def sim_qubit_fid(n_meas, n_meas_rep, meas_dist, n_trials=100, n_particles=1000, n_rec=15):
r"""Calculates the average fidelity of the optimal estimator (approximated
by SMC) averaged over Haar random pure states and a random sample of
measurement outcomes. The estimator is calculated at a given number of
interim times throughout the tomographic process.
:param n_meas: The number of copies of the system given in each
tomographic run
:type n_meas: Integer
:param n_meas_rep: The number of measurement outcomes to average the
fidelity over for each copy of the system in a
tomographic run
:type n_meas_rep: Integer
:param meas_dist: Object defining the distribution from which to draw
measurement directions
:type meas_dist: Object possessing `sample(n)` function that returns a
numpy.array((2, n)) of unit vectors in
:math:`\mathbb{C}^2`
:param n_trials: The number of tomographic runs (aka samples from the
pure state prior) the fidelity is averaged over
:type n_trials: Integer
:param n_particles: Number of SMC particles to use
:type n_particles: Integer
:param n_rec: Number of places to record average fidelity (on a log
scale)
:type n_rec: Integer
:returns: An array with the calculated average fidelities at the
specified times for all tomographic runs
:return type: numpy.array((n_trials, n_rec))
"""
n_qubits = 1 # This function isn't guaranteed to generalize by changing
# this value, but it is included here to aid readability and
# aid any future generalization efforts
dim = 2 * n_qubits
# Record data on a logarithmic scale
rec_idxs = np.unique(np.round(np.logspace(0, np.log10(n_meas), n_rec)))
n_rec = rec_idxs.shape[0]
# Allocate result array
fidelities = np.empty((n_trials, n_rec))
# Instantiate model and state prior
model = HaarTestModel(n_qubits=n_qubits)
prior = HaarDistribution(n_qubits=n_qubits)
# Sample all the measurement directions used at once (since some samplers
# might be more efficient doing things this way)
raw_meas_dirs = meas_dist.sample(n_trials * n_meas)
# Reshape the measurement directions to be a n_trials x n_meas array of unit
# vectors in C^2
meas_dirs = np.reshape(raw_meas_dirs.T, (n_trials, n_meas, 2))
for trial_idx in xrange(n_trials):
# Pick a random true state and instantiate the Bayes updater
true_state = prior.sample()
true_vec = model.param2vec(true_state)
updater = SMCUpdater(model, n_particles, prior, resampler=LiuWestResampler(a=0.95, h=None))
rec_idx = 0
for meas_idx in xrange(n_meas):
meas_dir = meas_dirs[trial_idx, meas_idx]
# Set the experimental parameters for the measurement
expparams = np.array([(meas_dir, n_meas_rep)], dtype=model.expparams_dtype)
# Simulate data and update
data = model.simulate_experiment(true_state, expparams)
updater.update(data, expparams)
if meas_idx + 1 in rec_idxs:
# Generate the estimated state -> average then maximal
# eigenvector
weights = updater.particle_weights
locs = updater.particle_locations
avg_state = 1j * np.zeros([dim, dim])
for idx_locs in xrange(n_particles):
psi = model.param2vec(locs[idx_locs][np.newaxis])
avg_state += weights[idx_locs] * np.outer(psi, psi.conj())
eigs = la.eig(avg_state)
max_eig = eigs[1][:, np.argmax(eigs[0])]
fidelities[trial_idx, rec_idx] = model.fidelity(true_vec, max_eig)
rec_idx += 1
# Give progress updates
print(100 * ((trial_idx + 1) / n_trials))
return fidelities
def fid_smc(n_meas, K, n_qubits=1, n_trials=100, n_particles=1000, n_rec=15):
"""
Evaluates the average fidelity incurred by using sequential Monte Carlo
(SMC) to estimate pure states.
:param n_meas: The number of copies of the system given in each
tomographic run
:type n_meas: Integer
:param K: Number of single-shot measurements
:type K: Integer
:param n_trials: Number of times to run the SMC estimation procedure.
:type n_trials: Integer
:param n_particles: Number of SMC particles to use.
:type n_particles: Integer
:param n_rec: Number of place to record data (on a log scale)
:type n_rec: Integer
:returns: Dictionary of various fidelities and timings
:return type: Dictionary
"""
dim = int(2 ** n_qubits)
# Record data on a logarithmic scale
rec_idx = np.unique(np.round(np.logspace(0, np.log10(n_meas), n_rec)))
n_rec = rec_idx.shape[0]
# Allocate arrays to hold results.
fidelity_mub = np.empty((n_trials, n_rec))
fidelity_opt = np.empty((n_trials, n_rec))
fidelity_WM = np.empty((n_trials, n_rec))
fidelity_DST = np.empty((n_trials, n_rec))
# Instantiate models and distributions
model = HaarTestModel(n_qubits=n_qubits)
prior = HaarDistribution(n_qubits=n_qubits)
measMUB = MUBDistribution()
measWM = WeakMeasDistribution(eps=0.05)
measDST = DSTDistribution(0.1)
timing = np.empty((n_trials,))
