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## Theory of quantum gases

### Anna Minguzzi

CNRS, Laboratoire de Physique et Modélisation des Milieux Condensés, Grenoble, France

```
anna.minguzzi AT grenoble.cnrs.fr
+ 0033 04 56 38 71 33
```

### Research activities

Quantum gases are realized by advanced techniques of atom trapping and cooling, and constitute a versatile, tunable system for the exploration of extreme states of matter, in the regime where quantum mechanics plays a fundamental role.

At LPMMC we study the properties of quantum gases with the techniques of condensed matter physics. The main topics recently explored are :

### Low-dimensional correlated quantum gases

Ultracold bosons on a 1D ring trap

A novel generation of traps with ring topology has been recently built. This geometry is particularly suitable for the study of superfluidity, and stabilizes circulating states. In the limit of a very tight quasi-1D trap, we have explored the dynamical response to a moving barrier. This allows to answer questions about the concept of superfluidity in one dimension and suggests correlated bosons on tight ring traps as possible candidates to generate macroscopic superpositions of current-carrying states.

Christoph Schenke, Anna Minguzzi,Frank W.J. Hekking, “Nonadiabatic creation of macroscopic superpositions with strongly correlated 1D bosons on a ring trap”, Phys. Rev. A 84 053636 (2011)

Christoph Schenke, Anna Minguzzi,Frank W.J. Hekking, “Probing superfluidity of a mesoscopic Tonks-Girardeau gas”, Phys. Rev. A 85 053627 (2012)

Marco Cominotti, Davide Rossini, Matteo Rizzi, Frank W.J. Hekking, Anna Minguzzi,

Optimal persistent currents for ultracold bosons stirred on a ring, arXiv : 1310.0382

1D bosons in a quasiperiodic potential

Xiaolong Deng, R. Citro, A. Minguzzi, and E. Orignac, “Phase diagram and momentum distribution of an interacting Bose gas in a bichromatic lattice”, Phys. Rev. A 78 013625 (2008)

Xiaolong Deng, R. Citro, E. Orignac, A. Minguzzi and Luis Santos “ Polar bosons in one-dimensional disordered optical lattices”, Phys. Rev. B

**87**, 195101 (2013),

"Bosonization and entanglement spectrum for one-dimensional polar bosons on disordered lattices", New Journal of Physics 15 (2013) 045023

Impenetrable bosons and Bose-Fermi mixtures in a tight atomic waveguide

In the Tonks-Girardeau limit of very strong interparticle repulsions in 1D, the atoms cannot circumvent each other and the many-body Schroedinger equation can be solved exactly by mapping onto a fermionic problem. This allows to explore the details of a correlated quantum fluid subjected to an external potential and/or a time-dependent drive. We have extended the exact solution to a mixture of bosons and spin-polarized fermions, where nontrivial issues arise from the fact that the ground state has a large degeneracy.

Bess Fang, Patrizia Vignolo, Mario Gattobigio, Christian Miniatura, Anna Minguzzi, “Exact solution for the degenerate ground-state manifold of a strongly interacting one-dimensional Bose-Fermi mixture”, Phys. Rev. A 84, 023626 (2011)

Universal properties of a Tonks-Girardeau gas at finite temperature

Bosons with contact interactions display typical 1/p^4 tails in the momentum distribution, with a weigth — the Tan contact — which contains information about the two-body correlations. We have shown that, at difference from 3D strongly interacting Fermi gases, the Tan contact increases with temperature. Furthermore, our Tan’s contact result is an example of universality in strongly interacting atomic gases.

Patrizia Vignolo, Anna Minguzzi, “Universal contact for a Tonks-Girardeau gas at finite temperature”, Phys. Rev. Lett. 110, 020403 (2013)

### Exciton-Polaritons in semiconductors

First-order spatial correlations in a quasi-onedimensional polariton gas

Exciton polaritons are composite bosons realized in seminconductor materials under driven-disspative conditions. We have studied the coherence properties of quasi-onedimensional polaritons in ZnO, in collaboration with the experimental team (M. Richard, Néel Institute, Grenoble). We highlighted in particular the interplay bewteen losses and disorder in a weakly interacting polariton gas.

### Entanglement and decoherence in Bose-Josephson junctions

Generation and detection of entangled states

Bose-Josephson junctions are obtained by connecting two Bose-Einstein condensates through a « weak link » for example realized by a potential barrier. If the barrier is suddenly raised, the phase-coherence between the two condensates rapidly degrades, giving rise to spin-squeezed states and, on longer time scales, to macroscopic superpositions of phase states. These entangled states are useful for high-precision atom interferometry. We have proposed a full-counting statistics method to measure the degree of coherence between the components of the superposition.

