permute_detectors#

permute_detectors(circuit: Circuit, permutation) → Circuit[source]#

Permutes the detectors in a Stim circuit according to the given permutation.

The function moves all detectors to the end of the circuit and applies the permutation. It preserves the semantic meaning of each detector (which measurements it targets) and its spatial coordinates (compensating for SHIFT_COORDS instructions).

Parameters:

circuitstim.Circuit: The input Stim circuit. Assumed to have no REPEAT blocks.
permutationiter: An iterable of integers representing the desired order of detectors. permutation[i] = k means the i-th detector in the output should be the k-th detector from the input. E.g. (2, 1, 0) means Output_D0 = Input_D2, Output_D1 = Input_D1, Output_D2 = Input_D0.

Returns:

new_circuitstim.Circuit: A new Stim circuit with permuted detectors.

Examples

We create a circuit with three detectors. The first and third detectors are triggered by deterministic errors.

from qrisp import QuantumVariable, measure
from qrisp.jasp import extract_stim, parity
from qrisp.misc.stim_tools import stim_noise, permute_detectors
import numpy as np

@extract_stim
def detector_circuit():
    qv = QuantumVariable(3)
    # Apply deterministic noise to qv[0] and qv[2]
    stim_noise("X_ERROR", 1.0, qv[0])
    stim_noise("X_ERROR", 1.0, qv[2])

    m0 = measure(qv[0])
    m1 = measure(qv[1])
    m2 = measure(qv[2])

    # Detector 0 checks m0 (fires)
    d0 = parity(m0, expectation=0)
    # Detector 1 checks m1 (silent)
    d1 = parity(m1, expectation=0)
    # Detector 2 checks m2 (fires)
    d2 = parity(m2, expectation=0)

    return d0, d1, d2

d0_idx, d1_idx, d2_idx, stim_circ = detector_circuit()

We sample from the original circuit:

# Sample original
sampler = stim_circ.compile_detector_sampler()
print(sampler.sample(1))
# Yields: [[True, False, True]]

Now we permute the detectors using the permutation (1, 2, 0).

# Permute: (1, 2, 0)
# New D0 comes from Old D1 (False)
# New D1 comes from Old D2 (True)
# New D2 comes from Old D0 (True)
permuted_circ = permute_detectors(stim_circ, (1, 2, 0))

sampler_perm = permuted_circ.compile_detector_sampler()
print(sampler_perm.sample(1))
# Yields: [[False, True, True]]