On an irregular basis various Special Seminars take place at the MPQ. The seminars are organized by scientists of our divisions, administration or staff representatives. The location will be announced with the event.
Room: Herbert Walther Lecture Hall Location: Max Planck Institute of Quantum Optics
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. [more]
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. [more]

From classical to quantum nature of high harmonic generation (Prof. Hamed Merdji)

I will review my recent progresses in high harmonic generation in semiconductors, stepping from its classical nature to the recent evidence of its non-classical properties. [more]
The pseudogap is mysterious metallic state of electrons which appears above the critical temperature of correlated electron superconductors, most prominently in the lightly-hole-doped cuprates. I argue that the pseudogap is best understood as the finite temperature realization of a metallic ground state with a spin liquid character, andpresent a theory using a bi-layer of ancilla qubits. This theory leads to a variational wavefunction for the pseudogap state, to gauge theories for transitions and crossovers out of the pseudogap, and to a unifying perspective on the cuprate phase diagram. [more]

"Charge migration and charge transfer in molecules initiated by attosecond pulses” (Prof. Mauro Nisoli)

The investigation of ultrafast processes initiated in molecules by light absorption is of crucial importance in various research areas, from molecular physics to material science, from chemistry to biology. They are at the heart of emerging technological applications, where photo-induced electron transfer and charge transfer play a key role. In the last few years, the use of attosecond pulses has demonstrated to be a very powerful tool for the investigation of physical processes evolving in molecules on time scales ranging from a few femtoseconds down to tens of attoseconds. The introduction of new attosecond spectroscopic techniques, together with the development of sophisticated theoretical methods for the interpretation of the experimental outcomes, allowed unravelling and investigating physical processes never observed before. The application of attosecond methods to molecular physics has opened new research frontiers. Experimental advances, in terms of new sources, devices and techniques, are still required, together with new theoretical tools and approaches, but attosecond molecular physics has firmly established as a mature research field. [more]
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