January 2024 - ITP-quantumseminare

No group seminar this week
by Ladina Hausmann 29 Jan '24

29 Jan '24

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

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Tomorrow's QIT Seminar at 14:00pm in HIT E 41.1
by Ladina Hausmann 22 Jan '24

22 Jan '24

Hi all, Tomorrow our visitor Shunji Tsuchiya will tell us about "Evolution of entanglement entropy in strongly correlated bosons in an optical lattice". See below for the abstract. The talk will take place at 2pm in HIT E 41.1 Best, Ladina *** Title: Evolution of entanglement entropy in strongly correlated bosons in an optical lattice Abstract: We investigate the time evolution of the second-order Rényi entropy (RE) for bosons in a one-dimensional optical lattice following a sudden quench of the hopping amplitude [1]. Specifically, we examine systems that are quenched into the strongly correlated Mott-insulating (MI) regime from the MI limit. In this regime, the low-energy excited states can be effectively described by fermionic quasiparticles known as doublons and holons. They are excited in entangled pairs through the quench dynamics. By developing an effective theory, we derive a relation between the RE and correlation functions associated with doublons and holons. This relation allows us to analytically calculate the RE and obtain a physical picture for the RE in terms of doublon holon pairs. We show that the RE is proportional to the population of doublon-holon pairs that span the boundary of the subsystem. Our quasiparticle picture introduces some remarkable features that are absent in previous studies on the dynamics of entanglement entropy in free-fermion models. It provides with valuable insights into the dynamics of entanglement entropy in strongly-correlated systems. [1] Phys. Rev. Research 5, 043102 (2023)

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Tomorrow's QIT Seminar at 14:00pm in HIT E 41.1
by Ladina Hausmann 15 Jan '24

15 Jan '24

Hi all, Tomorrow Caroline Tornow will tell us about her thesis "Error-mitigated circuit knitting with classical communication". See below for the abstract. The talk will take place at 2pm in HIT E 41.1 Best, Ladina *** Title: Error-mitigated circuit knitting with classical communication Abstract: Large-scale fault-tolerant quantum computers are still out of reach. Furthermore, it is a key challenge to develop error mitigation methods for noisy quantum devices and run applications on the limited number of qubits. Circuit knitting allows the simulation of a quantum computer with more qubits than are physically available, however, at the expense of a simulation overhead. Here, a large quantum circuit is partitioned into multiple fragments that fit on devices with fewer qubits. In this work, we study a variant of this technique, called circuit knitting with classical communication [1] which employs classical communication between the circuit fragments. Naturally, circuit knitting with classical communication requires measurements which are carried out mid-circuit and, based on their outcomes, trigger quantum operations. Due to inevitable qubit idling times, these dynamic quantum circuits are currently more prone to noise than quantum circuits consisting only of unitary gates. The dominant noise sources are dephasing and quantum crosstalk. In this talk, we introduce circuit knitting with classical communication and its implementation on a noisy quantum computer. We present two techniques to suppress and mitigate noise, dynamical decoupling and zero-noise extrapolation, and show how they can be tailored to dynamic quantum circuits. Using these techniques, we demonstrate error-mitigated circuit knitting with classical communication for graph-state circuits. Our results indicate that error suppression and mitigation make quantum applications involving dynamic quantum circuits, such as circuit knitting, feasible on currently available noisy quantum computers. [1] C. Piveteau and D. Sutter, “Circuit knitting with classical communication”, IEEE Transactions on Information Theory (2023)

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Todays QIT Seminar at 2pm in HIT E41.1
by Ladina Hausmann 09 Jan '24

09 Jan '24

Hi all, I hope you had a good start in the new year! We are starting again this week with a talk from our guest Vojtěch Havlíček on “On Quantum Statistical Query Learning”. See below for the abstract. The talk will take place at 14:00 in HIT E41.1. Best, Ladina %%%%% Title: On Quantum Statistical Query Learning Joint work with Louis Schatzki (UIUC) and Srinivasan Arunachalam (IBM Almaden). Abstract: Statistical Query Learning (SQ) is a restriction of PAC learning in which learners form hypotheses by querying expectation values over the data distribution and labels. It is well known that SQ cannot learn the concept class of parities, even under uniform distribution. This shows that it is a restriction of PAC.   We study an obvious quantum generalization of SQ, proposed by Arunachalam, Grilo and Yuen, which is not separable from a quantum generalization of PAC by parity learning and our main result is a task that separates the two learning classes. To prove it, we built on Feldman‘s work on statistical query dimension, which yields lower bounds on SQ learning. I will discuss our result, the lower bounding technique and some of its applications.

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