Cs Quantum Gas Microscope

A quantum gas microscope for strongly interacting topological phases.

We have built a new Quantum Gas Microscope experiment with bosonic Caesium atoms. What is unique about our experiment is the tunability of interactions, a 2D superlattice potential and large homogeneous systems of >3000 atoms prepared in a repulsive box potential. We are broadly interested in studying complex quantum many-body systems in and out-of-equilibrium. More recently, we have started to combine our experimental setup with additional control capabilities towards hybrid digital-analog quantum simulation. Below we highlight some of our recent projects!

We are currently looking for PhD and Master students!!

Towards computational quantum simulation

We explore the intersection of quantum information science and analog quantum simulation - an exciting frontier for studying complex quantum many-body systems, both in and out of equilibrium. By integrating digital control elements into our analog quantum simulator, we are developing new experimental techniques that allow us to probe novel observables and prepare advanced initial states beyond simple product states in the occupation basis.

original

Subsystem return probabilities:
The probability for a quantum many-body system to return to its initial state after dynamical evolution encodes rich information about the system’s underlying physics, with connections to quantum chaos, many-body dynamics, and high-energy physics. However, this global return probability is typically exponentially suppressed with system size, making it extremely challenging to measure experimentally.

Illustration of the initial state |ψ0〉 and time-evolved state |ψ(t)〉. The SRP measures the probability of finding the initial state bitstring of length N in the time-evolved state snapshots.

To overcome this, we introduce the subsystem return probability - a quasi-local observable that captures key features of the global return probability while remaining experimentally accessible. Using quantum gas microscopy, we study its dynamics across both short and long timescales. In the short-time regime, we observe a dynamical quantum phase transition driven by genuine higher-order correlations. At long times, the subsystem return probability provides a direct quantitative measure of the effective dimension and structure of the accessible Hilbert space in the thermodynamic limit, which we demonstrate for fragmented Hamiltonians that emerge in the presence of kinetic constraints. Our results establish the subsystem return probability as a powerful new probe of non-equilibrium quantum dynamics and equilibrium properties alike - highlighting how quantum simulators can access complex physics beyond conventional measurements of local densities in a model-agnostic way.

Recent preprint: S. Karch et al. arXiv:2501.16995

 

Arbitrary nearest-neighbor orbital operators: 
We have developed a novel technique for state preparation and readout based on optical superlattice potentials, enabling local manipulations at the level of individual bonds within an optical lattice.

Schematic drawing of the projection of the many-body wave function onto isolated double wells using a superlattice potential and the corresponding representation of the double-well manipulations on a Bloch sphere.

Quantum gas microscopes have transformed quantum simulations with ultracold atoms by providing access to single-site resolved images of quantum many-body systems. However, most measurements so far have been limited to the occupation basis. In our recent work, we demonstrate how kinetic operators - such as kinetic energy and current operators - can be measured and controlled with single-bond resolution. Beyond simple expectation values, our single-shot measurements provide access to full counting statistics and higher-order correlation functions. Furthermore, site-resolved programmable potentials enable spatially selective, parallel readout in different bases, as well as the engineering of arbitrary initial states.

Original publication: A. Impertro et al. Phys. Rev. Lett. 133, 063401 (2024)
Viewpoint in Physics highlighting our article: Visualizing Atom Currents in Optical Lattices

Quantum simulation of topological many-body phases

Neutral atoms in optical lattices offer exceptional opportunities for exploring complex quantum many-body systems, both in and out of equilibrium, within a highly controlled environment. A natural class of models readily accessible in these systems are Hubbard models, where particle dynamics are governed by the interplay between tunneling and on-site interactions. This facilitates fundamental investigations of the nature of the phase diagram of paradigmatic models such as the Fermi-Hubbard model. In contrast, quantum simulation of strongly correlated topological phases of matter requires the development of novel engineering techniques, as the relevant microscopic interactions do not naturally arise in these systems.

a Schematic of the flux ladder; b Phase diagram

In this context, Floquet engineering—also known as periodic driving—has emerged as a powerful method. Over the past decade, it has been successfully employed to realize a variety of lattice models with topological band structures, and numerous experimental techniques have been developed to probe their geometric properties. However, with few exceptions involving interacting two-particle systems, experiments have been carried out almost exclusively in the non-interacting regime. While these studies clearly demonstrate the potential of Floquet engineering, extending it to many-particle strongly-interacting systems remains a significant challenge. The main challenge in this regard is heating due to the periodic drive, which eventually results in an infinite-temperature state.

In a recent study, were able to leverage the new capabilities of our cesium quantum gas microscope in order to realize a large Floquet-engineered many-body flux ladder with about 24 hard-core bosons at half filling in a low-entropy state, whose temperature we benchmarked to be on the order of the tunnel coupling. By tuning the coupling ratio K/J we explore the phase diagram which exhibits a transition from a Meissner to a vortex regime. These results represent a significant advance in Floquet many-body physics and marks an exciting first step toward realizing large fractional Chern insulators with cold atoms, opening the door to studying topological order and exotic anyonic excitations with microscopic resolution and control [A. Impertro et al., Nature Physics 21, 895 (2025)].

PhD theses from our team:

List of publications

List of publications

Here you can find a list of previous and recent experimental results from our Cs team. more
Numerical & theoretical work

Numerical & theoretical work

Here we collect research from our group that we performed together with our theory colleagues in order to develop a better understanding of the quantum many-body systems we are planning to study. more

Team members:

Alex, Monika, Julian, Immanuel, SeungJung and Simon (from left to right)
  • SeungJung Huh, PostDoc
  • Simon Karch, PhD
  • Irene Prieto Rodriguez, PhD
  • Juan-Yi Pon, student assistant

 

 

 

 

 

 

Former members

Web-View
Print Page
Open in new window
Estimated DIN-A4 page-width
Go to Editor View