The recently proposed exact quantum solution for two δ-function-interacting particles with a mass-ratio 3:1 in a hard-wall box [Y. Liu, F. Qi, Y. Zhang and S. Chen, iScience 22, 181 (2019)] seemingly violates Gaudin's necessary condition for the Bethe Ansatz integrability of a system of semitransparent δ-function mirrors. This condition requires that if two mirrors cross at a dihedral angle...
Atomtronics is the emerging quantum technology of matter-wave circuits which coherently guide propagating ultra-cold atoms. The field benefits from the remarkable progress recently achieved in micro optics, allowing to control the coherent matter with enhanced flexibility on the micro-meter spatial scale. This way, both fundamental studies in quantum science and technological applications can...
We experimentally study the paradigmatic many-body problem of mobile impurities interacting with a homogeneous Bose-Einstein condensate (BEC). We use a combination of injection spectroscopy and many-body interferometry to access the injection spectrum (frequency domain) and the impurity-coherence function (time domain). Our experiments start with a spin-polarized BEC confined in an optical box...
Recent experimental advances of quantum simulators allow unprecedented microscopic studies of the structure of strongly correlated quantum matter. In the Fermi-Hubbard model, believed to underly high-Tc superconductivity and accessible to ultracold atom experiments in optical lattices, this allows to study the origins of unconventional pairing from a new perspective — a long-awaited goal of...
The Fermi-Hubbard model is an iconic model of solid state physics that is believed to capture the intricate physics of strongly correlated phases of matter, including high-Tc superconductivity. Such a state of matter is supposedly achieved upon doping a cold antiferromagnetic Mott insulator, and magnetically mediated charge ordering in the form of pairing of dopants (holes), in particular, is...
We developed a new advanced ultra-cold Dysprosium (Dy) apparatus, which incorporates a quantum gas microscope (QGM) with a resolution of a quarter micrometer. The QGM and the cooling
and trapping regions are within the same vacuum glass vessel assuring simple atom transport between them. We demonstrate the essential experimental steps of laser and evaporative cooling,
lattice loading,...
Discrete time crystals created in a Bose-Einstein condensate of ultracold atoms bouncing on an oscillating mirror [1] can exhibit dramatic breaking of time-translation symmetry [2, 3], allowing the creation of discrete time crystals having tens of temporal lattice sites and suitable for hosting a broad range of condensed matter phenomena in the time dimension [4].
We will discuss temporal...
Adiabatic protocols are employed across a variety of quantum technologies, from implementing state preparation and individual operations that are building blocks of larger devices, to higher-level protocols in quantum annealing and adiabatic quantum computation. The problem of speeding up these processes has garnered a large amount of interest, resulting in a menagerie of approaches, most...
Floquet engineering is an important tool for realizing topologically nontrivial band structures for charge-neutral atoms in optical lattices. However, the preparation of a topological-band-insulator-type state of fermions, with one nontrivial quasi-energy band filled completely and the others empty, is challenging as a result of both driving induced heating as well as imperfect adiabatic state...
Quantum science promises great potential to revolutionize our current technologies. The past few years have witnessed a rapid progress on using arrays of individually trapped atoms as a programmable quantum processor. However, several predominant challenges remain, including reconfigurable individual addressability for qubit/spin operation and non-demolish selective detection, which lead to...
The relationship between many-body interactions and dimensionality is key to emergent quantum phenomena. A striking example is the Bose gas, which upon confinement to one dimension (1D) obeys an infinite set of conservation laws, prohibiting thermalization and steering dynamics. We experimentally demonstrate that the integrable dynamics of a Bose gas can persist deep within the dimensional...
Whether discussing interacting many-body physics with cold atoms, quantum metrology, or quantum computing, there are important questions around how large an entangled many-body state we can usefully and reliably prepare in analogue quantum simulators subject to decoherence. Given that information spreading and entanglement growth are limited by Lieb-Robinson bounds, the useful system size will...
