Strongly-correlated Rydberg quantum gases

Ultracold atomic gases are ideally suited for exploring the quantum physics of many-body systems and for investigating quantum matter and exotic quantum phenomena. We make use of the extraordinary properties of highly-excited Rydberg atoms in dense atomic gases to explore the realm of strongly-correlated many-body physics.

Far from equilibrium dynamics of a Rydberg spin system

The dynamics of strongly-interacting quantum systems constitutes one of the most challenging problems in modern science, touching basic concepts of statistical physics, thermodynamics and quantum physics. These systems are particularly intriguing since disorder gives rise to a variety of collective phenomena like anomalously slow dynamics, the breakdown of thermalization and the emergence of novel glassy phases of matter. As a model system we use a frozen gas of Rydberg atoms where the spin is encoded in two electronically excited states. This system is ideally suited for exploring the dynamics of isolated quantum systems due to the huge dipolar interaction between Rydberg atoms. Using coherent laser beams and arbitrary pulse sequences of microwave radiation, we experimentally implement novel tools for quantum engineering and diagnostics.

Transport of Rydberg excitations

We study the transport of Rydberg excitations in a cold atomic cloud. A single excitation to an impurity Rydberg state couples via resonant dipole-dipole interactions to the background atoms, which are dressed with another Rydberg state via electromagnetically induced transparency. The transparent background is therefore rendered absorptive around the impurity. This allows direct optical detection of transport dynamics. The imaging process presents a tunable degree of decoherence, which enables the study of different transport regimes.

Nonlinear photon interactions in a Rydberg-EIT medium

Making photons interact lies at the heart of modern quantum optics and has applications for example in all-optical quantum information processing. Coupling light to an interacting gas of Rydberg atoms under conditions of electromagnetically induced transparency (EIT) provides a strong optical nonlinearity, which allows for photonic interactions on the single photon level. This rapidly evolving field of Rydberg-EIT paves the way for applications such as photon transistors and fosters investigations of many-body physics with interacting photons as well as exotic states of light.
Our group recently predicted a two-body, two-photon resonance that enhances the optical nonlinearity in the regime of low optical depth per blockade radius and allows to alter the absorptive and dispersive properties of the Rydberg gas.

Engineering Rydberg-spin hamiltonians

Rydberg atoms constitute an ideal platform to perform quantum simulations of Heisenberg-spin systems. By mapping the spin degree of freedom to two atomic states, involving at least one high-lying Rydberg state, Ising-, XX- and XXZ-models can be realized. Depending on the specific form of the underlying Hamiltonian, interesting phases of matter can be observed that are yet not fully understood.
However, Rydberg quantum simulators (as well as simulators on other platforms) are usually only suited to study a specific class of Hamiltonians and it is often quite demanding or even impossible to change the implemented Hamiltonian in a controlled way.
One approach to overcome this fundamental limitation is to engineer terms in a given interaction Hamiltonian by means of global control pulses. Traditionally, these techniques have been developed in nuclear magnetic resonance (NMR) in order to filter interactions and single particle dephasing. Nowadays, the use of pulse sequences have been extended to not only cancel terms, but to modify them in a desired way. Our goal is to study relaxation dynamics in a disordered spin system under general XYZ- Hamiltonians using microwave pulse sequences.

The Rydberg team

Carlos Brandl Sebastian Geier David Grimshandl Renato Ferracini Alves Titus Franz André Salzinger Annika Tebben Dr. Gerhard Zürn Prof. Matthias Weidemüller ... and you?

Publications by the Rydberg project