Fig. 4. Quantum measurements on a metasurface-based interferometer.

a Schematic view of the metasurface-based interferometer using a time delay τ between the two input photons. b Selected time delays τ illustrated at the HOM-dip measurement. c Experimental results for the two-photon state with three different time delays τ after passing through the MBI. The count rates at both detectors are independent of the introduced phase ϕ and the time delay τ. The measured coincidence rates show an oscillatory behavior with lower visibility at higher delaytimes. The obtained visibility values are 86.8 ± 1.1% for the case of no time delay, 67 ± 2% for $\tau =3.0\mathrm{ps}$ and 44 ± 5% for $\tau =17.7\mathrm{ps}$