fft

performs the fourier transformation of a signal without the lot of the usual hassle that is involved

Contents

Syntax

fft(y)

Description

fft(y) Returns the fourier transformed of the vector y. The frist entry of this vector corresponds to the frequency content for $\omega =0$. The System class manages a frequency vector that corresponds to the generated data. Using the setdf(df) method the resolution of the fouriertransform can be adjusted. Trailing zeros are automatically attached to y.

Example

clear; close all;
s = System;
s.addEntity(Nlevel(1),'qbit');
s.addEntity(Qoscillator(3,1),'cavity');
s.addCoupling('qbit','cavity',0.05);
s.addDissipation('qbit',40);
s.addDissipation('cavity',40);
s.addExternalField(Gausspulse(0.04,50,15,1),'qbit'); %external laser pulse excites the system
s.setTimestep(0.1);
s.simulate();

s.setdf(0.0001);
plot(2*pi*s.f,abs(s.fft(s.getPolarisation('qbit'))));
axis([0.8 1.2 -inf inf]);
xlabel('Frequency');
ylabel('abs(fft(Polarisation))');
title('Qbit Coupled to a cavity');