scqubits.TunableTransmon.t2_effective#

TunableTransmon.t2_effective(noise_channels=None, common_noise_options=None, esys=None, get_rate=False)#

Calculate the effective \(T_2\) time (or rate).

The effective \(T_2\) is calculated by considering a variety of pure dephasing and depolarizing noise channels, according to the formula:

\[\frac{1}{T_{2}^{\rm eff}} = \sum_k \frac{1}{T_{\phi}^{k}} + \frac{1}{2} \sum_j \frac{1}{T_{1}^{j}},\]

where \(k\) (\(j\)) run over the relevant pure dephasing ( depolarization) channels that can contribute to the effective noise. By default all the noise channels given by the method effective_noise_channels are included. Users can also provide specific noise channels, with selected options, to be included in the effective \(T_2\) calculation. For example, assuming qubit is a qubit object, can can execute:

qubit.t2_effective(noise_channels=['t1_flux_bias_line', 't1_capacitive',
                                   ('tphi_1_over_f_flux', dict(A_noise=3e-6))],
                   common_noise_options=dict(T=0.050))
Parameters:

  • noise_channels (None or str or list(str) or list(tuple(str, dict))) – channels to be plotted, if None then noise channels given by supported_noise_channels are used

  • common_noise_options (dict) – common options used when calculating coherence times

  • esys (tuple(evals, evecs)) – spectral data used during noise calculations

  • get_rate (bool) – get rate or time

Returns:

time or rate – decoherence time in units of \(2\pi ({\rm system\,\,units})\), or rate in inverse units.

Return type:

float