Circuit Simulator including Josephson Junctions in Python

PyJJASim requires numpy, scipy and matplotlib

pip install pyjjasim

PyJJASim is a circuit simulator including Josephson Junctions as components, intended to be used on large Josephson Junction Arrays (JJAs).

PyJJASim is specialized in keeping track of Josephson vortices in the circuit. It can also compute static configurations that have vortices at desired locations in the circuit.

This requires that the circuit is a planar embedding (in 2D), such that one can unambiguously refer to faces of the circuit, and vortices reside at faces. This imposes that nodes in the circuit must be placed at 2D coordinates, and that no junctions can cross. This also means no hierarchical structure is supported.

• supports basic components (inductors, resistors, capacitors and current- and voltage sources)
• keep track of (and place) Josephson vortices in the circuit
• compute static configurations
• determine dynamic stability of static configurations
• maximize parameters that have stable static configurations
• compute time evolutions
• define external magnetic flux through each face
• thermal fluctuations modeling nonzero temperature
• visualization and animation of simulation results

tutorial
API
article (in preparation for submission)

from pyjjasim import *

sq_array = SquareArray(10, 10)
problem = StaticProblem(sq_array, frustration=0.1)
config, status, info = problem.compute()
config.plot(node_quantity="phi")

Program output:

n = np.zeros(sq_array.face_count())
n[sq_array.locate_faces(x=[2.5,6.5], y=[2.5,6.5])] = 1
config, status, info = problem.new_problem(vortex_configuration=n).compute()
config.plot(node_quantity="phi")
plt.show()

Program output:

More examples:

figure 1: Example of a frustrated honeycomb array with horizontal current bias. Snapshot of a time evolution; the vortices are drifting downward. The electric potential gradually increases in the direction of the external current (see examples/images/biassed_honeycomb.py).

figure 2: Example of giant Shapiro steps in a square array. The external current has a DC and AC component causing resonance in the form of voltage plateaus (see examples/images/shapiro_steps.py).

figure 3: Example of a disordered array with different types of Josephson vortices (see examples/images/disordered.py).

If you have any questions, comments, complaints, bug reports, feature requests, etc. please contact me at m.lankhorst89@gmail.com!