# Repository: https://gitlab.com/quantify-os/quantify-scheduler
# Licensed according to the LICENCE file on the main branch
"""
Contains function to generate most basic waveforms.
These functions are intended to be used to generate waveforms defined in the
:mod:`~quantify_scheduler.operations.pulse_library`.
Examples of waveforms that are too advanced are flux pulses that require knowledge of
the flux sensitivity and interaction strengths and qubit frequencies.
"""
from __future__ import annotations
import warnings
from typing import List, Optional, Union
import numpy as np
from scipy import interpolate, signal
[docs]
def square(t: Union[np.ndarray, List[float]], amp: Union[float, complex]) -> np.ndarray:
"""Generate a square pulse."""
return amp * np.ones(len(t))
[docs]
def square_imaginary(
t: Union[np.ndarray, List[float]], amp: Union[float, complex]
) -> np.ndarray:
"""Generate a square pulse with imaginary amplitude."""
return square(t, 1j * amp)
[docs]
def ramp(t, amp, offset=0) -> np.ndarray:
"""Generate a ramp pulse."""
return np.linspace(offset, amp + offset, len(t), endpoint=False)
[docs]
def staircase(
t: Union[np.ndarray, List[float]],
start_amp: Union[float, complex],
final_amp: Union[float, complex],
num_steps: int,
) -> np.ndarray:
"""
Ramps from zero to a finite value in discrete steps.
Parameters
----------
t
Times at which to evaluate the function.
start_amp
Starting amplitude.
final_amp
Final amplitude to reach on the last step.
num_steps
Number of steps to reach final value.
Returns
-------
:
The real valued waveform.
"""
amp_step = (final_amp - start_amp) / (num_steps - 1)
t_arr_plateau_len = int(len(t) // num_steps)
waveform = np.array([])
for i in range(num_steps):
t_current_plateau = t[i * t_arr_plateau_len : (i + 1) * t_arr_plateau_len]
waveform = np.append(
waveform,
square(
t_current_plateau,
i * amp_step,
)
+ start_amp,
)
t_rem = t[num_steps * t_arr_plateau_len :]
waveform = np.append(waveform, square(t_rem, final_amp))
return waveform
[docs]
def soft_square(t, amp):
"""
A softened square pulse.
Parameters
----------
t :
Times at which to evaluate the function.
amp :
Amplitude of the pulse.
"""
data = square(t, amp)
if len(t) > 1:
window = signal.windows.hann(int(len(t) / 2))
data = signal.convolve(data, window, mode="same") / sum(window)
return data
[docs]
def chirp(t: np.ndarray, amp: float, start_freq: float, end_freq: float) -> np.ndarray:
r"""
Produces a linear chirp signal.
The frequency is determined according to the
relation:
.. math:
f(t) = ct + f_0,
c = \frac{f_1 - f_0}{T}
The waveform is produced simply by multiplying with a complex exponential.
Parameters
----------
t
Times at which to evaluate the function.
amp
Amplitude of the envelope.
start_freq
Start frequency of the Chirp.
end_freq
End frequency of the Chirp.
Returns
-------
:
The complex waveform.
"""
chirp_rate = (end_freq - start_freq) / (t[-1] - t[0])
return amp * np.exp(1.0j * 2 * np.pi * (chirp_rate * t / 2 + start_freq) * t)
[docs]
def drag(
t: np.ndarray,
G_amp: float,
D_amp: float,
duration: float,
nr_sigma: float,
sigma: float | int | None = None,
phase: float = 0,
subtract_offset: str = "average",
) -> np.ndarray:
r"""
Generates a DRAG pulse consisting of a Gaussian :math:`G` as the I- and a
Derivative :math:`D` as the Q-component (:cite:t:`motzoi_simple_2009` and
:cite:t:`gambetta_analytic_2011`).
All inputs are in s and Hz.
phases are in degree.
:math:`G(t) = G_{amp} e^{-(t-\mu)^2/(2\sigma^2)}`.
:math:`D(t) = -D_{amp} \frac{(t-\mu)}{\sigma} G(t)`.
.. note:
One would expect a factor :math:`1/\sigma^2` in the prefactor of
:math:`D(t)`, we absorb this in the scaling factor :math:`D_{amp}` to
ensure the derivative component is scale invariant with the duration of
the pulse.
Parameters
----------
t
Times at which to evaluate the function.
G_amp
Amplitude of the Gaussian envelope.
