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.

Observation of chiral edge states with neutral fermions in synthetic Hall ribbons

Physicists have used cold atomic gases to simulate quantum phenomena that we normally associate with much more complex systems, such as solid-state materials. Because the properties of these gases are so tunable, it is also possible to create conditions that otherwise do not exist in nature. Zhang et al. studied an exotic type of magnetism in an array of pancake-shaped atomic clouds of 87Sr. They prepared the atoms' nuclei in different combinations of 10 quantum states. They then shone pulses of light at the atoms to deduce the properties of the atoms' interactions. The interactions were independent of the atoms' nuclear states—a hallmark of an unusual symmetry that theorists predict may lead to interesting collective effects.

Science , this issue p. [1467][1]

 [1]: /lookup/doi/10.1126/science.1254978

/pdf/spectroscopic-observation-of-su-n-symmetric-interactions-in-ef2a3mm5bu.pdf

Spectroscopic observation of SU(N)-symmetric interactions in Sr orbital magnetism

Using the two stable electronic states of alkaline-earth atoms, an orbital spin-exchange interaction—the building block of orbital quantum magnetism—has been observed in a fermionic quantum gas.

/pdf/observation-of-two-orbital-spin-exchange-interactions-with-1jd1jp8gj0.pdf

Observation of two-orbital spin-exchange interactions with ultracold SU(N)-symmetric fermions

The emergence of a special type of fluidlike behavior at large scales in one-dimensional (1D) quantum integrable systems, theoretically predicted in O. A. Castro-Alvaredo et al., Emergent Hydrodynamics in Integrable Quantum Systems Out of Equilibrium, Phys. Rev. X 6, 041065 (2016)10.1103/PhysRevX.6.041065 and B. Bertini et al., Transport in Out-of-Equilibrium XXZ Chains: Exact Profiles of Charges and Currents, Phys. Rev. Lett. 117, 207201 (2016)10.1103/PhysRevLett.117.207201, is established experimentally, by monitoring the time evolution of the in situ density profile of a single 1D cloud of ^{87}Rb atoms trapped on an atom chip after a quench of the longitudinal trapping potential. The theory can be viewed as a dynamical extension of the thermodynamics of Yang and Yang, and applies to the whole range of repulsive interaction strength and temperature of the gas. The measurements, performed on weakly interacting atomic clouds that lie at the crossover between the quasicondensate and the ideal Bose gas regimes, are in very good agreement with the theory. This contrasts with the previously existing "conventional" hydrodynamic approach-that relies on the assumption of local thermal equilibrium-which is unable to reproduce the experimental data.

/pdf/generalized-hydrodynamics-on-an-atom-chip-7fyxba2sea.pdf

Generalized Hydrodynamics on an Atom Chip

The many-body problem is ubiquitous in the theoretical description of physical phenomena, ranging from the behaviour of elementary particles to the physics of electrons in solids. Most of our understanding of many-body systems comes from analysing the symmetric properties of Hamiltonian and states: the most striking examples are gauge theories such as quantum electrodynamics, where a local symmetry strongly constrains the microscopic dynamics. The physics of such gauge theories is relevant for the understanding of a diverse set of systems, including frustrated quantum magnets and the collective dynamics of elementary particles within the standard model. In the last few years, several approaches have been put forward to tackle the complex dynamics of gauge theories using quantum information concepts. In particular, quantum simulation platforms have been put forward for the realisation of synthetic gauge theories, and novel classical simulation algorithms based on quantum information concepts have been form...

Lattice gauge theory simulations in the quantum information era

The physics of one-dimensional many-body systems is rich but still insufficiently understood. An ultracold atom experiment investigates the behaviour of one-dimensional strongly correlated fermions with a tunable number of spin components.

/pdf/a-one-dimensional-liquid-of-fermions-with-tunable-spin-5cjzmj9824.pdf

A one-dimensional liquid of Fermions with tunable spin

Atomic memories for flying photonic qubits are an essential ingredient for many applications like e.g. quantum repeaters. Verification of the coherent transfer of information from a light field to an atomic superposition is usually obtained using an optical read-out. In this paper we report the direct detection of the atomic coherence by means of atom interferometry. We experimentally verified both that a bichromatic laser field closing a Raman transition imprints a distinct, controllable phase on the atomic coherence and that it can be recovered after a variable time delay.

Reading the phase of a Raman excitation with a multi-state atomic interferometer

We introduce a multi-state interferometer on an atom chip with an enhanced resolution and nearly perfect fringe visibility. We demonstrate its application as a sensor of the state-dependent interaction of atoms with circularly polarized light.

/pdf/a-multi-state-interferometer-on-an-atom-chip-1382nap2nf.pdf

A multi-state interferometer on an atom chip

We introduce a new experimental apparatus for cold atom based on an atom chip setup. It is going to
feature for the first time the ability to interchange the atom chip frequently and rapidly. The setup will be paired with
photonic structures on-chip for the detailed study of matter-light interactions. Here, we present the design of the new
apparatus and present first ideas on how to use the unique combination of cold-atom technology with interchangeable
photonics components, both, for basic research and applications to modern information technologies.

/pdf/nanometric-surface-probing-through-ultra-cold-atoms-dqy3xao9h9.pdf

Florian Schaefer

Papers

A one-dimensional liquid of Fermions with tunable spin

Reading the phase of a Raman excitation with a multi-state atomic interferometer

A multi-state interferometer on an atom chip

Nanometric surface probing through ultra-cold atoms