Reconfigurable integrated photonic device to test Born’s rule

Born’s rule claims that quantum interference occurs only between pairs of paths. Any deviation from this rule can be measured through multi-arm interferometers. For this reason, utilizing the femtosecond laser micromachining technique, we realize a reconfigurable integrated three-path interferometer in which, by means of optical switches, we can close or open the optical path at will, so that all interference contributions can be measured individually. We measured the normalized contribution of the third-order interference term, quantified by the Sorkin’s parameter observing a result of k = −4.677 × 10⁻⁴ with a standard deviation of kstd = 8.394 × 10⁻⁴ . To increase the sensitivity of this measurement, single photons can be used to suppress errors caused by the nonlinearity of the detectors.