We shall present our results for the fourth cluster coefficients of the homogeneous unitary spin 1/2 Fermi gas as functions of the internal-state mass ratio, over intervals constrained by the 3- or 4-body Efimov effect. For this we use the Endo-Castin 2016 conjecture (validated for equal masses by Hou and Drut in 2020) in a numerically efficient formulation making the sum over angular momentum...
Negative absolute temperature entails a situation where the entropy of a closed system reduces as the internal energy increases, and this leads to the peculiar situation that atoms in a band dominantly occupy the highest energy states in the band. Here we report the observation of negative absolute temperatures in a triangular optical lattice—a non-bipartite lattice where geometric...
We consider a quasi-one-dimensional dipolar condensate in a step-like analogue black hole setup. It is shown that the existence of roton excitations impacts significantly the Hawking radiation spectrum:
The emitted radiation depends on the depth of the roton minimum, and is in general more intense. In addition, we find a novel spontaneous particle creation mechanism with no counterpart in...
Crossing a continuous phase transition results in the formation of topological defects with a density predicted by the Kibble-Zurek mechanism (KZM). We report on two predictions beyond KZM:
First, it is shown that the statistics of defects follow a binomial distribution with N Bernoulli trials associated with the probability of forming a topological defect at the locations where multiple...
Dysprosium is a fascinating candidate for studying cooperative and collective effects in dense ultra-cold media. With the largest groundstate magnetic moment of all elements in the periodic table (10 Bohrmagnetons), it offers a platform to study the effect on scattering of light due to competition between magnetic dipole-dipole interactions (DDI) and light induced correlations. In a...
Very recent advances on dipoles in optical lattices and tweezer arrays are opening many intriguing novel possibilities, both for the simulation of Hubbard models and of spin models. I will first comment on extended Hubbard models, showing how strong inter-site interactions lead to a peculiar dynamics, characterized by Hilbert-space shattering and interaction-induced localization in absence of...
Motivated by a recent experiment on a square-lattice Rydberg atom array realizing a long-range dipolar XY model [Chen et al., Nature (2023)], we numerically study the model's equilibrium properties. We obtain the phase diagram, critical properties, entropies, variance of the magnetization, and site-resolved correlation functions. We consider both ferromagnetic and antiferromagnetic...
The effect of dipolar interactions on harmonically trapped BECs has been the subject of intense and fruitful research over recent years, but despite being theoretically calculated over 15 years ago [1] the modification of the BEC transition temperature due to dipole-dipole interactions has, up to now, not been experimentally observed. We will present our experimental findings on this topic;...
We report the experimental implementation of dynamical decoupling on a small, non-interacting ensemble of up to 25 optically trapped, neutral Cs atoms.
The qubit consists of the two magnetic-insensitive Cs clock states, which are coupled by microwave radiation.
We observe a significant enhancement of the coherence time when employing Carr-Purcell-Meiboom-Gill (CPMG) dynamical decoupling.
A...
One-dimensional gases offer a convenient and flexible platform for investigating open problems in modern physics, such as the full understanding of strongly interacting, out-of-equilibrium quantum systems. In particular, this work focuses on strongly repulsive one-dimensional gases consisting of two equally balanced spin components under a box confinement. To induce nonequilibrium dynamics,...
We consider the far-from-equilibrium quantum transport dynamics in a 1D Josephson junction chain of multi-mode Bose-Einstein condensates. We develop a theoretical model to examine the experiment of R. Labouvie et al. [Phys. Rev. Lett. 115, 050601 (2015)], wherein the phenomenon of negative differential conductivity (NDC) was reported in the refilling dynamics of an initially depleted...
Due to anisotropic long-range interactions, degenerate ultra-cold dipolar gases of Erbium and Dysprosium exhibit supersolidity, an exotic phase of matter both density-modulated and phase coherent. It is theorized that these supersolids maintain their phase coherence due to a superfluid background. While density modulation can be directly observed and phase coherence emerges from...
