From superradiant criticality to solidification

2019. 05. 17. 10:15
Building F, Entrance III, seminar room of Department of Theoretical Physics
András Vukics (Wigner RCP)

Title: "From superradiant criticality to solidification - fundamental limitation of ultrastrong coupling between light and atoms"


Download the abstract: pdf.

Fermionic Quantum Computation

2019. 05. 20. 14:15
Building F, Entrance III, seminar room of Department of Theoretical Physics
János Asbóth (Wigner RCP)

Speaker: Janos Asboth (Wigner RCP)

Topic: “Fermionic Quantum Computing” (informal journal-club talk and discussion)

Time: May 20, 14:15
Location: seminar room of the theory department (to be confirmed)
Janos will introduce the concept through a classic paper and a recent PRL:
Fermionic quantum computation
Sergey Bravyi, Alexei Kitaev
Majorana-Based Fermionic Quantum Computation
T. E. O’Brien, P. Rożek, and A. R. Akhmerov
This event is initiated by the BME Nanoelectronics group and jointly organized by the Nanoelectronics group and the Exotic Quantum Phases group.

PhD Progress Reports

2019. 06. 03. 09:00
2nd- and 3rd-year PhD students

2nd year students


9.00-9.10 Tosson Elalaily
9.10-9.20 Lévay Sára
9.20-9.30 Németh Károly
9.30-9.40 Balassa Gábor
9.40-9.50 Nagy Dániel Bálint


9.50-10.20 Break


3rd year students


10.20-10.30 Kovács-Krausz Zoltán
10.30-10.40 Sánta Botond
10.40-10.50 Farkas Dániel
10.50-11.00 Pető János


11.00-11.20 Break


11.20-11.30 Gresits Iván
11.30-11.40 Csóré András
11.40-11.50 Boros Csanád Örs
11.50-12.00 Németh Gergely

12.00-    Evaluation by the Doctoral School board members

Ergodicity-breaking from Hilbert space fragmentation

2019. 06. 03. 14:15
Building F, Entrance III, seminar room of Department of Theoretical Physics
Tibor Rakovszky (TU Munich)

Event of the Exotic Quantum Phases Seminar Series:


Title: Ergodicity-breaking from Hilbert space fragmentation in dipole-conserving Hamiltonians


Abstract: "We show that the conservation of charge and dipole moment - characteristic of fracton systems - leads to an extensive fragmentation of the Hilbert space, which in turn can lead to a breakdown of thermalization. As a concrete example, we investigate the out-of-equilibrium dynamics of one-dimensional spin-1 models that conserve charge (total spin z component) and its associated dipole moment. First, we consider a minimal model with only three-site terms and find that the infinite temperature auto-correlation saturates to a finite value, thus showcasing non-ergodic behavior. This absence of thermalization is identified as a consequence of the strong fragmentation of the Hilbert space into exponentially many invariant subspaces in the local  basis, arising from the interplay of dipole conservation and local interactions. Second, we extend the model by including longer-range terms and find that they lead to a weak fragmentation: the system still has exponentially many invariant subspaces, but they are no longer sufficient to avoid thermalization for typical initial states. Nevertheless, as long as the Hamiltonian has finite range, there are exponentially many states that do not thermalize, some of which we construct explicitly. Based on: P Sala, TR, R Verresen, M Knap, F Pollmann:"

Interface symmetry and non-helical states in topological insulator-based heterostructures

2019. 06. 17. 14:00
Building F, Entrance III, seminar room of Department of Theoretical Physics
Ilya Vekhter (LSU)

Incorporating topological insulators (TIs) into prototype devices requires creating interfaces between topological and non-topological materials. It is often assumes that the interface states have the same properties as the well-studied helical Dirac states at the surfaces of TIs. I consider a planar boundary between a topologically-trivial semiconductor and a TI, and show that the topological interface states may be qualitatively different from those at the vacuum surface, are controlled by the residual symmetry of the interface,  and may exhibit elliptical contours of constant energy and complex spin textures with broken helicity. I will also discuss experimental signatures of broken symmetry of these states and propose measurements for its detection.

PhD Progress Reports

2019. 07. 01. 09:00
1st-year PhD students

9.00-9.10 Sulyok Ábel
9.10-9.20 Okvátovity Zoltán
9.20-9.30 Soleimani Saeedeh
9.30-9.40 Zsebéné Zsuga Lilla
9.40-9.50 Kollarics Sándor


9.50-10.10 Break


10.10-10.20 Hódsági Kristóf
10.30-10.40 Erdős Boglárka
10.40-10.50 Olasz Soma
10.50-11.00 Mezei Gréta
11.00-11.10 Nyáry Anna


11.10-11.20 Break


11.20-11.30 Csősz Gábor
11.30-11.40 Orosz Gergely Imre
11.40-11.50 Nyitrai Gábor
11.50-12.00 Preissinger, Katharina
12.00-12.10 Nyári Bendegúz


12.10-13.00 Evaluation by the Doctoral School board