D_amp
Amplitude of the derivative component, the DRAG-pulse parameter.
duration
Duration of the pulse in seconds.
nr_sigma
After how many sigma the Gaussian is cut off.
sigma
Width of the Gaussian envelope. If None, it is calculated with nr_sigma, which is set to 4.
phase
Phase of the pulse in degrees.
subtract_offset
Instruction on how to subtract the offset in order to avoid jumps in the
waveform due to the cut-off.
- 'average': subtract the average of the first and last point.
- 'first': subtract the value of the waveform at the first sample.
- 'last': subtract the value of the waveform at the last sample.
- 'none', None: don't subtract any offset.
Returns
-------
:
complex waveform
"""
mu = t[0] + duration / 2
if sigma is not None and nr_sigma is not None:
raise ValueError(
"Both sigma and nr_sigma are specified. Please specify only one."
)
if sigma is None:
sigma = duration / (2 * nr_sigma)
gauss_env = G_amp * np.exp(-(0.5 * ((t - mu) ** 2) / sigma**2))
deriv_gauss_env = -D_amp * (t - mu) / sigma * gauss_env
# Subtract offsets
if subtract_offset.lower() == "none" or subtract_offset is None:
# Do not subtract offset
pass
elif subtract_offset.lower() == "average":
gauss_env -= (gauss_env[0] + gauss_env[-1]) / 2.0
deriv_gauss_env -= (deriv_gauss_env[0] + deriv_gauss_env[-1]) / 2.0
elif subtract_offset.lower() == "first":
gauss_env -= gauss_env[0]
deriv_gauss_env -= deriv_gauss_env[0]
elif subtract_offset.lower() == "last":
gauss_env -= gauss_env[-1]
deriv_gauss_env -= deriv_gauss_env[-1]
else:
raise ValueError(
'Unknown value "{}" for keyword argument subtract_offset".'.format(
subtract_offset
)
)
# generate pulses
drag_wave = gauss_env + 1j * deriv_gauss_env
# Apply phase rotation
rot_drag_wave = rotate_wave(drag_wave, phase=phase)
return rot_drag_wave
[docs]
def sudden_net_zero(
t: np.ndarray,
amp_A: float,
amp_B: float,
net_zero_A_scale: float,
t_pulse: float,
t_phi: float,
t_integral_correction: float,
):
"""
Generates the sudden net zero waveform from :cite:t:`negirneac_high_fidelity_2021`.
The waveform consists of a square pulse with a duration of half
``t_pulse`` and an amplitude of ``amp_A``, followed by an idling period (0
V) with duration ``t_phi``, followed again by a square pulse with amplitude
``-amp_A * net_zero_A_scale`` and a duration of half ``t_pulse``, followed
by a integral correction period with duration ``t_integral_correction``.
The last sample of the first pulse has amplitude ``amp_A * amp_B``. The
first sample of the second pulse has amplitude ``-amp_A * net_zero_A_scale *
amp_B``.
The amplitude of the integral correction period is such that ``sum(waveform)
== 0``.
If the total duration of the pulse parts is less than the duration set by
the ``t`` array, the remaining samples will be set to 0 V.
The various pulse part durations are rounded **down** (floor) to the sample
rate of the ``t`` array. Since ``t_pulse`` is the total duration of the two
square pulses, half this duration is rounded to the sample rate. For
example:
.. jupyter-execute::
import numpy as np
from quantify_scheduler.waveforms import sudden_net_zero
t = np.linspace(0, 9e-9, 10) # 1 GSa/s
amp_A = 1.0
amp_B = 0.5
net_zero_A_scale = 0.8
t_pulse = 5.0e-9 # will be rounded to 2 pulses of 2 ns
t_phi = 2.6e-9 # rounded to 2 ns
t_integral_correction = 4.4e-9 # rounded to 4 ns
sudden_net_zero(
t, amp_A, amp_B, net_zero_A_scale, t_pulse, t_phi, t_integral_correction
)
Parameters
----------
t
A uniformly sampled array of times at which to evaluate the function.
amp_A
Amplitude of the main square pulse
amp_B
Scaling correction for the final sample of the first square and first sample
of the second square pulse.
net_zero_A_scale
Amplitude scaling correction factor of the negative arm of the net-zero pulse.
t_pulse
The total duration of the two half square pulses. The duration of each
half is rounded to the sample rate of the ``t`` array.
t_phi
The idling duration between the two half pulses. The duration is rounded
to the sample rate of the ``t`` array.
t_integral_correction
The duration in which any non-zero pulse amplitude needs to be
corrected. The duration is rounded to the sample rate of the ``t`` array.
