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## Quantum technologies meet quantum impurity physics

#### Location: CECAM-ISR

#### Organisers

Technologies for directly manipulating quantum properties of matter at the most fundamental level—that of individual quantum bits or qubits—hold great promise for humanity [1,2]. They not only embody flexible experimental platforms for exploring quantum physics, but also enable new paradigms in computer science for efficiently solving otherwise intractable problems. Recently, several such technologies have reached a sufficient level of maturity and applicability to attract wide interest, both by governments and multinational companies, and the field has since advanced by leaps and bounds, leading to the so-called “second quantum revolution”.

A primary goal of most quantum technologies is to isolate several (or many) qubits (be they superconducting, based on semiconductor quantum dots or dopants, or realized by ultracold atoms or ions) from their environment as much as possible, while still allowing them to be manipulated. Yet, coupling to the environment is eventually unavoidable, not only because of practical limitations on the fabrication and control of such systems, but also since desired coupling between sets of qubits, and even the manipulation of individual qubits in the context of performing a quantum computation, is most often achieved by way of an environment acting as a “quantum bus” [3].

The physics of small, strongly-interacting quantum fluctuating systems (qubits) coupled to large environments has held a central role in condensed matter and chemical physics for more than half a century. Theoretical descriptions of such systems are traditionally referred to as “quantum impurity models”. Impurity physics may feature many exotic phenomena, including quantum phase transitions and non-Fermi-liquid physics. Notwithstanding, it has applications in many fields ranging from nonequilibrium transport through quantum dots to solvation dynamics. Several exciting research paths presently make this connection between quantum technologies and quantum impurity physics even stronger. This includes the use of quantum impurities for the realization of a new robust quantum computing platform based on non-abelian anyons [4].

Advances in quantum technology can help us in deepening our understanding of quantum impurities. Here the idea is to employ “quantum simulators”, quantum systems which can be tailor-designed to follow a strongly-correlated model, to simulate phenomena beyond the reach of classical computers. Recent progress in the fabrication, control, and measurement of complex superconducting circuits opens the door towards their use as quantum impurity simulators. In particular, these simulators enable the study of quantum impurities from a new experimental angle, relying not on electrical transport measurements but on microwave excitation and probing at the level of single quanta — photons [5].

Making further advances in the study of quantum impurities thus requires the combined efforts of theoreticians with diverse analytical and numerical tools, together with experimentalists specializing in the different physical platforms mentioned above. The purpose of the planned workshop is to bring together leading experts on the various directions mentioned above, so as to allow them to learn and discuss each other’s work and form new collaborations. Our groups have played a leading role in much of the aforementioned theoretical progress, thus it is natural for us to organize and host it.

## References

**Israel**

Guy Cohen (Tel Aviv University) - Organiser

Moshe Goldstein (Tel Aviv University) - Organiser

Eran Sela (Tel Aviv University) - Organiser