A delayed choice experiment in quantum optics
Analyzing which path a particle takes in a two-slit system, or analogously through an interferometer, was traditionally described by the addition of a momentum kick to induce particle properties onto a quantum wave thereby destroying the interference pattern. One method of obtaining which-way information without introducing a momentum kick can be done through assigning distinguishable states through plane polarizations within a two arm system such as a Mach-Zehnder interferometer. After the photon leaves the interferometer, the which-way information can be erased using a quantum eraser which will restore the interference pattern. This experiment demonstrated that a polarizer set at an intermediate position erases the which-way information within a Mach-Zehnder interferometer thus acting as a quantum eraser.
* Indicates faculty mentor.