"""
sampling_rate = t[1] - t[0]
single_arm_samples = int(t_pulse / 2 / sampling_rate)
mid_samples = int(t_phi / sampling_rate)
num_corr_samples = int(t_integral_correction / sampling_rate)
if 2 * single_arm_samples + mid_samples + num_corr_samples > len(t):
raise ValueError(
"Specified pulse part durations add up to longer than the given time array."
)
waveform = np.zeros(len(t))
waveform[:single_arm_samples] = amp_A
waveform[single_arm_samples - 1] = amp_A * amp_B
waveform[
single_arm_samples + mid_samples : 2 * single_arm_samples + mid_samples
] = (-amp_A * net_zero_A_scale)
waveform[single_arm_samples + mid_samples] = -amp_A * net_zero_A_scale * amp_B
integral_value = -sum(waveform) / num_corr_samples
waveform[
2 * single_arm_samples
+ mid_samples : 2 * single_arm_samples
+ mid_samples
+ num_corr_samples
] = integral_value
return waveform
# ----------------------------------
# Utility functions
# ----------------------------------
[docs]
def rotate_wave(wave: np.ndarray, phase: float) -> np.ndarray:
"""
Rotate a wave in the complex plane.
Parameters
----------
wave
Complex waveform, real component corresponds to I, imaginary component to Q.
phase
Rotation angle in degrees.
Returns
-------
:
Rotated complex waveform.
"""
angle = np.deg2rad(phase)
rot = (np.cos(angle) + 1.0j * np.sin(angle)) * wave
return rot
[docs]
def skewed_hermite(
t: np.ndarray,
duration: float,
amplitude: float,
skewness: float,
phase: float,
pi2_pulse: bool = False,
center: Optional[float] = None,
duration_over_char_time: float = 6.0,
) -> np.ndarray:
"""
Generates a skewed hermite pulse for single qubit rotations in NV centers.
A Hermite pulse is a Gaussian multiplied by a second degree Hermite polynomial.
See :cite:t:`Beukers_MSc_2019`, Appendix A.2.
The skew parameter is a first order amplitude correction to the hermite pulse. It
increases the fidelity of the performed gates.
See :cite:t:`Beukers_MSc_2019`, section 4.2. To get a "standard" hermite
pulse, use ``skewness=0``.
The hermite factors are taken from equation 44 and 45 of
:cite:t:`Warren_NMR_pulse_shapes_1984`.
Parameters
----------
t
Times at which to evaluate the function.
duration
Duration of the pulse in seconds.
amplitude
Amplitude of the pulse.
skewness
Skewness in the frequency space
phase
Phase of the pulse in degrees.
pi2_pulse
if True, the pulse will be pi/2 otherwise pi pulse
center
Optional: time after which the pulse center occurs. If ``None``, it is
automatically set to duration/2.
duration_over_char_time
Ratio of the pulse duration and the characteristic time of the hermite
polynomial. Increasing this number will compress the pulse. By default, 6.
Returns
-------
:
complex skewed waveform
"""
# Hermite factors are taken from paper cited in docstring.
PI_HERMITE_FACTOR = 0.956
PI2_HERMITE_FACTOR = 0.667
# Determine parameters based on switches:
# - characteristic time of hermite polynomial
# - hermite factor
# - center position of pulse
t_hermite = duration / duration_over_char_time
hermite_factor = PI2_HERMITE_FACTOR if pi2_pulse else PI_HERMITE_FACTOR
if center is None:
center = duration / 2.0
# normalize time array for easier evaluation
center_total = center + t[0]
normalized_time = (t - center_total) / t_hermite
# Hermite pulse with zero skewness
h_t = (1 - hermite_factor * normalized_time**2) * np.exp(-(normalized_time**2))
# I and Q components
I = amplitude * h_t
Q = (
amplitude
* (skewness / np.pi)
* (normalized_time / t_hermite)
* (hermite_factor + 1 - hermite_factor * normalized_time**2)
* np.exp(-(normalized_time**2))
)
hermite = I + 1j * Q
# Rotate pulse to get correct phase
rotated_hermite = rotate_wave(hermite, phase)
return rotated_hermite
