Density Matrix Module for SQUANDER
Provides mixed-state quantum simulation with noise modeling.
Integrated as a subpackage of SQUANDER.
Usage:
from squander.density_matrix import DensityMatrix, NoisyCircuit
from squander.density_matrix import DepolarizingChannel
Example:
# Create 2-qubit density matrix
rho = DensityMatrix(qbit_num=2)
# Create circuit
circuit = NoisyCircuit(2)
circuit.add_H(0)
circuit.add_CNOT(1, 0)
# Apply circuit
import numpy as np
circuit.apply_to(np.array([]), rho)
# Add noise
noise = DepolarizingChannel(qbit_num=2, error_rate=0.01)
noise.apply(rho)
print(f"Purity: {rho.purity()}")
