Effective coherence times due to multiple noise channels

In the case of multiple noise channels inducing qubit depolarization, the effective (total) depolarization time follows from the addition of the individual rates,

\[\frac{1}{T_{1}^{\rm eff}} = \sum_k \frac{1}{T_{1}^{k}},\]

where the sum runs over all included noise channels.

An analogous statement holds for the effective dephasing time, which includes contributions from both pure dephasing as well as depolarization channels. This total \(T_{2}\) time is defined as

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

where \(k\) (\(j\)) runs over all relevant pure-dephasing (depolarization) channels.

scqubits enables the evaluation of these effective coherence times. By default, the noise channels that are included in the calculation, can be shown using the effective_noise_channels method for each qubit. Note that this list may not include all the noise channels that can actually be calculated for any given qubit, to see a list of those, the supported_noise_channels method could be used. Users can also explicitly specify what noise processes should be included in effective noise calculations.

Calculating \(T_1\) and \(T_2\) can be done via a methods t1_effective and t2_effective respectively.

For more information on the method signatures, see the API documentation to see the complete list.