Density matrix simulator not applying kraus operators

The latest version of the qvm seems to be not applying Kraus operators during density matrix simulations.

With qvm 1.9.0, the script below gives [0.6222487943248762]. However with qvm 1.17.1 and 1.15.3 it gives [-1.0], which is what you'd expect in the absence of noise.

from pyquil.api import QVMConnection
from pyquil.api._base_connection import post_json

program = """
DEFGATE NOISY-CHANNEL:
    1.0, 0
    0, 1.0

PRAGMA ADD-KRAUS NOISY-CHANNEL 0 "(0.770997925690323 0.0 0.0 0.3350743172676877)"
PRAGMA ADD-KRAUS NOISY-CHANNEL 0 "(0.6368376548078946 0.0 0.0 -0.27676850388936003)"
PRAGMA ADD-KRAUS NOISY-CHANNEL 0 "(0.0 0.6943795815880344 0.0 0.0)"
PRAGMA ADD-KRAUS NOISY-CHANNEL 0 "(0.0 -0.5735515616194105 0.0 0.0)"
PRAGMA ADD-KRAUS NOISY-CHANNEL 1 "(0.770997925690323 0.0 0.0 0.3350743172676877)"
PRAGMA ADD-KRAUS NOISY-CHANNEL 1 "(0.6368376548078946 0.0 0.0 -0.27676850388936003)"
PRAGMA ADD-KRAUS NOISY-CHANNEL 1 "(0.0 0.6943795815880344 0.0 0.0)"
PRAGMA ADD-KRAUS NOISY-CHANNEL 1 "(0.0 -0.5735515616194105 0.0 0.0)"
X 0
NOISY-CHANNEL 0
"""
payload = {'type': "expectation",
           'state-preparation': program,
           'operators': ['Z 0']}

qvm = QVMConnection(endpoint='http://127.0.0.1:5000')
response = post_json(qvm.session, qvm.sync_endpoint+"/qvm", payload)
print(response.json())

quil-lang / qvm

Density matrix simulator not applying kraus operators #259