# qml.devices.default_gaussian.photon_number¶

photon_number(cov, mu, params, hbar=2.0)[source]

Calculates the mean photon number for a given one-mode state.

Parameters
• cov (array) – $$2\times 2$$ covariance matrix

• mu (array) – length-2 vector of means

• params (None) – no parameters are used for this expectation value

• hbar (float) – (default 2) the value of $$\hbar$$ in the commutation relation $$[\x,\p]=i\hbar$$

Returns

contains the photon number expectation and variance

Return type

tuple