Seminare

Narrow resonances corresponding to quantum transitions in atoms, molecules, quantum dots, rare-earth ions and color centers constitute the basis of quantum optics with numerous applications in sensing, imaging, computation, communication, etc. The highest quality atomic resonances have been achieved in atomic clocks. Their realization requires low atomic density, vacuum environment, laser cooling below 100 nK temperature, and magnetic traps or optical lattices. [mehr]

The electric dipole moment of polar molecules and their rich internal structure makes them excellent candidates for applications in precision measurements, controlled ultracold chemistry, and quantum simulations. Many applications require that the molecular sample is cooled to limit the number of occupied quantum states and trapped. [mehr]

Abstract. We discuss the question of how can one treat the laser-induced (or laser-assisted)high-order processes of electrons (bound or free) nonperturbatively, in such a way that boththe electron-atom interaction and the quantized nature of radiation be simultaneously takeninto account? An analytic method is proposed to answer this question in the generalframework of nonrelativistic quantum electrodynamics. As an application, a quantum opticalgeneralization of the strong-field Kramers-Heisenberg formula has been derived fordescribing high-harmonic generation (HHG). [mehr]

The field of quantum computation heavily relies on the belief that quantum computation violates the extended Church Turing thesis, namely, that quantum many-body systems cannot be simulated by classical ones with only polynomial overhead. Importantly, we must ask: what experimental evidence do we have for this bold assumption? A major effort towards providing such evidence had concentrated on random quantum circuit sampling (RCS) as in the famous supremacy experiment by Google from 2019. I will describe a recent work with Gao, Landau, Liu and Vazirani in which we give a polynomial time classical algorithm for simulating such RCS experiments. Our algorithm gives strong evidence that RCS cannot be the basis for near term experimental evidence for scalable exponential quantum advantage. [mehr]

Development of quantum hardware and software is progressing rapidly. With the availability of first generally-accessible quantum computers, their potential use for applications can increasingly be explored. One prospective field of application is data science in the medical sector, which faces challenges difficult to address with currently available methods. An example is medical imaging, where frequently only limited training data is available – making the use of classical AI methods difficult. However, presently available quantum computers are still limited in the number of qubits, the connectivity and are affected by noise. [mehr]