Two electrons are better than one... In the Yb lab we produce Bose-Einstein condensates and degenerate Fermi gases of ytterbium atoms. These atoms offer metastable electronic states, ultranarrow clock transitions, multicomponent fermions with SU(N) interactions: a whole range of experimental tools that allow new possibilities for quantum simulation and quantum information processing.

We demonstrate a novel way of synthesizing spin-orbit interactions in ultracold quantum gases, based on a single-photon optical clock transition coupling two long-lived electronic states of two-electron 173Yb atoms. By mapping the electronic states onto effective sites along a synthetic “electronic” dimension, we have engineered fermionic ladders with synthetic magnetic flux in an experimental configuration that has allowed us to achieve uniform fluxes on a lattice with minimal requirements and unprecedented tunability. We have detected the spin-orbit coupling with fiber-link-enhanced clock spectroscopy and directly measured the emergence of chiral edge currents, probing them as a function of the flux. These results open new directions for the investigation of topological states of matter with ultracold atomic gases.

L. F. Livi et al.,
Synthetic Dimensions and Spin-Orbit Coupling with an Optical Clock Transition
Phys. Rev. Lett. 117, 220401 (2016)

Global Positioning System (GPS) dissemination of frequency standards is ubiquitous at present, providing the most widespread time and frequency reference for the majority of industrial and research applications worldwide. On the other hand, the ultimate limits of the GPS presently curb further advances in high-precision, scientific and industrial applications relying on this dissemination scheme. Here, we demonstrate that these limits can be reliably overcome even in laboratories without a local atomic clock by replacing the GPS with a 642-km-long optical fiber link to a remote primary caesium frequency standard. Through this configuration we stably address the 1S03P0 clock transition in an ultracold gas of 173Yb, with a precision that exceeds the possibilities of a GPS-based measurement, dismissing the need for a local clock infrastructure to perform beyond-GPS high-precision tasks. We also report an improvement of two orders of magnitude in the accuracy on the transition frequency reported in literature.

C. Clivati et al.,
Measuring absolute frequencies beyond the GPS limit via long-haul optical frequency dissemination
Opt. Express 24, 11865 (2016)

We report on the experimental observation of a strongly interacting gas of ultracold two-electron fermions with an orbital degree of freedom and magnetically tunable interactions. This realization has been enabled by the demonstration of a novel kind of Feshbach resonance occurring in the scattering of two 173Yb atoms in different nuclear and electronic states. The strongly interacting regime at resonance is evidenced by the observation of anisotropic hydrodynamic expansion of the two-orbital Fermi gas. These results pave the way towards the realization of new quantum states of matter with strongly correlated fermions with an orbital degree of freedom.

G. Pagano et al.,
Strongly Interacting Gas of Two-Electron Fermions at an Orbital Feshbach Resonance
Phys. Rev. Lett. 115, 265301 (2015)

See also the Physics Viewpoint by S. Cornish:

S. Cornish
Controlling Collisions in a Two-Electron Atomic Gas
Physics 8, 125 (2015)

Chiral edge states are a hallmark of quantum Hall physics. In electronic systems, they appear as a macroscopic consequence of the cyclotron orbits induced by a magnetic field, which are naturally truncated at the physical boundary of the sample. Here we report on the experimental realization of chiral edge states in a ribbon geometry with an ultracold gas of neutral fermions subjected to an artificial gauge field. By imaging individual sites along a synthetic dimension, we detect the existence of the edge states, investigate the onset of chirality as a function of the bulk-edge coupling, and observe the edge-cyclotron orbits induced during a quench dynamics. The realization of fermionic chiral edge states is a fundamental achievement, which opens the door towards experiments including edge state interferometry and the study of non-Abelian anyons in atomic systems.

M. Mancini et al.,
Observation of chiral edge states with neutral fermions in synthetic Hall ribbons
Science 349, 1510 (2015)

See also the Science Perspective by A. Celi and L. Tarruell:

A. Celi and L. Tarruell
Probing the edge with cold atoms
Science 349, 1450 (2015)

We report on the first direct observation of fast spin-exchange coherent oscillations between di fferent long-lived electronic orbitals of ultracold 173Yb fermions. We measure, in a model-independent way, the strength of the exchange interaction driving this coherent process. This observation allows us to retrieve important information on the inter-orbital collisional properties of 173Yb atoms and paves the way to novel quantum simulations of paradigmatic models of two-orbital quantum magnetism.

G. Cappellini et al.,
Direct Observation of Coherent Interorbital Spin-Exchange Dynamics
Phys. Rev. Lett. 113, 120402 (2014)

See also the Physics Viewpoint by A. M. Rey:

A. M. Rey
Observing the Great Spin and Orbital Swap
Physics 7, 95 (2014)

Correlations in systems with spin degree of freedom are at the heart of fundamental phenomena, ranging from magnetism to superconductivity. The effects of correlations depend strongly on dimensionality, a striking example being one-dimensional (1D) electronic systems, extensively studied theoretically over the past fifty years. However, the experimental investigation of the role of spin multiplicity in 1D fermions — and especially for more than two spin components — is still lacking. Here we report on the realization of 1D, strongly correlated liquids of ultracold fermions interacting repulsively within SU(N) symmetry, with a tunable number N of spin components. We observe that static and dynamic properties of the system deviate from those of ideal fermions and, for N > 2, from those of a spin-1/2 Luttinger liquid. In the large-N limit, the system exhibits properties of a bosonic spinless liquid. Our results provide a testing ground for many-body theories and may lead to the observation of fundamental 1D effects.

G. Pagano et al.,
A One-Dimensional Liquid of Fermions with Tunable Spin
Nature Phys. 10, 198 (2014)

Yb people

Lorenzo Franchi
PhD student
Lorenzo Livi
PhD student
Giacomo Cappellini
Postdoc
Jacopo Catani
Scientific staff
Massimo Inguscio
Scientific staff
Leonardo Fallani
Scientific staff
Former members:
Marcel Diem
Giovanni Giusfredi
Jonathan T. Green
Pietro Lombardi
Marco Mancini
Pablo Cancio Pastor
Guido Pagano
Florian Schäfer
Carlo Sias

Yb contacts

For further information, request of material, job opportunities, please contact:

Leonardo Fallani
(fallani@lens.unifi.it)

Yb funding

ERC CoG TOPSIM
PRIN2012 AQUASIM
EU FP7 SIQS
INFN FISh