IQIM Postdoctoral and Graduate Student Seminar

Abstract: Quantum systems exhibit complex dynamics marked by information scrambling, leading to phenomena such as long-range entanglement and thermalization. Local measurements can significantly alter these dynamics, which can freeze local degrees of freedom and give rise to new non-equilibrium phases and associated Measurement-induced Phase Transitions (MiPTs). Unlike the stochastic nature of monitored quantum trajectories, post-selected detector readouts yield deterministic dynamics governed by a non-Hermitian Hamiltonian, with MiPTs exhibiting distinct universal characteristics.

In this presentation, I will begin by revisiting the foundational principles of quantum measurements. I will then contrast the quantum dynamics of individual post-selected trajectories with their collective statistical behavior, using a solvable single-qubit model as a case study. Moving on to many-body systems, I will introduce a novel partially post-selected stochastic Schrödinger equation that captures a specific subset of quantum trajectories. This formalism will be applied to a model of Gaussian Majorana fermions. Employing a two-replica strategy and renormalization group (RG) techniques, I will demonstrate the robustness of the non-Hermitian MiPT's universality in the presence of limited stochasticity. Additionally, I will reveal that the transition to monitored universality occurs at a finite partial post-selection. This approach paves the way for utilizing non-Hermitian dynamics to investigate the characteristics of monitored quantum systems and tackle the challenges associated with post-selection