Mailman 3 - Kwant-announce

by Christoph Groth

Kwant 1.4.1 has been released recently. By now the new version should be available on all usual channels. This maintenance release does not introduce any new functionality, but fixes some backwards compatibility issues that were introduced by 1.4.0. Most notably, Kwant 1.4.1 is more tolerant to scripts that use the now deprecated "args" mechanism of passing parameters. For example, value functions may continue to accept *args or **kwargs as long as the new "params" parameter-passing mechanism is not used. Please see the "what's new" document [1] for a detailed list of changes. [1] https://kwant-project.org/doc/1/pre/whatsnew/1.4#changes-in-kwant-1-4-1

1 year, 9 months

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Kwant 1.4 has been released

by Christoph Groth

We are pleased to announce the release of Kwant 1.4, the result of a year and a half of development. Highlights of the new release: * Adding magnetic field to systems, even in complicated cases, is now specially supported. * The KPM module can now calculate conductivities. * The `Qsymm library <https://gitlab.kwant-project.org/qt/qsymm>`_ for Hamiltonian symmetry analysis has been integrated. * The handling of system parameters has been improved and optimized. * Plotting has been improved, most notably through the addition of a routine that plots densities with interpolation. * Installing Kwant on Windows is now much easier thanks to Conda packages. All these and other improvements that are detailed in the "what's new in Kwant 1.4" document [1]. The new version is practically 100% backwards-compatible with scripts written for previous versions of Kwant 1.x. The following people contributed code to this release: * Anton Akhmerov * Paul Clisson * Christoph Groth * Thomas Kloss * Bas Nijholt * Pablo Pérez Piskunow * Tómas Örn Rosdahl * Rafał Skolasiński * Dániel Varjas * Joseph Weston We would like to hear your feedback at kwant-discuss(a)kwant-project.org. [1] https://kwant-project.org/doc/1.4/pre/whatsnew/1.4

1 year, 12 months

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Kwant 1.3 has been released

by Christoph Groth

After more than one year of development, we are extremely pleased to announce the release of Kwant 1.3. Kwant 1.3 supports * discretizing of continuum Hamiltonians, * calculating and displaying local densities and currents, * declaring and using symmetries and conservation laws, * calculating bulk properties using the kernel polynomial method, * finalizing builders with multiple translational symmetries, and has many other improvements that are detailed in the "what's new in Kwant 1.3" document [1]. The installation instructions [2] have been updated to explain how to install Kwant 1.3 on computers running GNU/Linux, Mac OS, and Windows. Note that thanks to the package manager Conda it is now much easier to install Kwant under Mac OS and on Unix accounts without root privileges. The new version is practically 100% backwards-compatible with scripts written for previous versions of Kwant 1.x. The Kwant team is happy to welcome Joseph Weston as a member. We are also grateful to the many contributors without whom this release would not be nearly as good: * Jörg Behrmann * Bas Nijholt * Michał Nowak * Viacheslav Ostroukh * Pablo Pérez Piskunow * Tómas Örn Rosdahl * Sebastian Rubbert * Rafał Skolasiński * Adrien Sorgniard We would like to hear your feedback at kwant-discuss(a)kwant-project.org. [1] https://kwant-project.org/doc/1.3/pre/whatsnew/1.3 [2] https://kwant-project.org/install

3 years, 9 months

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Kwant-based tutorial: try it directly in your web browser

by Christoph Groth

Dear users of Kwant, At this year’s APS March meeting the core Kwant team held an “Introduction to Computational Quantum Nanoelectronics” tutorial [1]. The bulk of the course consisted of hand-on work with Kwant-powered Jupyter notebooks that contain explanations, examples and exercises. The tutorial was attended by over 70 people and we received highly positive feedback for it. The complete set of the tutorial notebooks is now available online [2]. There is also a link that allows to execute the notebooks directly in a web browser without installing Kwant locally. Please feel free to check it out and do not hesitate to spread the word to anyone who might be interested, especially to people who are not using Kwant yet. Regards, Christoph on behalf of the whole tutorial team [1] http://www.aps.org/meetings/march/events/tutorials.cfm#t10 [2] http://kwant-project.org/mm16

