# Talks

Colloquium
coffee, tea, cookies at 16:15 in the main hall
Monday 16:30-17:30
Seminar room 1+2
- monthly seminars -
Wednesday 16:30 - 18:00
Seminar room 1+2
- weekly seminars -
Monday 11:00-12:00
Room 1D1
Wednesday 16:30 - 17:30
Seminar room 1D1
Thursday 14:00-15:00
Seminar room 3

## Talks in chronological order

iCal All Events
25 Sep 2017
04:30 PM

### Quantum Metrology and Quantum Nonlocality

Maciej Lewenstein, ICFO and ICREA, Barcelona, Spain

One of the most important steps in the understanding of quantum many-body systems is due to the intensive studies of their entanglement properties [1,2]. Much less, however, is known about the role of quantum nonlocality [3] in these systems. This is because standard many body observables involve correlations among few particles, while there is no multipartite Bell inequality for this scenario. In my talk I will attempt to connect challenges of quantum metrology with those of detection of quantum nonlocality in many body systems. First, I will discuss an intimate relation between entanglement in many body states and usefulness for metrology [3]. I will focus then on usefulness of random symmetric states for metrology [4]. The second part will be devoted to non-locality. In the second part, I will first discuss shortly the role of entanglement in many body systems, stressing the difference between the gapped and critical systems. I will then concentrate on the results of Refs. [6], where we provide the first examples of nonlocality detection in many-body systems using two-body correlations. To this aim, we construct families of multipartite Bell inequalities that involve only second order correlations of local observables. We then provide examples of systems, relevant for nuclear and atomic physics, whose ground states violate our Bell inequalities for any number of constituents. We identify inequalities that can be tested by measuring collective spin components, opening the way to the experimental detection of many-body nonlocality, for instance with atomic ensembles [7], systems of trapped ions [8], or atoms trapped close to nano-structured (tapered) fibers and photonic crystals [9]. Interestingly, breaking of many body Bell inequalities witnesses certain kinds of many body entanglement [10]. Most of examples will deal with symmetric states, i.e. will call for metrological applications. If time permits, we discuss non-locality in 1D spin-chains, by employing Jordan-Wigner transformation and relation to integrable and non-integrable fermionic models [11]. References [1] A. Osterloh et al., Nature 416, 608 (2002); T. J. Osborne et al., Quantum Inf. Proc. 1, 45 (2002); Phys. Rev. A 66, 032110 (2002); G. Vidal et al., Phys. Rev. Lett. 90 227902 (2003). [2] M. Lewenstein, A. Sanpera, and V. Ahufinger, “Ultracold atoms in Optical Lattices: simulating quantum many body physics”, Oxford University Press, Oxford, 2017, ISBN 978-0-19-878580-4. [3] J. S. Bell, Physics 1, 195-200 (1964). [4] R. Augusiak, J. Kolodynski, A. Streltsov, M. N. Bera, A. Acín, M. Lewenstein, Asymptotic role of entanglement in quantum metrology, Phys. Rev. A 94, 012339 (2016). [5] M. Oszmaniec, R. Augusiak, C. Gogolin, J. Kolodynski, A. Acín, and M. Lewenstein, Random bosonic states for robust quantum metrology, Phys. Rev. X 6, 041044 (2016). [6] J. Tura et al., Detecting the non-locality of quantum many body states, Science 344, 1256 (2014); J. Tura et al., Nonlocality in many-body quantum systems detected with two-body correlators, Ann. Phys. 362, 370-423 (2015). [7] K. Hammerer et al., Rev. Mod. Phys. 82, 1041 (2010). K. Eckert et al., Nature Phys. 4, 50 (2008). [8] T. Graß and M. Lewenstein, Trapped-ion quantum simulation of tunable-range Heisenberg chains, arXiv:1401.6414, EPJ Quantum Technology 2014, 1:8, doi:10.1186/epjqt8. [9] J. S. Douglas, H. Habibian, C.-L. Hung, A. V. Gorshkov, H. J. Kimble, and D. E. Chang, Quantum many-body models with cold atoms coupled to photonic crystals, Nature Photon. 9, 326-331 (2015) [10] A. Aloy et al., Device Independent Entanglement Depth Witnesses, in preparation. [11] J. Tura, G. de las Cuevas, R. Augusiak, M. Lewenstein, A. Acín,, and J. I. Cirac, Energy as a detector of nonlocality of many-body spin systems, Phys. Rev. X7, 021005 (2017)

Seminarroom 1+2+3 iCal Event
27 Sep 2017
02:00 PM

### Neural-network Quantum States

Giuseppe Carleo (ETH Zurich)

Room 1D1 iCal Event
11 Oct 2017
02:00 PM

### tba

Yevgeny Bar-Lev (Columbia University)

tba

Room 1D1 iCal Event
12 Oct 2017
04:40 PM

### WS 2017/18 - Topic: Motivation + Statistical physics (ergodicity, entropy max) + List of questions at the end

Seminarroom 1+2 iCal Event
16 Oct 2017
04:30 PM

### Gutzwiller Colloquium: Making Living Matter from the bottom up

Ramin Golestanian (University of Oxford)

There are many ways to study life, and one that is particularly appealing to physicists is regarding it as self-organized active soft matter that is away from equilibrium just the right way’’. In this Colloquium, I will discuss this notion, and provide a number of examples of how we can begin to put together simple systems - from basic ingredients that we fully understand - that would exhibit the kind of active behaviour we find in living systems. I will address the question of stability of a living system made of active components and propose a fundamentally new mechanism in which a competition between chemical signalling and cell division can determine the homeostatic conditions at the systemic level.

Seminarroom 1+2+3 iCal Event
19 Oct 2017
02:00 PM

### TBA

Inti Sodemann (MPI-PKS)

Room 1D1 iCal Event
01 Nov 2017
04:30 PM

### On the mathematical treatment of the Born-Oppenheimer approximation

Thierry Jecko (Université de Cergy-Pontoise)

In this talk, I shall review the mathematical formulation of the Born-Oppenheimer approximation and compare it to the traditional physical point of view. I shall point out some rigorous results and open questions.

Room 1D1 iCal Event