Measurement and control of spatial qubits generated by passing photons through double-slits

TL;DR

This paper experimentally investigates the entanglement and measurement techniques of spatial qubits created by passing photons through double slits, demonstrating a method to access the full quantum state in a single measurement plane.

Contribution

It introduces a novel measurement approach that captures complete spatial qubit information in a single plane, facilitating quantum tomography and potential applications in quantum information.

Findings

Confirmed entanglement via quantum tomography.

Demonstrated measurement of complete Hilbert space in a single plane.

Showed extension potential to multi-dimensional systems.

Abstract

We present an experimental study of the non-classical correlations of a pair of spatial qubits formed by passing two down-converted photons through a pair of double slits. After confirming the entanglement generated in our setup by quantum tomography using separate measurements of the slit images and the interference patterns, we show that the complete Hilbert space of the spatial qubits can be accessed by measurements performed in a single plane between the image plane and the focal plane of a lens. Specifically, it is possible to obtain both the which-path and the interference information needed for quantum tomography in a single scan of the transversal distribution of photon coincidences. Since this method can easily be extended to multi-dimensional systems, it may be a valuable tool in the application of spatial qudits to quantum information processes.