Noise¶
Real quantum devices are noisy -- this guide shows you how to add noise (Kraus) channels to a squint
circuit
from squint.ops.dv import DiscreteVariableState, HGate, CXGate
from squint.ops.noise import DepolarizingChannel
def create_noisy_sensor(n_qubits, p=0.1):
"""Create a quantum sensor with depolarizing noise."""
circuit = Circuit(backend="mixed") # Use mixed state backend for noise
# Initialize qubits
for i in range(n_qubits):
circuit.add(DiscreteVariableState(wires=(i,), n=(0,)))
# GHZ preparation with noise
circuit.add(HGate(wires=(0,)))
circuit.add(DepolarizingChannel(wires=(0,), p=noise_strength))
for i in range(1, n_qubits):
circuit.add(CXGate(wires=(0, i)))
# Add noise after each two-qubit gate
circuit.add(DepolarizingChannel(wires=(0,), gamma=noise_strength))
circuit.add(DepolarizingChannel(wires=(i,), gamma=noise_strength))
# Phase sensing
for i in range(n_qubits):
circuit.add(RZGate(wires=(i,), phi=0.0), f"phase_{i}")
# Measurement
for i in range(n_qubits):
circuit.add(HGate(wires=(i,)))
return circuit