# cosine_pulse_pwc¶

The Boulder Opal Toolkits are currently in beta phase of development. Breaking changes may be introduced.

cosine_pulse_pwc(duration, segment_count, amplitude, drag=None, start_time=0.0, end_time=None, flat_duration=None, *, name=None)

Create a Pwc representing a cosine pulse.

Parameters
• duration (float) – The duration of the signal, $$T$$.

• segment_count (int) – The number of segments in the PWC. Must be at least six.

• amplitude (float or complex or Tensor) – The amplitude of the pulse, $$A$$. It must either be a scalar or contain a single element.

• drag (float or Tensor, optional) – The DRAG parameter, $$\beta$$. If passed, it must either be a scalar or contain a single element. Defaults to no DRAG correction.

• start_time (float, optional) – The time at which the cosine pulse starts, $$t_\mathrm{start}$$. Defaults to 0.

• end_time (float, optional) – The time at which the cosine pulse ends, $$t_\mathrm{end}$$. Defaults to the given duration $$T$$.

• flat_duration (float, optional) – The amount of time to remain constant after the peak of the cosine, $$t_\mathrm{flat}$$. If passed, it must be positive and less than the difference between end_time and start_time. Defaults to None, in which case no constant part is added to the cosine pulse.

• name (str, optional) – The name of the node.

Returns

The sampled cosine pulse. If no flat duration is passed then the pulse is evenly sampled between $$0$$ and $$T$$. If one is passed, the flat part of the pulse is described by one or two segments (depending on the value of segment_count), and the rest of the pulse is sampled with the remaining segments.

Return type

Pwc

pulses.cosine_pulse()

Function to create a Pulse object representing a cosine pulse.

pulses.gaussian_pulse_pwc()

Create a Pwc representing a Gaussian pulse.

pulses.hann_series_pwc()

Create a Pwc representing a sum of Hann window functions.

pulses.sech_pulse_pwc()

Create a Pwc representing a hyperbolic secant pulse.

pulses.sinusoid_pwc()

Create a Pwc representing a sinusoidal oscillation.

pulses.square_pulse_pwc()

Create a Pwc representing a square pulse.

cos()

Calculate the element-wise cosine of an object.

Notes

The cosine pulse is defined as

$\begin{split}\mathop{\mathrm{Cos}}(t) = \begin{cases} 0 &\mathrm{if} \quad t < t_\mathrm{start} \\ \frac{A}{2} \left[1+\cos \left(\omega \{t-\tau_-\} \right) + i\omega\beta \sin \left(\omega \{t-\tau_-\}\right)\right] &\mathrm{if} \quad t_\mathrm{start} \le t < \tau_- \\ A &\mathrm{if} \quad \tau_- \le t \le \tau_+ \\ \frac{A}{2} \left[1+\cos \left(\omega\{t-\tau_+\}\right) + i\omega \beta\sin \left(\omega \{t-\tau_+\}\right)\right] &\mathrm{if} \quad \tau_+ < t \le t_\mathrm{end} \\ 0 &\mathrm{if} \quad t > t_\mathrm{end} \\ \end{cases},\end{split}$

where $$\omega=2\pi /(t_\mathrm{end}-t_\mathrm{start} - t_\mathrm{flat})$$, $$\tau_\mp$$ are the start/end times of the flat segment, with $$\tau_\mp=(t_\mathrm{start}+t_\mathrm{end} \mp t_\mathrm{flat})/2$$.

If the flat duration is zero (the default setting), this reduces to

$\mathop{\mathrm{Cos}}(t) = \frac{A}{2} \left[1+\cos \left(\omega \{t-\tau\} \right) + i\omega\beta \sin \left(\omega \{t-\tau\}\right)\right] \theta(t-t_\mathrm{start}) \theta(t_\mathrm{end}-t),$

where now $$\omega=2\pi /(t_\mathrm{end}-t_\mathrm{start})$$, $$\tau=(t_\mathrm{start}+t_\mathrm{end})/2$$ and $$\theta(t)$$ is the Heaviside step function.

Examples

Define a cosine PWC pulse.

>>> graph.pulses.cosine_pulse_pwc(
...     duration=3.0, segment_count=100, amplitude=1.0, name="cos_pulse"
... )
<Pwc: name="cos_pulse", operation_name="time_concatenate_pwc", value_shape=(), batch_shape=()>
>>> result = qctrl.functions.calculate_graph(graph=graph, output_node_names=["cos_pulse"])
>>> result.output["cos_pulse"]
[
{'duration': 0.03, 'value': 0.00024},
{'duration': 0.03, 'value': 0.00221},
...
{'duration': 0.03, 'value': 0.00221},
{'duration': 0.03, 'value': 0.00024}
]


Define a flat-top cosine PWC pulse with a DRAG correction.

>>> graph.pulses.cosine_pulse_pwc(
...     duration=3.0,
...     segment_count=100,
...     amplitude=1.0,
...     drag=0.1,
...     start_time=1.0,
...     end_time=2.0,
...     flat_duration=0.3,
...     name="cos_flat",
... )
<Pwc: name="cos_flat", operation_name="time_concatenate_pwc", value_shape=(), batch_shape=()>
>>> result = qctrl.functions.calculate_graph(graph=graph, output_node_names=["cos_flat"])
>>> result.output["cos_flat"]
[
{'duration': 1.0, 'value': 0j},
{'duration': 0.0072, 'value': (0.0002-0.0146j)}
...
{'duration': 0.0072, 'value': (0.0002+0.0146j)},
{'duration': 1.0, 'value': 0j}
]


Define a cosine pulse with optimizable parameters.

>>> amplitude = graph.optimization_variable(
...     count=1, lower_bound=0, upper_bound=2.*np.pi, name="amplitude"
... )
>>> drag = graph.optimization_variable(
...     count=1, lower_bound=0, upper_bound=1., name="drag"
... )
>>> graph.pulses.cosine_pulse_pwc(
...     duration=3.0,
...     segment_count=100,
...     amplitude=amplitude,
...     drag=drag,
...     name="cos_pulse",
... )
<Pwc: name="cos_pulse", operation_name="time_concatenate_pwc", value_shape=(), batch_shape=()>