Super-stable tomography of any linear optical device

Understand

Linear optical circuits of growing complexity are playing an increasing role in emerging photonic quantum technologies.

• Individual photonic devices are typically described by a unitary matrix containing amplitude and phase information, the characterisation of which is a key task.
• We present a constructive scheme to retrieve the unitary matrix describing an arbitrary linear optical device using data obtained from one-photon and two-photon ensembles.
• The scheme is stable on the arbitrarily increasable length scale of the photon packet and independent of photon loss at input and output ports of the device.