Taming, slowing and trapping atoms with light
Cold is quantum, Quantum is cool!
We shape quantum matter
Multicolored lasers for a variety of atoms
Keeping our eyes on the quantum world
Join our ultracool group!
High technology for great science

Welcome to the website of the Ultracold Quantum Gases group at the European Laboratory for Nonlinear Spectroscopy (LENS), the Department of Physics and Astronomy of the University of Florence (Italy) and the Institute of Optics of the Italian National Research Council (CNR - INO). In our labs we use lasers and magnetic fields to produce the lowest temperatures of the Universe, just a few billionths of a degree above absolute zero...

At these temperatures, atoms stop moving and we can control them for a variety of different fundamental studies and applications. We can force atoms to arrange according to a periodic structure and simulate the behavior of crystalline solids and new materials. We can use the atoms as ultra-high accurate sensors to probe forces with the power of quantum mechanics. We can study how quantum particles combine together under the action of strong interactions and how superfluidity develops. We can use these ultracold atoms to process information and develop new quantum technologies.

Dress warmly and... follow us for this ultracold journey!


A novel heterogeneous phase in strongly repulsive Fermi gases

Despite its seeming simplicity, a Fermi gas of ultracold atoms with strong repulsive interactions exhibits a complex behavior, resulting from the competing action of two distinct instabilities — ferromagnetism and pairing. The breakdown of the repulsive Fermi liquid state, arising from such concurrent mechanisms, has been recently observed in real time through pump-probe spectroscopic techniques [A. Amico et al., Phys. Rev. Lett. 121, 253602 (2018)], leading also to the discovery of an emergent metastable microemulsion state of anticorrelated fermions and pairs. Here, we investigate the properties of such correlated many-body regime by preparing a strongly repulsive Fermi gas, and studying the evolution of kinetic and release energies, of the spectral response and coherence of the unpaired fermionic population, and of its spin-density noise correlations. All our observations consistently point to a low-temperature heterogeneous phase, where paired and unpaired fermions macroscopically coexist while exhibiting microscale inhomogeneity. Our findings open the exploration of quantum emulsions and possibly of inhomogeneous superfluid regimes.

F. Scazza et al.
Exploring emergent heterogeneous phases in strongly repulsive Fermi gases
Phys. Rev. A 101, 013603 (2020)

Lee-Huang-Yang energy for heteronuclear mixtures

We show that the Lee-Huang-Yang (LHY) energy functional for a heteronuclear Bose mixture can be accurately approximated by an expression that has the same functional form as in the homonuclear case. It is characterized by two exponents, which can be treated as fitting parameters. We demonstrate that the values of these parameters which preserve the invariance under permutation of the two atomic species are exactly those of the homonuclear case. Deviations from the actual expression of LHY energy functional are discussed quantitatively.

F. Minardi et al.
Effective expression of the Lee-Huang-Yang energy functional for heteronuclear mixtures
Phys. Rev. A 100 063636 (2019)

Quantum Droplets in a Heteronuclear Bose Mixture observed

We report on the formation of heteronuclear quantum droplets in an attractive bosonic mixture of 41K and 87Rb. We observe long-lived self-bound states, both in free space and in an optical waveguide. In the latter case, the dynamics under the effect of a species-dependent force confirms their bound nature. By tuning the interactions from the weakly to the strongly attractive regime, we study the transition from expanding to localized states, in both geometries. We compare the experimental results with numerical simulations and we find a good agreement in the full range of explored interactions.

C. D'Errico et al.
Observation of Quantum Droplets in a Heteronuclear Bosonic Mixture
Phys. Rev. Research 1, 033155 (2019)

Understanding Josephson tunneling in strongly interacting Fermi superfluids in the simplest way!

Together with Wilhelm Zwerger, we developed a simple analytic model to quantitatively describe the Josephson tunneling between two Fermi superfluids along the entire BCS-BEC crossover. Our work just got published in Phys. Rev. A.

M. Zaccanti, W. Zwerger,
Critical Josephson current in BCS-BEC–crossover superfluids
Phys. Rev. A 100, 063601 (2019)

Quantum Zeno-assisted Noise Sensing

The ideal quantum Zeno effect is a robust method to protect the coherent dynamics of a quantum system. In particular , in the weak quantum Zeno regime, repeated quantum projective measurements can allow the sensing of semi classical field fluctuations. We report our proposal and demonstration, both theoretical and experimental, of a novel noise sensing scheme enabled by the weak quantum Zeno regime. We experimentally tested these theoretical results on a Bose Einstein Condensate of 87Rb atoms realized on an atom chip, by sensing ad hoc introduced noisy fields.

H.–V. Do et al.,
Experimental proof of quantum Zeno-assisted noise sensing
New J. Phys. 21, 113056 (2019)

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