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Just another quantum simulator.

JAQSI is a JAX-based quantum circuit simulator for gates and pulses. Circuits are Python functions that record operations; Script executes them with statevector or density-matrix simulation, depending on whether they contain noise. Circuits support JAX differentiation, jit, and vmap.

To give it a try, install JAQSI with pip:

pip install jaqsi

For NVIDIA GPUs, install the appropriate CUDA extra:

pip install "jaqsi[cuda13]" # use cuda12 if needed

Once installed, define a circuit as a Python function. Gates records its operations, and Script executes it and returns the requested measurement. Here is a small one to start with; the usage guide takes it further.

import jaqsi
import jax.numpy as jnp
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)
theta = jnp.array([0.5])
script.execute(type="expval", obs=[jaqsi.PauliZ(wires=0)], args=(theta,))

Gates records gates and optional noise on the circuit tape. By default, gates run as ideal unitaries; passing pulse=True runs their pulse implementations. The same circuit can use both levels.

To go below the gate level, simulate pulses and tune their parameters with quantum optimal control.

For tools built on top of JAQSI, including quantum Fourier model ansätze, expressibility, entangling capability, and Fourier analysis, see qml-essentials.

Ideas and bug reports are welcome too; see the contribution guide.

For research citations, use "Cite this repository" on GitHub.