# Make and show a progress bar.
"""
prog = ProgressBar()
prog.show()
"""
for idx_trial in xrange(n_trials):
# Pick a random true state and instantiate the Bayes updater
true_state = prior.sample()
true_vec = model.param2vec(true_state)
updater_opt = SMCUpdater(model, n_particles, prior, resampler=LiuWestResampler(a=0.95, h=None))
updater_mub = SMCUpdater(model, n_particles, prior, resampler=LiuWestResampler(a=0.95, h=None))
updater_WM = SMCUpdater(model, n_particles, prior, resampler=LiuWestResampler(a=0.95, h=None))
updater_DST = SMCUpdater(model, n_particles, prior, resampler=LiuWestResampler(a=0.95, h=None))
# Record the start time.
tic = time.time()
idx_rec = 0
for idx_meas in xrange(n_meas):
# Choose a random measurement direction
foo = prior.sample()
meas_opt = model.param2vec(foo)
meas_mub = measMUB.sample()
meas_WM = measWM.sample()[:, 0]
meas_DST = measDST.sample()[:, 0]
expparams_opt = np.array([(meas_opt, K)], dtype=model.expparams_dtype)
expparams_mub = np.array([(meas_mub, K)], dtype=model.expparams_dtype)
expparams_WM = np.array([(meas_WM, K)], dtype=model.expparams_dtype)
expparams_DST = np.array([(meas_DST, K)], dtype=model.expparams_dtype)
# Simulate data and update
data_opt = model.simulate_experiment(true_state, expparams_opt)
updater_opt.update(data_opt, expparams_opt)
data_mub = model.simulate_experiment(true_state, expparams_mub)
updater_mub.update(data_mub, expparams_mub)
data_WM = model.simulate_experiment(true_state, expparams_WM)
updater_WM.update(data_WM, expparams_WM)
data_DST = model.simulate_experiment(true_state, expparams_DST)
updater_DST.update(data_DST, expparams_DST)
if idx_meas + 1 in rec_idx:
# Generate the estimated state -> average then maximal eigenvector
weights = updater_opt.particle_weights
locs = updater_opt.particle_locations
ave_state = 1j * np.zeros([dim, dim])
for idx_locs in xrange(n_particles):
psi = model.param2vec(locs[idx_locs][np.newaxis])
ave_state += weights[idx_locs] * np.outer(psi, psi.conj())
eigs = la.eig(ave_state)
max_eig = eigs[1][:, np.argmax(eigs[0])]
fidelity_opt[idx_trial, idx_rec] = model.fidelity(true_vec, max_eig)
# MUB
weights = updater_mub.particle_weights
locs = updater_mub.particle_locations
ave_state = 1j * np.zeros([dim, dim])
for idx_locs in xrange(n_particles):
psi = model.param2vec(locs[idx_locs][np.newaxis])
ave_state += weights[idx_locs] * np.outer(psi, psi.conj())
eigs = la.eig(ave_state)
max_eig = eigs[1][:, np.argmax(eigs[0])]
fidelity_mub[idx_trial, idx_rec] = model.fidelity(true_vec, max_eig)
# Weak Measurement
weights = updater_WM.particle_weights
locs = updater_WM.particle_locations
ave_state = 1j * np.zeros([dim, dim])
for idx_locs in xrange(n_particles):
psi = model.param2vec(locs[idx_locs][np.newaxis])
ave_state += weights[idx_locs] * np.outer(psi, psi.conj())
eigs = la.eig(ave_state)
max_eig = eigs[1][:, np.argmax(eigs[0])]
fidelity_WM[idx_trial, idx_rec] = model.fidelity(true_vec, max_eig)
# DST Measurement
weights = updater_DST.particle_weights
locs = updater_DST.particle_locations
ave_state = 1j * np.zeros([dim, dim])
for idx_locs in xrange(n_particles):
psi = model.param2vec(locs[idx_locs][np.newaxis])
ave_state += weights[idx_locs] * np.outer(psi, psi.conj())
eigs = la.eig(ave_state)
max_eig = eigs[1][:, np.argmax(eigs[0])]
fidelity_DST[idx_trial, idx_rec] = model.fidelity(true_vec, max_eig)
idx_rec += 1
# Record how long it took us.
timing[idx_trial] = time.time() - tic
print(100 * ((idx_trial + 1) / n_trials))
# prog.value = 100 * ((idx_trial + 1) / n_trials)
return {
"fidelity_opt": fidelity_opt,
"fidelity_mub": fidelity_mub,
"fidelity_WM": fidelity_WM,
"fidelity_DST": fidelity_DST,
"timing": timing,
}
