Of Einstein and entanglement: Quantum erasure deconstructs wave-particle duality

Quantum physics presents several counterintuitive features, including entanglement, tunneling and – as demonstrated in double-slit experiments – wave-particle duality. When studying wave-particle duality, however, so-called interferometric quantum eraser experiments – in which wave-like behavior can be restored by erasing path information – allow researchers to perform differential measurements on each of two entangled quantum systems. (Double-slit experiments not involving quantum erasure utilize superposition of single particles, while in quantum eraser experiments two particles are entangled.) Specifically, the particle feature's welcher-weg (which-path) information is erased (or not) from one system, and interference-based measurements in the other system are used to observe (or not, as the case may be) its wave feature.