Hi all,

Next week we have two seminars:

(1) On Tuesday, Luca Ciceri will talk about “Quantum Reference Frames Perspectives on Holographic Codes”. The talk will take place in HIT E41.1 at 11:15 (2) On Thursday, Andrea Smirne will talk about “When is a non-Markovian quantum process classical? Multi-time non-classicality and quantum combs”. The talk will take place in HIT J51 at 14:00.

See below for the abstracts.

Best, Ladina %%%%%%%%

Title: Quantum Reference Frames Perspectives on Holographic Codes

Abstract: Holography, quantum reference frames and quantum error correction are three distinct yet connected research areas in physics. A dictionary between stabiliser quantum codes and ideal quantum reference frames has been recently formalised. In this work we apply it to holographic codes. We challenge their interpretation as discrete toy models of a quantum gravity theory by looking for analogies between the quantum reference frames emerging from the code structure and boundary dressings. This approach is also beneficial to a deeper understanding of boundary quantum reference frames in holography, since this is not well appreciated in the literature. To achieve this, we leverage the quantum LEGO formalism. This allows us to describe the structure of holographic codes by focusing on how individual tensors are contracted. By providing the interpretation of contraction as a quantum reduction map we connect this formalism to gauge theories, understanding contractions as partial gauge fixings. Using the inverse reduction map we also complete the quantum LEGO formalism by describing how tensors are cut. Thanks to this result, we pave the way for the analysis of how ideal quantum reference frames transform when tensors are glued together. Our preliminary work in this direction shows that it is always possible to find a quantum reference frame for the contracted tensors, provided knowledge of the reference frames before contraction. These results provide a solid base to advance the analysis of quantum reference frames in holographic codes and their comparison with boundary dressings, as well as understanding the relation with their continuum counterparts.

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Title: When is a non-Markovian quantum process classical? Multi-time non-classicality and quantum combs

Abstract: In this talk, I will address the question of which properties and phenomena are genuinely quantum, in the context of temporal quantum processes that are sequentially probed by measurements over time. After briefly revisiting the general framework for defining multi-time correlators in open quantum systems and introducing the Kolmogorov consistency conditions that distinguish classical from quantum multi-time statistics, I will focus on recent results that provide a complete characterization of classical temporal processes—those that can, in principle, be simulated using only classical resources. Building on this characterization, it is shown that for non-Markovian processes (i.e., processes with memory) the absence of quantum coherence does not necessarily imply classical behavior. Relying on a general tool to deal with multi-time processes in the quantum setting, namely quantum combs, I will then present a direct link between classicality and the vanishing of system-environment quantum discord, highlighting how memory effects fundamentally alter the boundary between classical and quantum dynamics. Finally, I will demonstrate that, unlike in the memoryless case, certain non-Markovian processes are intrinsically quantum, displaying nonclassical statistics that are independent of the specific measurement scheme used to probe them.