09:30 to 10:30 
David Weld (KITPUCSB, USA) 
Cold atoms, quantum simulation, and driven quasicrystals (Part II) (Online talk) Ultracold neutral atoms in modulated optical lattices are a flexible testbed for the experimental study of quantum matter driven far from equilibrium. I will first present a pedagogical introduction to this field of research from an unusual point of view, then describe results from a sequence of recent experiments in this area, on the physics of localization in driven quasicrystals. Time permitting, in this second part of the twopart talk I will also discuss a new tweezerbased degenerate gas platform under construction at UC Santa Barbara which aims at the study of quantum interactive dynamics.



11:30 to 12:10 
Jedediah Pixley (Rutgers University, USA) 
Infinite randomness and quasiperiodic fixed points at measurement induced phase transitions We will discuss the universal nature of measurement induced phase transitions (MIPTs) in random quantum circuits when the measurement profile follows a static profile. First, the measurement induced transition is shown to be unstable to static but spatially random perturbations and the transition flows off to an infinite randomness fixed point. Second, the nature of several distinct quasiperiodic profiles will be studied and nonPisot structures will be used to tune between irrelevant and relevant perturbations at the MIPT. In the latter case, the transition flows to an infinite quasiperiodic fixed point where the entanglement scaling is dictated by the wandering exponent of the quasiperiodic profile. The nature of these transitions are computed using large scale Clifford simulations and will be shown to be well described by real space renormalization group calculations.



12:10 to 12:50 
Sumilan Banerjee (IISc, India) 
Classical limit of a measurementinduced transition Chaotictononchaotic transitions play a prominent role in our understanding of the dynamical phase diagram of both quantum and classical systems. In quantum manybody systems, a certain kind of chaoticnonchaotic transitions, dubbed ‘measurementinduced phase transitions’ (MIPT), have led to a new paradigm for dynamical phase transitions in recent years. On the other hand, prominent examples of transition in chaos in classical dynamical systems are the stochastic synchronization transitions (ST). In this case, classical trajectories starting from different initial conditions synchronize when subjected to sufficiently strong common random stochastic noise. In this talk, I will establish a direct link between MIPT and ST by considering models of interacting quantum particles, whose positions are measured continuously, albeit weakly. In the semiclassical limit, the dynamics of the system is described by a stochastic Langevin equation where the noise and the dissipation terms are both controlled by the small quantum parameter and measurement strength. I will show the existence of a chaotictononchaotic transition in the Langevin evolution as a function of either interaction or noise/dissipation strength.



14:30 to 15:10 
Justin H. Wilson (Louisiana State University, USA) 
Measurement and feedbackdriven entanglement transition in the probabilistic control of chaos In this talk, I show how a dynamical entanglement transition in a monitored quantum system is revealed by a local order parameter with the addition of feedback. Classically, chaotic systems can be stochastically controlled onto unstable periodic orbits and exhibit controlled and uncontrolled phases as a function of the rate at which the control is applied. We show that such control transitions persist in open quantum systems where control is implemented with local measurements and unitary feedback. Starting from a simple classical model with a known control transition, we define a quantum model that exhibits a diffusive transition between a chaotic volumelaw entangled phase and a disentangled controlled phase. Unlike other entanglement transitions in monitored quantum circuits, this transition can also be probed by correlation functions without resolving individual quantum trajectories. Building on this, we define a version of this model with classically simulable stabilizer circuits and show that not only does the entanglement transition separate from the control transition, but it returns to the universality class found for the 1+1D entanglement transition in hybrid stabilizer circuits.



15:10 to 15:50 
Arnab Sen (IACS, India) 
Quantum scars in pure lattice gauge theories The Eigenstate Thermalization Hypothesis (ETH) shapes our understanding of thermalization in closed quantum manybody systems. In this talk, we outline the occurrence of quantum manybody scars (highenergy eigenstates that violate the ETH) in lattice gauge theories without dynamical matter due to the phenomenon of orderbydisorder in the Hilbert space. For some physically relevant models like the quantum link and the quantum dimer models, the existence of such anomalous states can be shown analytically for certain lattice geometries.



16:50 to 17:30 
Diptiman Sen (IISc, India) 
Effects of open ends on OTOCs and emergence of local conservation laws in periodically driven systems in one dimension In this talk we will consider two classes of periodically driven systems in one dimension. In the first case, we consider a spin1/2 $XY$ model in a transverse field, where the field is driven periodically in time. The periodic driving can generate two kinds of modes, topological modes (for which the phases of the Floquet eigenvalues are 0 or $\pi$) and nontopological modes (for which the phases can be arbitrary), which are localized at the ends of a finitesized system. We study the outoftimeordered correlators (OTOCs) of spin operators which are local ($\sigma^z$) or nonlocal ($\sigma^x$) in terms of JordanWigner fermions. The OTOCs of nonlocal operators show pronounced scrambling and unscrambling of quantum information after reflections from the ends of the systems. Further, the OTOCs of both local and nonlocal operators can detect the presence of end modes which give rise to oscillations as a function of the stroboscopic time. Both kinds of OTOCs show that information propagates with a maximum velocity known as the LiebRobinson bound.
In the second case, we study a system of fermions where there is an onsite potential which varies periodically in space, and the strength of the potential is varied periodically in time. We find that system becomes dynamically localized for special values of the driving strength and frequency. The dynamical localization gives rise to an extreme limit of the SuSchriefferHeeger model in which the nearestneighbor hoppings are zero and nonzero alternately; as a result, there are an extensive number of conserved quantities. Further, if there are densitydensity interactions between particles on nearestneighbor sites, the system effectively turns into the transverse field Ising model. We study the halfchain entanglement entropy versus the Floquet quasienergy and find that the large number of conserved quantities can give rise to a highly fragmented structure of the entanglement versus quasienergy plot. A study of the time evolution of the Loschmidt echo and some twopoint correlation functions show longtime oscillations indicating that the system has anomalous thermalization behavior.
References: S. Sur and DS, arXiv:2210.15302, S. Aditya and DS, arXiv:2305.06056.


