Propagation of spatially entangled qudits through free space

Abstract

We show the propagation of entangled states of high-dimensional quantum systems. The qudits states were generated using the transverse correlation of the twin photons produced by spontaneous parametric down-conversion. Their free-space distribution was performed at the laboratory scale and the propagated states maintained a high-fidelity with their original form. The use of entangled qudits allow an increase in the quantity of information that can be transmitted and may also guarantee more privacy for communicating parties. Therefore, studies about propagating entangled states of qudits are important for the effort of building quantum communication networks.Comment: 5 Pages, 4 Figures, REVTeX

Spatial correlations in parametric down-conversion

“…Free-space distribution of polarization entangled qubits through the atmosphere was demonstrated for a distance of 144km [271]. The experimental free-space propagation of two entangled four-dimensional qudits or "ququarts" produced by four-slit apertures was reported in reference [272]. Free space propagation of the entangled photons was performed on a laboratory scale.…”

Experimental simulation of decoherence in photonics qudits

“…A 300 mm focal length lens placed 50 mm before the crystal is used for focusing the pump beam at the multi-slit array plane. When the beam waist at this plane is smaller than the separation between the slits, the spatial part of the two-photon state after crossing the aperture will be given by 21 29 40 41 42 43 44 45 …”

Fast entanglement detection for unknown states of two spatial qutrits

“…This is done by changing the gray level of the LCD2, independently, at these points. At the plane of image formation, the diffracted photon is again described by Eq (3) [48] and, therefore, the modulation being done by the second SLM allows for the modification of the imaginary parts of the spatial qutrits states. After the reflection on this SLM, the light is collimated and focused by a set of lenses (L2 and L3) at the detection plane, where a pointlike detector (APD) is used to record the single photons at the center of the interference patterns formed.…”