Quantum non demolition parity measurements of itinerant microwave fields

Capitalizing on recent demonstrations of quantum non demolition (QND) detection of individual itinerant microwave photons [1,2] we demonstrate parity measurements applied to input fields with photon number up to ten.

Defining a mode to be characterized by the temporal shape of a displacement field added onto it, we recover its Wigner function without making use of reconstruction or maximum likelihood methods. We present results of this phase space tomography method for propagating fields for various classical and quantum input fields.

The non demolition character of the measurement also allows for heralding highly non-classical states of light, such as multi-photon cat states, which are relevant for quantum information processing.

[1] Kono et al., Nat. Phys 14, 546-549 (2018)
[2] Besse et al., PRX 8, 021003 (2018)