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Just another quantum simulator.

JAQSI is a gate- and pulse-level quantum circuit simulator built on JAX. Circuits are plain Python functions that record operations onto a tape; the Script class compiles and executes them, routing between statevector and density-matrix simulation automatically depending on whether noise channels are present. Everything is pure JAX, so circuits are differentiable, jit-able and vmap-able out of the box.

Curious? Installing this package is as simple as with any other package

pip install jaqsi

or with the uv package manager:

uv add jaqsi

Once you have set things up, go ahead and checkout how to use JAQSI.

import jaqsi
from jaqsi import Gates

def circuit(theta):
    Gates.RX(theta[0], wires=0)
    Gates.CX(wires=[0, 1])

script = jaqsi.Script(circuit, n_qubits=2)
script.execute(type="expval", obs=[jaqsi.PauliZ(wires=0)], args=(theta,))

Gates is the entry point for applying gates: it records them on the circuit tape, attaches any noise you ask for, and runs them as ideal unitaries or, with pulse=True, as real pulses.

Beyond gate-level simulation, JAQSI can simulate circuits at the pulse level and tune pulse parameters with quantum optimal control.

If you are looking for quantum Fourier model tooling built on top of this simulator (ansaetze, expressibility, entangling capability and Fourier analysis), see qml-essentials.

If you want to contribute, please refer to our CONTRIBUTING guide on Github.

Do you want to use our software in a research project? Please checkout the github repository and follow the instructions ("Cite this repository") there.