Giulia Ferrini, Anna Minguzzi, Frank W. J. Hekking, "Detection of coherent superpositions of phase states by full counting statistics in a Bose Josephson junction", Phys. Rev. A 80, 043628 (2009)

Studies of decoherence

The two main sources of noise in the experiments are particle losses and fluctuations of the magnetic fields used to trap the atoms, denoted as « phase noise ». We have analyzed theoretically the effect of phase noise on the state of the Bose-Josephson junction, showing that macroscopic superpositions of phase states are quite robust under phase noise and could be used for high-precision atom interferometry.

Giulia Ferrini, Dominique Spehner, Anna Minguzzi, Frank W.J. Hekking, “Noise in Bose Josephson junctions : Decoherence and phase relaxation”, Phys. Rev. A 82 033621 (2010)

### Many-body physics with interacting fermions

Dynamical properties of interacting Fermi gases

We consider a two-component Fermi gas with repulsive inter-component interactions. If the interactions are increased above a certain threshold, a ferromagnetic phase of Stoner type is predicted to occur. The simplest form of ferromagnet is the one oriented along the z-direction, that is a spatial phase separation between the two components. Using a many-body approach, we have studied the dynamical properties of such system and proposed a possible signature of ferromagnetism in the spectrum of the gas.

Matteo Sandri, Anna Minguzzi, Flavio Toigo, “Dynamical spin-flip susceptibility for a stronly interacting ultracold Fermi gas”, EPL 96 66004 (2011)

### 3D Anderson localization with matter waves

A Bose-Einstein condensate expanding in a disordered potential

We have predicted that during the expansion of a Bose-Einstein in a 3D disordered potential a fraction of the atoms is Anderson localized. From the details of the expansions, it should be possible to extract the critical exponents for Anderson localization.

S.E. Skipetrov, A. Minguzzi, B. A. van Tiggelen, and B. Shapiro, “Anderson Localization of a Bose-Einstein Condensate in a 3D Random Potential”, Phys. Rev. Lett. 100 165301 (2008)

### People

PhD students :

Florian Cartarius (cotutelle with Saarland University)

Marco Cominotti

Guillaume Lang

Katharina Rojan (cotutelle with Saarland University)

Postdocs :

Former PhD students (co-directed with Frank Hekking) :

(2009-2012) Christoph Schenke now at the University of Geneva

(2008-2011) Giulia Ferrini now at LKB, Paris

(2007-2009) Nicolas Didier now at Sherbrooke University

Former Postdocs

Pablo Capuzzi now at University of Buenos Aires, Argentina

Xiaolong Deng now at Institute of Theoretical Physics, Hannover, Germany

Sanjoy Datta now at the National Institute of Technology, Rourkela, India

### Editorial Work

I am Associate Editor of New Journal of Physics

### Conference Organization

Theory of Quantum Gases and Quantum Coherence — a biannual workshop on the theory advances in quantum gases, dedicated to students, postdocs and junior researchers. The last three editions were held in France and were recognized as "CNRS Thematic School". Forthcoming edition : BEC2014 : Quantum Gases and Quantum coherence in Levico Terme (IT)

Mini-Colloquium Strongly correlated quantum gases in the Journées de la Matière Condensée JMC13 of the French Physical Society

Quantum Fluids and Solids QFS2010 Satellite Meeting Cold Gases Meet Many-Body Physics

Condensed Matter in Paris 2014 Joint Meeting of the Condensed Matter Division of the European Physical Society and of the French Physical Society JMC14/CMD25

Mini-Colloquium Mesoscopic Physics and Quantum Gases in the Journées de la Matière Condensée JMC14 of the French Physical Society

### Publications

### Short CV

2014 - : CNRS research director at LPMMC

2009 - 2014 : senior CNRS researcher at LPMMC

2005 - 2009 : CNRS researcher at LPMMC, Grenoble

2005 : Research contract at LPTMS, Orsay

2000-2004 : Research contract at SNS, Pisa

1997 - 1999 : PhD at Scuola Normale Superiore, Pisa (supervisor : Mario Tosi)

1992 - 1996 : Student at Scuola Normale Superiore in Pisa (Italy)

*Awards, distinctions*

APS outstanding Referee 2012

Distinguished EPL Referee 2011

### Animation

Member of the board of The Grenoble Center for Theoretical Physics (CPTG)

Chair of the Condensed Matter Division of the French Physical Society (SFP)