---
title: Sech (v1.1)
description: API reference for qiskit.pulse.library.Sech in qiskit v1.1
source: https://eu-de.quantum.cloud.ibm.com/docs/en/api/qiskit/1.1/qiskit.pulse.library.Sech_fun.rst
---

# qiskit.pulse.library.Sech

`qiskit.pulse.library.Sech(duration, amp, sigma, angle=0.0, name=None, zero_ends=True, limit_amplitude=None)`

[GitHub](https://github.com/Qiskit/qiskit/tree/stable/1.1/qiskit/pulse/library/symbolic_pulses.py#L1826-L1899)

An unnormalized sech pulse.

The sech function is centered around the halfway point of the pulse, and the envelope of the pulse is given by:

$$
f(x) = \text{A}\text{sech}\left(
\frac{x-\mu}{\text{sigma}}\right)  ,  0 <= x < duration
$$

where $\text{A} = \text{amp} \times\exp\left(i\times\text{angle}\right)$, and $\mu=\text{duration}/2$.

If zero\_ends is set to True, the output y is modified: .. math:

```python
y\left(x\right) \mapsto \text{A}\frac{y-y^{*}}{\text{A}-y^{*}},
```

where $y^{*}$ is the value of $y$ at the endpoints (at $x=-1 and :math:`x=\text{duration}+1$). This shifts the endpoints value to zero, while also rescaling to preserve the amplitude at :math:text\{duration}/2\`\`.

**Parameters**

- **duration** ([*int*](https://docs.python.org/3/library/functions.html#int) *| ParameterValueType*) – Pulse length in terms of the sampling period dt.
- **amp** ([*float*](https://docs.python.org/3/library/functions.html#float)  *|*[*ParameterExpression*](/docs/api/qiskit/1.1/qiskit.circuit.ParameterExpression "qiskit.circuit.ParameterExpression")) – The magnitude of the amplitude of the pulse (the value at the midpoint duration/2).
- **sigma** ([*float*](https://docs.python.org/3/library/functions.html#float)  *|*[*ParameterExpression*](/docs/api/qiskit/1.1/qiskit.circuit.ParameterExpression "qiskit.circuit.ParameterExpression")) – A measure of how wide or narrow the sech peak is in terms of dt; described mathematically in the class docstring.
- **angle** ([*float*](https://docs.python.org/3/library/functions.html#float)  *|*[*ParameterExpression*](/docs/api/qiskit/1.1/qiskit.circuit.ParameterExpression "qiskit.circuit.ParameterExpression") *| None*) – The angle in radians of the complex phase factor uniformly scaling the pulse. Default value 0.
- **name** ([*str*](https://docs.python.org/3/library/stdtypes.html#str) *| None*) – Display name for this pulse envelope.
- **zero\_ends** ([*bool*](https://docs.python.org/3/library/functions.html#bool) *| None*) – If True, zeros the ends at x = -1, x = duration + 1, but rescales to preserve amp. Default value True.
- **limit\_amplitude** ([*bool*](https://docs.python.org/3/library/functions.html#bool) *| None*) – If `True`, then limit the amplitude of the waveform to 1. The default is `True` and the amplitude is constrained to 1.

**Returns**

ScalableSymbolicPulse instance.

**Return type**

ScalableSymbolicPulse