Joint ICTP/SISSA Condensed Matter Seminar, 6 June at 11:00, Christopher W. Wächtler

[CMSP Seminars Secretariat]

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  Joint ICTP/SISSA Condensed Matter Seminar
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** * * Tuesday**, 6 June 2023, 11:00*****(CET)** * **
In person: *Luigi Stasi Seminar Room **(Leonardo Building, second floor)***
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/Zoom: 
https://zoom.us/meeting/register/tJwrdeytqTojGNLqCNDrn-f6tsSuW1j-1Bbq/<https://zoom.us/meeting/register/tJIsfuuhqjsrE9EZY2loNxNobg8Lf39NUVHJ>

Speaker: *Christopher W. Wächtler *(UC Berkeley)

Title: *Topological synchronization of classical and quantum systems

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Abstract:

For many quantum mechanical applications dissipation is often regarded 
as an undesirable yet unavoidable consequence because it potentially 
degrades quantum coherences and renders the system classical. However, 
interactions with the environment can also be considered a fundamental 
resource for striking collective effects typically impossible in 
Hamiltonian systems. A hallmark of such collective behavior in 
nonequilibrium systems is the phenomenon of synchronization: in the 
complete absence of any time-dependent forcing from the outside, a group 
of oscillators adjusts their frequencies such that they spontaneously 
oscillate in unison. With the recent developments in quantum technology 
which allow one to exquisitely tailor both the system and environmental 
properties, synchronization has emerged in the quantum domain with 
various different examples ranging from nonlinear oscillators to spin-1 
systems, superconducting qubits and optomechanics. However, to observe 
synchronization in large networks of classical or quantum systems 
demands both excellent control of the interactions between nodes and 
accurate preparation of the initial conditions due to the involved 
nonlinearities and dissipation. This limits its applicability for future 
devices. In this talk, I will present a potential route towards 
significantly enhancing the robustness of synchronized behavior in open 
nonlinear systems that utilizes the power of topological insulators, 
which exhibit an insulating bulk but conducting surface states, known as 
topological edge states. These edge states display a surprising immunity 
to a wide range of local deformations and even circumvent localization 
in the presence of disorder. By combining nontrivial topological 
lattices with nonlinear oscillators, we show that synchronized motion 
emerges at the lattice boundaries in the classical (mean field) as well 
as the quantum regime. Furthermore, the synchronized edge modes inherit 
the topological protection known from closed systems with remarkably 
robust dynamics against local disorder and even random initial 
conditions. Our work demonstrates a general advantage of topological 
lattices in the design of potential experiments and devices as 
fabrication errors and longterm degradation are circumvented in this 
way. This is especially important in networks where specific nodes need 
special protection.