qwViz is a software package for interactive visualisation of the time-evolution of quantum walks on arbitrarily complex graphs. The package is written in C and uses OpenGL to generate graphics in real-time. The qwViz package can be used to directly simulate discrete-time quantum walks on undirected graphs when provided with the adjacency matrix of the graph. For more detailed studies, qwViz can also be used to visualise externally generated quantum walk data written in an XML-based file format (QWML). Various aspects of the visualisation can be customised and manipulated in real-time, allowing quantum walk dynamics to be probed at various length and time scales.
Program title: qwViz
Catalogue identifier: AEJN-v1-0
Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEJN-v1-0.html
Program obtainable from: CPC Program Library, Queens University, Belfast, N. Ireland
Licensing provisions: GNU General Public Licence version 3
No. of lines in distributed program, including test data, etc.: 42 881
No. of bytes in distributed program, including test data, etc.: 97 152
Distribution format: tar.gz
Programming language: C Computer: 32-bit and 64-bit workstation
Operating system: Linux, Mac OS X 10.5 (and later)
RAM: Depends on size of graph, typically less than 50 MB
Classification: 4.15, 14
External routines: OpenGL, GLUT, Graphviz 
Nature of problem: Simulation and visualisation of quantum walks on arbitrarily complex undirected graphs.
Solution method: The program uses OpenGL to produce 3D visualisations of time-dependent probability distributions arising from quantum walks on graphs. Graph layouts are automatically generated using Graphviz libraries.
Restrictions: Graph layouts are two-dimensional, with the third spatial dimension being used to represent the probability of finding the quantum walker at a certain location.
Unusual features: The software can be used in active or dual-stereo modes for 3D visualisation of quantum walks. Images and image sequences for movies can be exported in TIFF and TGA formats.
Additional comments: Examples of various input files and an XML schema are provided. Source codes written in C and Fortran are also supplied for generating QWML files from external quantum walk simulations.
Running time: Computing quantum walk data and graph layout for a 500-step quantum walk on a fifth-generation Sierpinski gasket (366 vertices) took less than 2 seconds on a 2.53 GHz Intel Core 2 Duo processor with 4 GB of RAM and 3 MB L2 shared cache under Mac OS X 10.6.6. The same simulation for a hyper-branched fractal with 1331 vertices took less than 25 seconds. GNU C compiler with optimisation option -O2 was used for these tests. Once data has been computed, the interactive visualisation can be manipulated in real-time.
References: J. Ellson, E. Gansner, E. Koutsofios, S. North, G. Woodhull, Graphviz and dynagraph - static and dynamic graph drawing tools, in: M. Junger, P. Mutzel (Eds.), Graph Drawing Software, Springer-Verlag, 2003, pp. 127-148.
- 3D graphics
- graph drawing
- quantum walk