4 years, 10 months

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Kwant 1.2 has been released

by Christoph Groth

Hello, We are happy to announce the release of Kwant 1.2 [1]. Kwant 1.2 is identical to Kwant 1.1 except that it has been updated to run on Python 3.4 and above. Bugfix releases for the 1.1 and 1.2 series will mirror each other, i.e. 1.1.3 and 1.2.3 will fix the same bugs. Starting with Kwant 1.2, all Kwant development will target Python 3. We plan, however, to maintain Python 2 support with the 1.1 series for several years. At this moment, Kwant 1.2 packages are available [2] for: Debian, Ubuntu & Windows. Arch Linux and Mac are not ready yet, but will hopefully follow soon. Please do report any problems (especially with installation) that you may encounter with the new version. Thanks to everyone who contributed to this release! Happy kwanting, Christoph on behalf of the Kwant team [1] http://kwant-project.org/doc/1/pre/whatsnew/1.2 [2] http://kwant-project.org/install

5 years, 2 months

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APS March meeting 2016 tutorial: Introduction to computational quantum nanoelectronics

by Christoph Groth

Dear all, This is an announcement for an APS March meeting 2016 tutorial that will feature Kwant. It can be also found online: http://www.aps.org/meetings/march/events/tutorials.cfm#t10 Please spread the word to anyone who might be interested. Christoph Tutorial #10: Introduction to Computational Quantum Nanoelectronics Quantum nanoelectronics deals with the physics of small (< 1 μm) and/or cold (down to ~10 mK) objects connected to the macroscopic world through electrodes or gates. A central question at the core of this field is how quantum effects can be observed and manipulated through the macroscopic measuring apparatus. In this tutorial, we will give a pedagogical introduction to the field. We will start with an introduction to the main theoretical concepts and a review of some seminal experiments. The central part of the tutorial will be devoted to practical training on numerical calculations: we will demonstrate how researchers can simply setup their own models and perform their own calculations. These calculations can be used for theoretical predictions, to explain experimental data or even to assist the conception of device design. The numerical part of the lecture is based on the Python programming language and the Kwant package. No particular background in programming is needed. Topics • Scattering theory of transport, Landauer formula for the conductance • Continuous and discrete models (effective mass, Dirac equation, fermion doubling theorem) • Electronic interference effects (Aharonov-Bohm effect, universal conductance fluctuations) • Topological matter, quantum Hall effect • Time-resolved nanoelectronics • Numerical calculations with Python • Hands-on tutorial on Kwant • Practical example of the modeling of an experiment When? Sunday, March 13, 2016 1:30 p.m. - 5:30 p.m. Who Should Attend? PhDs, postdocs, and faculty (both experimentalists and theorists) interested in calculating the transport properties of quantum nano-systems (nanowires, semiconducting heterostructures, graphene, topological insulators…). We particularly encourage participation of experimentalists wanting to develop their own modeling of their experiments. Basic knowledge of quantum mechanics, statistical physics and condensed matter would help to fully benefit from the tutorial. Organizer Christoph Groth, CEA Grenoble, France Instructors • Anton Akhmerov, TU Delft, Netherlands • Christoph Groth, CEA Grenoble, France • Xavier Waintal, CEA Grenoble, France • Michael Wimmer, TU Delft, Netherlands

5 years, 4 months

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Kwant 1.1 has been released

by Christoph Groth

Hello, We are happy to announce the release of Kwant 1.1. The user-visible changes are: • Harmonize Bands with modes • New option add_cells of attach_lead • New method conductance_matrix • Deduction of transmission probabilities • Clearer error messages • New option pos_transform of map See [1] for details. There is nothing spectacular here, but particularly the improved error messages should make work with Kwant more pleasant. There was also substantial work “under the hood” that will allow us to release new versions with much less effort in the future. Full backward compatibility is the aim for all Kwant releases that share the same major version. Thus, all Kwant 1.0 scripts should continue to work with Kwant 1.1. Kwant 1.1 packages are available right now for Debian, Ubuntu, and Windows. They should be available soon for Mac OS & Arch Linux. Please let us know if you experience any problems. The plan is that 1.1 will be the last Kwant release for Python 2 and we switch development to Python 3. There should be soon a Kwant 1.2 that will be identical to 1.1 except that it will use Python 3. (Do not worry if you have to keep using Python 2: we plan to maintain Kwant 1.1 for several years.) Thanks to everyone who contributed to this release! Happy kwanting, Christoph on behalf of the Kwant team [1] http://kwant-project.org/doc/1.1/pre/whatsnew/1.1

