Seminars

Host: Molecular Physics

Quantum control of ultracold ion-atom collisions

Hybrid systems of laser-cooled trapped ions and ultracold atoms combined in a single experimental setup have recently emerged as a new platform for fundamental research in quantum physics and chemistry [1]. Reaching the ultracold s-wave quantum regime has been one of the most critical challenges in this field for a long time. Unfortunately, the lowest attainable temperatures in experiments using the Paul ion trap are limited by the possible rf-field-induced heating related to the micromotion. [more]

Controlling the uncontrollable: Quantum control of open systems

Quantum control addresses the issue of driving a system to a desired objective. Manipulation of quantum systems is achieved by coherent control which relies on constructive and destructive interference of the quantum amplitudes, i.e., quantum coherence. The key ingredient, coherence, is extremely sensitive to any external perturbation. In reality all quantum systems are open, thus, are subject to environmental effects. The interaction with the environment degrades the required agent, coherence, leading to a detrimental effect on coherent control. Quantum control of an open system is therefore a challenge. For this study we employ a thermodynamically consistent master equation. In this framework, the open system dynamics depend on the control protocol due to the dressing of the system by the drive. This interrelation serves as the key element for control. The influence of the external drive is incorporated within the dynamical equation, enabling an indirect control of the dissipation. The control paradigm is displayed by analyzing entropy changing state to state transformations, heating and cooling N-levels systems, accelerating the approach to equilibrium. Following, we study the generation of quantum non-unitary maps via coherent control. These include both reset maps with complete memory loss. The other extreme where the control is optimized to minimize the dissipation is demonstrated by a single and two qubit unitary maps. [more]

Quantum sensor networks as exotic field telescopes for multi-messenger astronomy

Multi-messenger astronomy, the coordinated observation of different classes of signals originating from the same astrophysical event, provides a wealth of information about astrophysical processes with far-reaching implications. [more]
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