General seminar by Cosimo Rusconi (Columbia University)

General seminar given by Cosimo Rusconi (Columbia University), on Thursday 20 March 2025 at 11:00am in the Auditorium of the Institut d'Optique Graduate School in Palaiseau, on the topic: "Universal scaling laws for correlated decays of many body quantum systems".

Abstract: "Increasing the density of quantum devices opens avenues to explore novel regimes of many-body quantum dynamics and enhance the performance of various quantum applications such as precise sensing. At the same time, this effort poses new challenges as densely packed systems exhibit correlated dissipation, significantly impacting the decay rate of correlated quantum states. It is thus natural to ask: What is the maximum decay rate of a system with correlated dissipation? Addressing this question for large numbers of particles is however complicated by the exponential scaling of the Hilbert space dimension. In this talk, I will present an alternative method that circumvents this difficulty. We reformulate the problem of maximal decay rate into finding the ground state energy of a 2-local Hamiltonian. Leveraging ideas for approximating the ground state of Hamiltonian systems, we provide rigorous analytical bounds for the maximal decay rate of generic many-body quantum systems. Our bounds are universal in that they only depend on global properties of the decoherence matrix (which describes dissipative couplings between atoms) and agnostic of the specific microscopic interactions. For many classes of physically-relevant systems, the bounds are tight, resulting in scaling laws with system size. As a particular application, I will discuss Superradiance in extended lattices of atoms — a well-known open problem in quantum optics. I will demonstrate how our general method allows us to derive rigorous scalings for the radiation burst. I will conclude by illustrating the role that the scaling laws play in complex quantum optics phenomena such as driven dissipative phase transition beyond the usual cavity scenario. In particular, i will address the problem of collective resonance fluorescence and superradiant lasing transition in free space that have attracted significant attention in recent years."