5 years, 4 months

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Kwant 1.1 has been released

by Christoph Groth

Hello, We are happy to announce the release of Kwant 1.1. The user-visible changes are: • Harmonize Bands with modes • New option add_cells of attach_lead • New method conductance_matrix • Deduction of transmission probabilities • Clearer error messages • New option pos_transform of map See [1] for details. There is nothing spectacular here, but particularly the improved error messages should make work with Kwant more pleasant. There was also substantial work “under the hood” that will allow us to release new versions with much less effort in the future. Full backward compatibility is the aim for all Kwant releases that share the same major version. Thus, all Kwant 1.0 scripts should continue to work with Kwant 1.1. Kwant 1.1 packages are available right now for Debian, Ubuntu, and Windows. They should be available soon for Mac OS & Arch Linux. Please let us know if you experience any problems. The plan is that 1.1 will be the last Kwant release for Python 2 and we switch development to Python 3. There should be soon a Kwant 1.2 that will be identical to 1.1 except that it will use Python 3. (Do not worry if you have to keep using Python 2: we plan to maintain Kwant 1.1 for several years.) Thanks to everyone who contributed to this release! Happy kwanting, Christoph on behalf of the Kwant team [1] http://kwant-project.org/doc/1.1/pre/whatsnew/1.1

5 years, 4 months

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2 PhD positions in computational quantum theory (Grenoble)

by Christoph Groth

Dear all, Please take note of this announcement and forward it to anyone who might be interested. Thank you. This summer/fall we are going to hire two PhD students to work with us on new computational approaches to quantum transport. Candidates should have a strong background in theoretical physics (ideally condensed matter / quantum transport) as well as experience in software design and development. Each PhD project will consist of three overlapping phases: (1) Prototyping of a new computational approach for quantum transport problems. (2) Implementation of the new approach within the framework of the Kwant code [1]. (3) Application of the newly gained capabilities to unsolved physical problems, in close collaboration with experts in the particular fields. The two subjects are introduced in some detail at the bottom of this message. The research will take place at the Institute for Nanoscience and Cryogenics (INAC) of CEA Grenoble (France) over the course of three years under the supervision of Christoph Groth and Xavier Waintal in close collaboration with Michael Wimmer and Anton Akhmerov of Delft University of Technology (Netherlands). The city of Grenoble offers a superb combination of a rich international scientific environment with a unique natural and cultural setting. Grenoble is home to a vibrant nanoscience research community [2], several international research institutions (ESRF synchrotron, ILL neutron source, and others) and 60,000 university students. The city is literally surrounded by the French alps that offer numerous possibilities for outdoor activities. Interested candidates are invited to send an application to Christoph Groth [3] with the subject “PhD application Kwant 2015”. Applications should include: • a CV, • Email addresses of persons that can be asked for a recommendation, • an example of theoretical physical work done by the applicant (e.g. a project, or a master thesis), Applicants are invited to also provide the source code of a program that highlights their software engineering experience. Sincerely Christoph Groth and Xavier Waintal [1] http://kwant-project.org/ [2] http://www.fondation-nanosciences.fr/RTRA/en/14/vocation.html [3] mailto:christoph.groth@cea.fr Subject 1: Scalable electrostatics computations Both single-particle simulations of quantum nanoelectronics and pure electrostatics simulations are a standard problem. However, in order to accurately simulate complex quantum systems, one needs to combine both approaches. This transforms the linear electrostatic problem into a non-linear integro-differential system of equations with rapidly growing complexity. Current approaches at exactly solving the combined problem are limited to small systems of around 10 nanometers in linear size. Advancing the state of the art is becoming increasingly important to improve our understanding of modern experiments (e.g. spin qubits, mesoscale transport). Subject 2: Multidimensional scattering Traditionally, quantum transport codes have focused on the 1-d scattering problem: a finite scattering region with attached semi-infinite quasi-1-d electrodes. While this suffices to calculate the basic experimental observables (for example conductance), solving the more general n-dimensional case would allow to • characterize disordered materials with a non-spherical band structure, • calculate transport properties of crystallographic defects, • treat hybrid systems with different dimensionalities (e.g. a 1-d nanowire coupled to a 3-d superconductor). The first two capabilities would greatly aid in the analysis of realistic systems and materials that in practice contain disorder, dislocations and impurities. The last capability would be highly valuable for example for studies of Majorana fermions.

5 years, 8 months

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Kwant user survey

by Christoph Groth

Dear all, We have prepared a short (5 min) anonymous survey for users of Kwant. Please consider helping us by filling it out and do not hesitate to spread the word to others who might not be on this list. The survey is linked from the top of http://kwant-project.org/. It can be also accessed directly at http://kwant-project.org/2015-survey. Thanks, your feedback is highly appreciated. Christoph on behalf of the authors of Kwant

5 years, 9 months

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