Ph.D Thesis

Ph.D StudentAkopian Nikolay
SubjectCorrelated and Entangled Pairs of Single
Photons from Semiconductor Quantum Dots
DepartmentDepartment of Physics
Supervisors PROFESSOR EMERITUS David Gershoni
Full Thesis textFull thesis text - English Version


Entangled photons are attractive carriers of quantum information. Once produced, they can be easily manipulated and travel long distances unaffected. Most experiments in quantum information have used spontaneous parametric down-conversion, which produces a random number of entangled photon pairs. However quantum information technology requires non-random, or “event ready”, entangled photons.

     Semiconductor quantum dots are perfect candidates for sources of such “event ready” entangled photons. They are reliable sources of single photons on demand and they are compatible with modern quantum information technology.

     This work focuses on demonstrating generation of polarization-entangled photons from a single semiconductor quantum dot. A neutral quantum dot can contain two electron-hole pairs in its ground state. Their sequential radiative recombination will produce a pair of photons. Here we demonstrate for the first time that the polarization state of such pairs of photons becomes entangled when spectral filtering is applied. The measured density matrix of the photon pair satisfies the Peres criterion for entanglement and violates Bell's inequality. We show that the spectral filtering erases the “which path” information contained in the photons color and that the remnant information in the quantum dot degrees of freedom is negligible. Moreover, by applying additional temporal window, quantum dot becomes a physical source of entangled light.