Constrain piece-wise constant pulses to vary smoothly

import matplotlib.pyplot as plt
import numpy as np

from paraqeet.measurement.smoothness import Smoothness
from paraqeet.optimization_map import OptimizationMap
from paraqeet.optimizers.scipy_optimizer_gradient import ScipyOptimizerGradient
from paraqeet.quantity import Quantity
from paraqeet.signal.envelopes import GaussEnvelope
from paraqeet.signal.pwc_generator import PWCGenerator

delta_sampling = 33e-9
n_pwc = 40  # number of piecewise constants in the pulse
t_final = n_pwc * delta_sampling  # for now just set up for trying
tlist = np.linspace(0, t_final, n_pwc + 1)
eps_qubit = 2 * np.pi * 1.0  # initial amplitude of the qubit (in MHz)
eps_max_qubit = 5 * eps_qubit  # maximum amplitude of the resonator (in MHz)
tone_qubit = GaussEnvelope(
    amplitude=Quantity(eps_qubit * 1e6, -eps_max_qubit * 1e6, eps_max_qubit * 1e6),
    t_final=Quantity(t_final, 1 / 2 * t_final, 2 * t_final),
)
gen_qubit = PWCGenerator(envelopes=[tone_qubit], max_amplitude=eps_max_qubit * 1e6, tlist=tlist)

from plotting import plot_signal

ts = np.linspace(0, t_final, 501)
fig, ax = plt.subplots(1, figsize=(5, 3))
plot_signal(tone_qubit, ts, ax, linestyle="-", label="Smooth")
plot_signal(gen_qubit, ts, ax, linestyle="--", label="PWC")
ax.legend(loc=1, frameon=True)
plt.show()

optmap = OptimizationMap()
optmap.add(gen_qubit, gen_qubit.get_parameters())

# We add dummy parameters to check if the gradient is computed
# correctly by padding zeros
# optmap.add(tone_qubit, tone_qubit.get_parameters())
optmap.register_params_with_optimizables()

smoothness = Smoothness(pwc_generator=gen_qubit)

We can check that the gradient has the correct shape

print(smoothness.get_value_and_gradient(tlist)[1].shape)

(80,)

opt = ScipyOptimizerGradient(smoothness, optimization_map=optmap)
max_iter = 200
opt.set_options({"maxiter": max_iter})

opt.optimize(ts)

{'status': 1, 'value': 1.1649151643311484e-09, 'iterations': 20, 'message': 'CONVERGENCE: NORM OF PROJECTED GRADIENT <= PGTOL'}

smoothness.measure(ts)

0.9999999988350848

smoothness.get_value_and_gradient(ts)

(0.9999999988350848,
 Array([-1.00058440e-14,  2.15090019e-13, -1.21393925e-13, -3.56757831e-14,
         4.32685927e-14, -9.68587243e-14, -4.40413453e-14, -1.06365887e-14,
         1.05700111e-13, -1.52029507e-13,  4.58424060e-14, -7.35246762e-14,
        -3.52732230e-14,  7.81778245e-14,  7.35808110e-14,  8.99784498e-14,
         6.62109772e-14,  1.02326266e-14, -5.34368855e-14, -9.52053143e-14,
        -9.52053143e-14, -5.34368855e-14,  1.02326266e-14,  6.62109772e-14,
         8.99784498e-14,  7.35808110e-14,  7.81778245e-14, -3.52732230e-14,
        -7.35246762e-14,  4.58424060e-14, -1.52029507e-13,  1.05700111e-13,
        -1.06365887e-14, -4.40413453e-14, -9.68587243e-14,  4.32685927e-14,
        -3.56757831e-14, -1.21393925e-13,  2.15090019e-13, -1.00058440e-14,
        -0.00000000e+00, -0.00000000e+00, -0.00000000e+00, -0.00000000e+00,
        -0.00000000e+00, -0.00000000e+00, -0.00000000e+00, -0.00000000e+00,
        -0.00000000e+00, -0.00000000e+00, -0.00000000e+00, -0.00000000e+00,
        -0.00000000e+00, -0.00000000e+00, -0.00000000e+00, -0.00000000e+00,
        -0.00000000e+00, -0.00000000e+00, -0.00000000e+00, -0.00000000e+00,
        -0.00000000e+00, -0.00000000e+00, -0.00000000e+00, -0.00000000e+00,
        -0.00000000e+00, -0.00000000e+00, -0.00000000e+00, -0.00000000e+00,
        -0.00000000e+00, -0.00000000e+00, -0.00000000e+00, -0.00000000e+00,
        -0.00000000e+00, -0.00000000e+00, -0.00000000e+00, -0.00000000e+00,
        -0.00000000e+00, -0.00000000e+00, -0.00000000e+00, -0.00000000e+00],      dtype=float64))

plot_signal(gen_qubit, ts, linestyle="--", label="PWC");

As expected obtain a flat pulse.