fits.py 文件源码

def fit_photon_number(xdata, ydata, params):
    ''' Fit number of measurement photons before a Ramsey. See McClure et al., Phys. Rev. App. 2016
    input params:
    1 - cavity decay rate kappa (MHz)
    2 - detuning Delta (MHz)
    3 - dispersive shift 2Chi (MHz)
    4 - Ramsey decay time T2* (us)
    5 - exp(-t_meas/T1) (us), only if starting from |1> (to include relaxation during the 1st msm't)
    6 - initial qubit state (0/1)
    '''
    params = [2*np.pi*p for p in params[:3]] + params[3:] # convert to angular frequencies
    def model_0(t, pa, pb):
        return (-np.imag(np.exp(-(1/params[3]+params[1]*1j)*t + (pa-pb*params[2]*(1-np.exp(-((params[0] + params[2]*1j)*t)))/(params[0]+params[2]*1j))*1j)))
    def model(t, pa, pb):
        return  params[4]*model_0(t, pa, pb) + (1-params[4])*model_0(t, pa+np.pi, pb) if params[5] == 1  else model_0(t, pa, pb)
    popt, pcov = curve_fit(model, xdata, ydata, p0 = [0, 1])
    perr = np.sqrt(np.diag(pcov))
    finer_delays = np.linspace(np.min(xdata), np.max(xdata), 4*len(xdata))
    fit_curve = model(finer_delays, *popt)
    return popt[1], perr[1], (finer_delays, fit_curve)