Category: Seminars

Our visiting researcher Maksym Teslyk is presenting work which is part of his Ph.D. dissertation. It relates to both classical and quantum physical information theory and to general relativity. The picture is Kip Thorne’s black hole visualization from the movie Interstellar.

Abstract:

A spherical system of mass M is represented as a set of Unruh horizons. The approach allows to estimate the total entropy of Unruh radiation from the set and calculate its ratio to the Bekenstein-Hawking entropy. The contribution of mass and spin s of the emitted particles is taken into account. For large values of M, the ratio exhibits susceptibility to the intrinsic degrees of freedom and varies from 0% (s = 0) to 19% (s = 5/2).

Time and place: Thursday Nov. 16th, room PS439 in Pilestredet 35.

Tuesday Nov. 17th we have the pleasure of hearing Noah Oldfield, from Simula Research Lab, presenting results and research question related to his ongoing project. It involves software testing on actual quantum computers. See the abstract below for more details.

Quantum program outputs enable the development of unique quality assurance techniques. Our research focuses on efficiently distinguishing a specialized ideal state vector from the sampled state vector of a program using inference techniques.

To accomplish this, we utilized a hill climbing algorithm for stochastic searches between basis transformations, circumventing the exponential scaling of brute force searches with increased qubit numbers. We conducted tests on a suite of automatically generated faulty programs.

For those programs with state vectors representable in the Hadamard basis, we observed improved testing runtimes and enhanced phase gate fault detection.

Sobolev space formulation of density-functional theory: Solving the v-representability problem.

14th September 13:00, room PS340, building P35.

Density-functional theory is one of the principal methods in physics, chemistry and materials science used for calculating properties of many-body systems based on their electronic structure. It rests on a reformulation of the explicit energy expression in terms of the full quantum state into an implicit energy functional defined for a reduced
quantity, the one-particle density. While considerably reducing the computational complexity, if corresponding approximations are available, this reformulation introduces certain mathematical problems. Most notably, it is not explicitly known which set of densities actually stems from solutions to the quantum many-body problem, i.e., the lowest-eigenvalue solution to the time-independent Schrödinger equation. In this talk a recently found resolution to this so-called “v-representability problem” is presented in the reduced setting of a 1-dim ring system with densities from a Sobolev space.

Monday May 19th we had the pleasure of having Justin Wells visiting our hub. He gave a very interesting presentation on his work within experimental condensed matter physics. It spent quite widely – ranging from implementing qubits in silicon to magnetic properties – and how they are related to ducklings. Despite this rather wide scope, those of us who attended go to hear a presentation which was both accessible and even entertaining.

If you want to learn more about Justin’s research activities, you can read more here:

Ny professor med kvantematerialer som spesiale

https://sites.google.com/site/quantumwells/home

Friday June 9th 2023 we had the pleasure of listening to Tanner Culpitt, postdoc at the Hylleraas Centre, giving a presentation entitled Electronic Structure and Molecular Dynamics in a Strong Magnetic Field. In addition to outlining how such systems can be studied non-perturbatively, he also shared ideas on how quantum computers may be useful in this context.

The seminar was part of a double MatMod seminar, in which also George Hitching from the Faculty of Education and International Studies at OsloMet presented a talk on Moduli of bundles over algebraic curves.

Full abstract for Tanners presentation:

The electronic structure and dynamics of molecules in magnetic fields have historically been treated perturbatively. A perturbative treatment is successful at weaker field strengths, such as those found on Earth. At higher field strengths such as those found in white dwarf stars or neutron stars, a perturbative treatment is inadequate, and new tools are needed to accurately model electronic structure and dynamics. This talk will focus on the theoretical development and application of these tools. Additionally, recent developments in the application of quantum algorithms for the calculation of molecular properties in a magnetic field will be discussed.

Friday 26^th of May Kishore Thapliyal, from Palacky University, Olomouc, Czecch Republic, will visit the Quantum Hub and tell us about his work on secure quantum computation.

Title and abstract:

Experimental generation of engineered multi-mode quantum states to use in secure quantum computation 

The idea of secure multiparty computation will be briefly reviewed. With the help of an example relevance of a quantum solution for such secure computation tasks in socioeconomic problems will be mentioned. Such relevant socioeconomic problems could be auction, voting, private comparison, etc. Quantum solutions for one such problem, anonymous veto, will be proposed with focus on the requirements of the desirable protocol. The solution uses multiparty densecoding which requires entanglement to be shared among the voters. A multiparty densecoding based protocol for quantum conference will also be discussed. Generation, transmission, and maintenance of such entangled states is a challenging task. In this context, some non-Gaussian operations are known useful for entanglement distillation. Here, we discuss photon subtraction on both signal and idler beams of a multi-mode twin beam generated experimentally. Joint photon-number distributions of photon-subtracted twin beams are monitored by an iCCD camera. The effect of photon subtraction on average photon numbers, nonclassical and non-Gaussian properties and entanglement of the generated states is studied considering the states obtained by subtracting up to four signal and idler photocounts.  

References 

[1] S. Mishra, K. Thapliyal, A. Parakh, and A. Pathak, Quantum anonymous veto: A set of new protocols, EPJ Quantum Technology 9, 14 (2022).  

[2] K. Thapliyal, J. Peřina Jr., V. Michalek, R. Machulka, and O. Haderka, Experimental characterization of photon-subtracted twin beams, Communicated (2023). 

It was our pleasure to invite you all to an interesting seminar by Simen Kvaal from University of Oslo. Simen is a quantum physicist with the Hylleraas centre at the Department of Chemistry, UiO. The title of his talk is “No need for a grid: Gaussians for the time-dependent Schrödinger equation”.

Read more about it here: https://arxiv.org/abs/2207.00271