We report on recent breakthroughs in two experiments employing Feshbach-resonant mixtures of fermions.
In radio-frequency spectroscopic measurements on fermionic $^{40}$K (or bosonic $^{41}$K) atoms immersed as impurities in a Fermi sea of $^6$Li atoms, we observed mediated polaron-polaron interactions [1]. Our results confirm the prediction of Fermi-liquid theory that the sign of this...
The ground-state properties of two-component bosonic mixtures in a one-dimensional optical
lattice are studied both from few- and many-body perspectives. We rely directly on a microscopic Hamiltonian with attractive inter-component and repulsive intra-component interactions to
demonstrate the formation of a quantum liquid. We reveal that its formation and stability can be
interpreted in...
Gauge theories, a fundamental framework of modern physics, govern the intricate dynamics of elementary particles that constitute the world we know of. The decades-long quest to understand quantum systems operating under gauge symmetries presents both theoretical and experimental interests, with applications ranging from early-universe cosmology and heavy-ion collisions to condensed matter...
The realization of the Bose-Hubbard model with cold atoms, twenty years ago, can be considered the birth of quantum simulation. Today, advanced quantum simulators provide us with the opportunity to explore more exotic models, including models with flat energy bands, multi-band models, or models with long-range interactions. In these contexts, I discuss the intriguing scenario of Bose-Einstein...
Models of quantum many-body phases of matter may be realized using fermionic ultracold atoms in place of the electrons, and engineered optical potentials to emulate a crystal lattice. Quantum simulation of this kind takes advantage of the capability to adhere to a theoretical model, while the tunability of model parameters enables quantitative comparison with theory.
As an example,...
Quantum simulations with neutral atoms offer the unique opportunity to experimentally address outstanding problems in many-body quantum physics. I will report on recent results on the realization and microscopic study of a fractional quantum Hall state in an optical lattice. Our work provides a starting point for exploring other entangled topological matter with ultracold atoms.
Building...
Three atom types have been responsible for nearly all the remarkable progress in quantum degenerate gas experiments, namely alkalis, alkaline earths, and dipolar lanthanides. Meanwhile main-group elements III-VIII remain unexplored in the quantum degenerate regime.
Our work focuses on ultracold indium, which is a main-group III element. Indium is a multipurpose atom that contains many...
A quantum Hall system is characterized by non-trivial topological order of its underlying quantum states. While topological order cannot be accessed using local measurements, it leads to specific signatures in the structure of entanglement upon spatial partition, characterized by the entanglement spectrum. According to the Li-Haldane conjecture, the entanglement spectrum corresponds to a...
Resonantly interacting mixtures of ultracold fermionic atoms provide versatile and highly controllable platforms with which to explore a wealth of phenomena occurring in strongly-correlated systems: from helium liquids and solid-state materials, up to nuclear and quark matter. Here, I will discuss recent progress of my experimental team in making, probing and characterizing novel 6Li-53Cr...
Diffusion Monte Carlo calculations on the possibility of having self-bound one-dimen-sional droplets of SU(6) $\times$ SU(2) ultracold fermionic mixtures are presented. We found that, even though arrangements with attractive interactions with only two spin types are not self-bound, mixtures with at least three kinds of fermions form stable small drops. However, that stabilization...
Quantum fluctuations can stabilize bosonic mixtures and Bose-Einstein condensates with dipolar interactions against the collapse predicted by the mean-field theory. This stabilization mechanism allows for two new states of matter to arise: self-bound quantum droplets and dipolar supersolids. When dipolar interactions between the atoms are present, the droplets can self-assemble into arrays and...
We show that a Tonks-Girardeau gas that is immersed in a Bose-Einstein condensate can undergo a transition to a crystal-like Mott state with regular spacing between the atoms without any externally imposed lattice potential. We characterise this phase transition as a function of the interspecies interaction and temperature of the Tonks gas, and show how it can be measured via accessible...
