## Research Groups

#### Quantum Optics and Spectroscopy

The research group led by Rainer Blatt investigates quantum processes in a system of few ions held in ion traps. The experiments aim at achieving complete control over all quantum degrees of freedom in... Read more …

#### Dipolar Quantum Gases

The research team led by Francesca Ferlaino focuses on the study of dipolar quantum phenomena, using strongly magnetic atomic species. In 2012, the group has created the first Bose-Einstein... Read more …

#### Ultracold Atoms and Quantum Gases

The research group led by R. GRIMM investigates ultracold particle systems consisting of optically trapped quantum gases at temperatures close to absolute zero. Because of their superb experimental... Read more …

#### Superconducting quantum circuits

Gerhard Kirchmair’s research group works on superconducting circuits and their application for quantum computation and simulation. Superconducting Josephson junctions are used to realize the quantum... Read more …

#### Many-Body Quantum Optics

The research group led by Hannes Pichler studies quantum optical systems, quantum many-body physics and quantum information. The group aims at laying the theoretical foundations for next generation... Read more …

#### Quantum Optics

Wittgenstein awardee Peter Zoller’s research group studies topics in the fields of theoretical quantum optics and atomic physics as well as quantum information and condensed matter theory. The... Read more …

## Most Recent Preprints

Demonstration of two-dimensional connectivity for a scalable error-corrected ion-trap quantum processor architecture
arXiv:2406.02406
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A major hurdle for building a large-scale quantum computer is to scale up the number of qubits while maintaining connectivity between them. In trapped-ion devices, this connectivity can be provided by physically moving subregisters consisting of a few ions across the processor. The topology of the connectivity is given by the layout of the ion trap where one-dimensional and two-dimensional arrangements are possible. Here, we focus on an architecture based on a rectangular two-dimensional lattice, where each lattice site contains a subregister with a linear string of ions. We refer to this architecture as the Quantum Spring Array (QSA). Subregisters placed in neighboring lattice sites can be coupled by bringing the respective ion strings close to each other while avoiding merging them into a single trapping potential. Control of the separation of subregisters along one axis of the lattice, known as the axial direction, uses quasi-static voltages, while the second axis, the radial, requires control of radio frequency signals. In this work, we investigate key elements of the 2D lattice quantum computation architecture along both axes: We show that the coupling rate between neighboring lattice sites increases with the number of ions per site and the motion of the coupled system can be resilient to noise. The coherence of the coupling is assessed, and an entangled state of qubits in separate trapping regions along the radial axis is demonstrated. Moreover, we demonstrate control over radio frequency signals to adjust radial separation between strings, and thus tune their coupling rate. We further map the 2D lattice architecture to code primitives for fault-tolerant quantum error correction, providing a step towards a quantum processor architecture that is optimized for large-scale fault-tolerant operation.

Exploring the interplay between mass-energy equivalence, interactions and entanglement in an optical lattice clock
arXiv:2406.03804v1
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We propose protocols that probe manifestations of the mass-energy equivalence in an optical lattice clock (OLC) interrogated with spin coherent and entangled quantum states. To tune and uniquely distinguish the mass-energy equivalence effects (gravitational redshift and second order Doppler shift) in such setting, we devise a dressing protocol using an additional nuclear spin state. We then analyze the interplay between photon-mediated interactions and gravitational redshift and show that such interplay can lead to entanglement generation and frequency synchronization. In the regime where all atomic spins synchronize, we show the synchronization time depends on the initial entanglement of the state and can be used as a proxy of its metrological gain compared to a classical state. Our work opens new possibilities for exploring the effects of general relativity on quantum coherence and entanglement in OLC experiments.

Hamilton-Jacobi-Bellman equations for Rydberg-blockade processes
arXiv:2402.12956
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More Preprints
We discuss time-optimal control problems for two setups involving globally driven Rydberg atoms in the blockade limit by deriving the associated Hamilton-Jacobi-Bellman equations. From these equations, we extract the globally optimal trajectories and the corresponding controls for several target processes of the atomic system, using a generalized method of characteristics. We apply this method to retrieve known results for CZ and C-phase gates, and to find new optimal pulses for all elementary processes involved in the universal quantum computation scheme introduced in [Physical Review Letters 131, 170601 (2023)].

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