# Estimation of pulsed driven qubit parameters via quantum Fisher information

## TL;DR

This paper investigates how different pulse shapes affect the precision of estimating initial parameters of a qubit using quantum Fisher information, revealing conditions for optimal parameter estimation.

## Contribution

It introduces a comparative analysis of pulse shapes on qubit parameter estimation using quantum Fisher information, highlighting conditions for high-precision measurement.

## Key findings

- Rectangular pulses allow increased estimation of weight parameter with specific detuning and pulse strength.
- Maximum Fisher information for phase estimation occurs at resonance when initial phase is π/2.
- Exponential and sin^2 pulses enable high-precision estimation of both parameters regardless of detuning.

## Abstract

We estimate the initial weight and phase parameters ($\theta, \phi)$ of a single qubit system initially prepared in the coherent state $\ket{\theta,\phi}$ and interacts with three different shape of pulses; rectangular, exponential, and $sin^2$-pulses. In general, we show that the estimation degree of the weight parameter depends on the pulse shape and the initial phase angle, $(\phi)$. For the rectangular pulse case, increasing the estimating rate of the weight parameter via the Fisher information function $(\mathcal{F}_\theta)$ is possible with small values of the atomic detuning parameter and larger values of the pulse strength. Fisher information $(\mathcal{F}_\phi)$ increases suddenly at resonant case to reach its maximum value if the initial phase $\phi=\pi/2$ and consequently one may estimate the phase parameter with high degree of precision. If the initial system is coded with classical information, the upper bounds of Fisher information for resonant and non-resonant cases are much larger and consequently one may estimate the pahse parameter with high degree of estimation. Similarly as the detuning increases the Fisher information decreases and therefore the possibility of estimating the phase parameter decreases. For exponential, and $sin^2$-pulses the Fisher information is maximum ($\mathcal{F}_{\theta,\phi}=1$) and consequently one can always estimate the weight and the phase parameters $(\theta,\phi)$ with high degree of precision.