Hi all,
This week we will have two seminars:
(1) On Tuesday, our visitor Riccardo Castellano will talk about “The entropic coherence is a necessary resource for non-energy preserving gates”. The talk will take place on Tuesday at 12:30 in HIT E41.1.
(2) On Thursday, our other visitor Wolfgang Wieland will talk about ”Luminosity Bound of Gravitational Waves by Non-Perturbative Quantum Effects of Gravity”. The talk will take place at 11:00 in HIT E41.1.
See below for the abstracts.
Best,
Ladina
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Title:
The entropic coherence is a necessary resource for non-energy preserving gates
Abstract:
Under the energy conservation law, we consider the task of implementing non-energy preserving gates (NEPG) on a finite-dimensional system S via an interaction with an external battery B providing or absorbing the required energy. We prove that the entropic coherence (closely related to the relative entropy of coherence) is a resource for this task, and find a lower bound on its minimum amount that has to be present in the battery to be able to implement NEPG with fixed precision. Assuming that the dimensionality of the battery scales polynomially with the precision, we strengthen the latter bound by a factor of 2. An immediate corollary is that any finite-dimensional battery can not exceed a certain minimal error in the gate implementation task. Moreover, under assumptions on the density of energy levels in the battery Hamiltonian, our main results imply additional lower bounds on the minimal amount of energy and quantum Fisher information required to implement the gate. We show that these bounds can be stronger than the universal bounds previously established in the literature.
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Title:
Luminosity Bound of Gravitational Waves by Non-Perturbative Quantum Effects of Gravity
Abstract:
This talk presents recent progress on a non-perturbative quantisation of gravitational subsystems on a light cone. Starting from the covariant phase space for the γ-Palatini--Holst action, we identify an auxiliary conformal field theory (CFT), which carries a representation of the constraint algebra of general relativity on a null surface. In the model, the radiative data, which is encoded into the shear of each null generator, is mapped into an auxiliary current algebra on each light ray. We study the resulting quantum theory for both bosonic and fermionic representations. In the fermionic representation, the central charge on each null ray is positive, for bosons it is negative. To avoid non-unitary representations, the central charge must be positive. I explain how this requirement alters the spectrum of the radiated power. In this way, we obtain a bound on the radiated power (Bondi flux) of gravitational waves in asymptotically flat spacetimes. The talk is based in part on arXiv:2402.12578, arXiv:2401.17491, arXiv:2104.05803, arXiv:2504.10802.