Measurement-Dependent Erasure of Distinguishability for the Observation of Interference in an Unbalanced SU(1,1) Interferometer

Abstract

It is known that quantum interference can disappear with the mere possibility of distinguishability without actually performing the act but can be restored by erasing the path information. A common erasure method is by conditional projective measurement known as a “quantum eraser.” On the other hand, the essence of quantum interference is amplitude addition. So, direct amplitude measurement and subsequent addition can also lead to the recovery of interference. In this paper, we create temporal distinguishability in an unbalanced SU(1,1) interferometer and observe no interference in the direct photodetection of the outputs. Different from the quantum eraser scheme, we recover interference via amplitude measurement by homodyne detection even with distinguishability in photon generation but no conditional projective measurement. The new mechanism of recovering interference can be applied to other unbalanced interferometers and should have practical applications in quantum metrology and sensing.