March 2025 - ITP-quantumseminare

Thursday's QIT seminar
by Ladina Hausmann 24 Mar '25

24 Mar '25

Hi all, this week Moritz Bürgi will talk about “Reference Systems in Quantum Cryptography”, see below for the abstract. The talk will take place on Thursday at 11:00 in HIT E 41.1. Best, Ladina %%%%%% Title: The Role of Reference Systems in Quantum Cryptography Abstract: Quantum mechanics is conventionally formulated with respect to a classical frame of reference, meaning that states and measurements are defined relative to a physical system which is treated classically. The existence of such a classical reference frame is thus implicitly assumed whenever we put quantum mechanics to use, for instance in quantum key distribution (QKD). We make the reference systems involved explicit and include them in our mathematical description. However, any physical systems, including those used as a reference, are ultimately quantum mechanical, a feature which has been ignored in QKD security proofs. We ask whether this inclusion poses any risks for security established in security proofs in conventional QKD by considering a simple prepare and measure protocol. In such a protocol we focus on the reference frame alignment phase of the parties involved and the subsequent state preparation phase. Based on a set of assumptions we motivate, we show that an eavesdropper can only establish correlations with the prepared states through the reference systems. We argue that security is not immediately compromised in the state preparation phase by explicitly considering the reference systems.

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Thursday's QIT seminar in HIT F13
by Ladina Hausmann 18 Mar '25

18 Mar '25

Hi all, This Thursday at 11:00 in HIT F13, Axel Pappalardo will tell us about "Energy consumption of a cat-qubit quantum memory”, see below for the abstract. Best, Ladina *** Title: Energy consumption of a cat-qubit quantum memory Abstract: The scalability of quantum computers is an important question for the achievability of a useful quantum computers, and the minimization of the energy consumption of the entire stack is a crucial part of this scalability. This work aims at optimizing this cost for a cat-qubit quantum memory, which utilizes the tunable noise bias of cat-qubits which grants an exponential suppression of bit-flip errors with the average photon number and allow one to construct a quantum memory by correcting only phase errors with a simple repetition code. Using the MNR methodology, we breakdown each operation of the repetition code and study their energetic cost, which allows us to optimize the energetic cost for the full stack of a quantum memory, and show that using a cat-qubit architecture, a round of repetition code with a logical error rate of $3.6\times10^{-6}$ could be performed using about $5.0 \si{\mJ}$.

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Review Notification center
by lists.phys.ethz.ch 11 Mar '25

11 Mar '25

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No seminar this week
by Ladina Hausmann 11 Mar '25

11 Mar '25

Hi all, there is no seminar planned for this week. Best, Ladina

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This week's QIT seminars
by Ladina Hausmann 04 Mar '25

04 Mar '25

Hi all, This week, we have two talks by our two visitors: - Philipp Höhn will talk on Tuesday at 14:45 in HIT J52 about “A correspondence between quantum error correcting codes and quantum reference frames”. - Rotem Arnon Friedman will talk on Thursday at 11:00 in HCI F 8 about “Computational quantum information theory -- an invitation for new inspiration” See below for the abstracts. Best, Ladina ****** Title: A correspondence between quantum error correcting codes and quantum reference frames Abstract: Redundancy is the hallmark of both quantum error correction and gauge theories. In this talk, I will show that this analogy is not merely a coincidence but that there is a deeper underlying structural relationship. The key ingredient to this observation is quantum reference frames (QRFs), which constitute a universal tool for dealing with symmetries in quantum systems. They define a split between redundant and physical information in gauge systems, thereby establishing a notion of encoding in that context. This leads to an exact dictionary between (group-based) quantum error correcting codes and QRF setups. In stabilizer codes, this uncovers a correspondence between errors and QRFs: every maximal set of correctable errors generates a unique QRF, and each QRF is associated with a unique class of correctable errors. This allows for a reinterpretation of the Knill-Laflamme condition and novel insights into the relation between correctability and redundancy. The dictionary also reveals a novel error duality, based on Pontryagin duality, and somewhat akin to electromagnetic duality. Time permitting, I will illustrate these findings in surface codes, which can be understood as both codes and lattice gauge theories. These findings may find use in code design and quantum simulations of gauge theories. [Based on https://arxiv.org/abs/2412.15317] **** Title: Computational quantum information theory -- an invitation for new inspiration Abstract: In this very informal seminar I would like to share with you -- the best QIT group in the world -- why we should be interested and carve new research paths in QIT, which take aspects of computational complexity into account. I will present two different works of mine: "Computational Entanglement Theory" (https://arxiv.org/abs/2310.02783, with Zvika Brakerski & Thomas Vidick) and "Computational Quantum Unpredictability Entropy" (soon on the arXiv, with Noam Avidan). I will focus on the many open questions that arise and share my enthusiasm with you!

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