Ren Xi-Jun

Job/Title:

Prof.

Primary Category:

Visiting Scientists

Discipline:

Condensed Matter Physics

Interests:

Atomic, Molecular and Optical Physics

Office:

Danciger B 222

Phone:

02 6586 355

E-Mail:

Upcoming Events

Monday, December 23rd

Physics Colloquium : "Trapped-ion quantum computing: a tale of highly social qubits"
- Start time: 12:00pm
- End date: Monday, December 23rd
- End time: 01:30pm
- Lecturer: Roee Ozeri, Weizmann InstituteAbstract:The fields of quantum computing and quantum simulation are undergoing rapid progress, with various technologies (qubit modalities) competing for quantum advantage and performance. In this talk I will review one of the leading quantum platforms: trapped ion qubits and will describe its state-of the art. In particular I will focus on one of the main advantages of trapped-ion qubits, namely their long-range Coulomb interaction and the all-to-all qubit connectivity it enables. I will present several of our experiments in which the global phonon spectrum of an ion crystal was used to generate programable couplings between qubits and quantum simulations of Hamiltonians with broken time-reversal symmetry. All these techniques culminate in a proposal for a unique scale-up architecture for large-scale trapped-ion quantum computers.
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Tuesday, December 24th

Astrolunch: Allard Jan van Marle
- Start time: 12:30pm
- End date: Tuesday, December 24th
- End time: 01:30pm
- Speaker: Dr. Allard Jan van Marle (Extreme Light Infrastructure ERIC, ELI Beamlines Facility, Dolní Břežany, Czech Republic)Title: Using PIC-MHD to model particle acceleration in astrophysical shocksAbstract:When modelling the behaviour of astrophysical plasmas, we run into a fundamental computational problem. One can treat the plasma as a fluid using traditional grid-based magnetohydrodynamics (MHD) or, alternatively, describe the plasma as a collection of individual particles using particle-in-cell (PIC). However, both methods have limitations. MHD is computationally efficient but achieves this efficiency by describing the plasma in terms of averages. Therefore, it cannot model any interaction that requires microphysics. Nor can it handle a plasma that is not in local thermal equilibrium. By contrast, PIC does include microphysics and can handle any plasma, irrespective of whether it is in equilibrium. However, it buys this ability at a high computational cost and, as a result, requires considerable support to model even small structures. Several methods have been introduced to solve this issue. Here I will demonstrate the concept of PIC-MHD, which treats the plasma as a superposition of a thermal plasma, described through MHD; and a small, non-thermal component, treated through PIC. Using this method, we have explored 2-D and 3-D models of parallel shocks and the influence of shock obliquity on the acceleration process. Currently, we are in the process of extending the method to cover relativistic shocks to cover a wider range of astrophysical phenomena.Zoom link:https://huji.zoom.us/j/83482274870?pwd=VjEz4G7wbN7sU1a7TO0s9ReuPbPBLu.1Meeting ID: 834 8227 4870Passcode: 005622 Contact: Nir Shaviv
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Ren Xi-Jun