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!


Nowadays the need of processing large amount of data is considerably increasing, and the development of supercomputers has further encouraged the advancement of Quantum Technologies and the study of algorithms in that direction. In particular, the introduction of Quantum Machine Learning algorithms has provided a remarkable speed-up over their classical counterparts. However, the natural structure of the original data can be very complex and an intensive preprocessing is often necessary for Machine Learning algorithms to perform efficiently. In the case of binary classification problems, one would aim at achieving a geometrical representation of the data in which they are easier to be identified into distinct categories later to be analyzed.
In this context, we have developed an extensive experimental study of Quantum Embedding implementing the ideas proposed by Lloyd et al on two different experimental platforms based on ultra-cold atoms and quantum optics respectively. We perform also a similar analysis on the Rigetti superconducting quantum computer. The embedding protocol concerns a novel approach to perform classification in the context of Quantum Metric Learning used in Machine Learning. We have implemented a quantum feature map that can be trained, via optimization, to separate and embed classical data points, coming from two different classes, into a much larger Hilbert space. Quantum Mechanics suggests that the natural representation of a quantum bit is the Bloch sphere, therefore the embedding we want to train will be composed of a sequence of rotations on noncommuting axes to be applied to an input qubit. The training and the parameters of the embedding are flexible and can be manipulated in order to account for the specific needs of the different experimental platforms.
The atomic platform in which we realize the embedding is a Bose-Einstein Condensate (BEC) of 87Rb realized with an Atom-chip. We illustrate how the performance of Quantum Embedding depend on the degree of control on the actual system, thus on the level of experimental imperfections specific to the solutions adopted.
The aim of our study is to prove that this kind of approach is robust to experimental errors and that can be applied in practice, hence supporting the promising idea of hybrid quantum technologies for future Quantum Machine Learning applications.

I. Gianani, et al.,
Experimental Quantum Embedding for Machine Learning
Adv. Quantum Technol. 5, 2100140 (2022)

The supersolid is a long-sought quantum phase of matter combining properties of superfluids and crystals, finally discovered in quantum gases of magnetic atoms. The experiments usually cross a quantum phase transition from a homogeneous superfluid to the density-modulated supersolid. But very little is known about this novel type of phase transition. Here, we find experimentally and theoretically that the superfluid-to-supersolid quantum phase transition resembles ordinary crystallization transitions but with important novelties due to the peculiar ways in which supersolids are different from superfluids and solids. We see evidence of two types of transitions, continuous and discontinuous, which can be linked to the second- and first-order phase transitions expected for 1D and 2D systems, respectively. Interestingly, we find that the dimensionality of a supersolid depends not only on the underlying lattice structure but also on the structure of the density background that provides phase coherence among lattice sites. Our analysis provides a general framework based on Landau theory—a general theory of phase transitions—which allows us to reconcile previous results in the field. The continuous transitions we find provide access to excitation-free supersolids, which can be employed to study fundamental phenomena such as superfluidity and entanglement in this new state of matter.

G. Biagioni, et al.
Dimensional Crossover in the Superfluid-Supersolid Quantum Phase Transition
Phys. Rev. X 12, 021019 (2022)

A scientific workshop to discuss the most recent advancements in the context of ultracold atom physics and related fields. Experimental and theoretical groups from Palaiseau (France) and Florence (Italy) research areas will present their activities and discuss collaborations in topics ranging from metrology and entanglement to quantum transport and simulation.

The scientific program and all the information for attendance can be found on the workshop website

Our preprint on ultracold collisions in 6Li-53Cr mixtures is now on the arXiv! We have performed extensive Feshbach spectroscopy of various spin combinations revealing more than 50 resonances between 0 and 1500 G. By means of a full coupled-channel model, we have unambiguously assigned a complete set of quantum numbers to each resonance and derived a thorough characterization of the scattering properties of our system. This has enabled us to identify several resonances suitable for future few-body and many-body studies of mass-imbalanced Fermi mixtures. What is more, our work paves the way to the production of a new class of ultracold molecules possessing both electric and magnetic dipole moments.

Stay tuned!

A. Ciamei et al.
Exploring ultracold collisions in 6Li-53Cr Fermi mixtures: Feshbach resonances and scattering properties of a novel alkali-transition metal system
arXiv:2203.12965 (2022)

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Seminars & Events

Palaiseau-Florence Workshop on Ultracold Atoms:
Experimental and theoretical groups from Palaiseau (France) and Florence (Italy) research areas will present their activities and discuss collaborations. More info at quantumgases.lens.unifi.it/paf
Seminar by Prof. Carlos Sa de Melo:
Ultra-cold Fermi Gases with Three and Four Internal States: The Evolution from BCS to BEC Superfluidity in Multiband Systems ,
h. 12.00 Querzoli room, LENS.
Seminar by Dr. Dimitrios Trypogeorgos:
Unconventional topology with a Rashba spin-orbit coupled quantum gas,
h. 14.30 Querzoli room, LENS.
Firenze-Trieste workshop:
Two days of talks and scientific discussions with the theory groups of ICTP and SISSA,
ICTP, Trieste.
Firenze-Trieste workshop:
Two days of talks and scientific discussions with the theory groups of ICTP and SISSA,
Aula Querzoli, LENS.
Quantumgases retreat:
A full-day group meeting to discuss the activity of the different labs,
h. 9.00 Villa il Gioiello, Arcetri.
Fermi Colloqium by Prof. Wolfgang Ketterle:
New forms of matter with ultracold atoms: superfluids, supersolids and more,
h. 11.30 Querzoli room, LENS.
Seminar by Prof. Arno Rauschenbeutel:
Chiral Quantum Optics,
h. 11.00 Querzoli room, LENS.
The LENS QuantumGases group is glad to welcome in Florence Prof. Randall Hulet from Rice University. Prof. Hulet will be our guest for one month until mid July.