imaginary-time fluctuations. Such a variance has an immediate physical meaning, as the difference between fluctuations and susceptibility of an observable. This framework offers very powerful tools for entanglement witnessing in all the models whose equilibrium statistical physics can be quantitatively reconstructed, either analytically or numerically. I shall illustrate a few applications to models in the vicinity of a quantum critical point. | ||||

Jun, 01 2018 - 15:00 | Clement Berthiere | Boundary contribution to (holographic) entanglement entropy | Talk | The entanglement entropy, while being under the spotlight of theoretical physics for more than ten years now, remains very challenging to compute, even in free quantum field theories, and a number of issues are yet to be explored. One such issues concerns boundary effects on entanglement entropy, which is important both for theoretical explorations of entanglement and for applications of entanglement entropy to lattice simulations, condensed matter systems, etc.. During this talk, I will show how the presence of spacetime boundaries affects the entanglement entropy, with emphasize on universal (boundary-induced) logarithmic terms, using field theoretic, lattice, and holographic methods. |