The interest in developing solid theoretical frameworks to describe analog quantum simulation arises from the diverse range of potential applications it offers in areas such as condensed-matter physics, high-energy physics or quantum chemistry, in an era where fully fault-tolerant operations have not yet taken over NISQ (noisy,
intermediate scale, quantum) devices. One of my previous work has...
Generation, storage and utilization of correlated many-body quantum states are crucial objectives of future quantum technologies and metrology. Such states can be generated by the spin-squeezing protocols. In this work [1-2], we consider the dynamical generation of spin squeezing in a lattice system composed of ultra-cold fermionic atoms in the Mott phase at half-filling. To induce the...
We report on the first quantum simulation of the Hall effect for strongly interacting fermions [1]. By performing direct measurements of current and charge polarization in an ultracold-atom simulator, we trace the buildup of the Hall response in a synthetic ladder pierced by a magnetic flux, going beyond stationary Hall voltage measurements in solid-state systems. We witness the onset of a...
A cornerstone in the description of quantum fluids is the Bogoliubov theory used to explain the emergence of superfluidity in ensembles of weakly-interacting bosons. At the microscopic level, this theory predicts that interactions deplete the condensate through the formation of pairs of bosons with opposite momenta, known as quantum depletion. Exploiting the capability to detect individual...
I will discuss the results of a theoretical investigation into the supersolid state of a dipolar quantum Bose gas confined within an infinite tube potential [1-3]. This system serves as a thermodynamic idealization of cigar-shaped dipolar Bose gases, which have been utilized in recent experiments to prepare supersolids [4]. Our study presents phase diagrams as a function of the average linear...
I present our anomaly in the temperature dependence of the thermodynamics of a one-dimensional Bose gas. The anomaly exists for any contact repulsive interaction strength and is a reminiscence of a superfluid-normal phase transition. It signals unpopulated states below the hole branch in the excitation spectrum. The anomaly temperature is of the order of the hole-branch maximal energy. The...
Measuring the temperature of an interacting fermionic cloud of atoms in the BCS limit represents a delicate task. In the literature temperature measurements have so far been only suggested in an indirect way, where one sweeps isentropically from the BCS to the BEC limit. Instead we suggest here a direct thermometry, which relies on measuring the column density and comparing the obtained data...
Our project aims to experimentally demonstrate that weakly interacting Bose condensed atoms bouncing on a periodically driven atomic mirror can spontaneously break time-translational symmetry to form a discrete time crystal [1]. The resonantly tuned bouncing ensemble can evolve along long-lived stable orbits with a period multiple times larger than the driving period [2] thus creating a large...
Driven-dissipative systems are characterized by the appearance of steady-states. Upon parameter change, they can undergo dissipative phase transitions between different types of steady-states. One of the paradigmatic examples for a first order dissipative phase transition is the driven nonlinear single-mode optical resonator. The poster reports on the corresponding realization within an...
Quantum gas systems provide a unique experimental platform to study the crossover between Bose–Einstein condensed molecular pairs and Bardeen–Cooper–Schrieffer superfluidity. The few studies in optical lattices have so far focused on the case when only the lowest Bloch band is populated, thus excluding orbital degrees of freedom. Here we demonstrate the preparation of ultracold Feshbach...
Boyle's 1662 observation that the volume of a gas is, at constant temperature, inversely proportional to pressure, offered a prototypical example of how an equation of state (EoS) can succinctly capture key properties of a many-particle system. Such relations are now cornerstones of equilibrium thermodynamics. Extending thermodynamic concepts to far-from-equilibrium systems is of great...
The Hall effect, originating from the motion of charged particles in magnetic fields, has deep consequences for the description of materials, extending far beyond condensed matter where it was initially observed.
Understanding such an effect in interacting systems represents a formidable challenge, even for small magnetic fields.
Using an atomic quantum simulator where the motion of...
