PhD defence by Jesper Bjerge Christensen

Title: Tailored four-wave mixing for optical quantum information science



Principal supervisor: Prof. Karsten Rottwitt

Co-supervisor: Prof. Leif katsuo Oxenløwe



Evaluation Board

Assoc. Prof Niels Gregersen, DTU Fotonik

Lecturer Alberto Politi, University of Southampton, UK

Prof. Lars Magnus Ingemar Karlsson, University of Chalmers, Sweden


Master of the Ceremony





This thesis deals with applications of nonlinear four-wave mixing in the context of optical quantum information science. By enabling diverse functionalities such as single-photon generation, temporal shaping, and frequency conversion, four-wave mixing is a highly versatile tool for processing optical quantum information.

The first part addresses the use of spontaneous four-wave mixing for generating entangled photon pairs with the particular property that the photons are uncorrelated in time and frequency. Two schemes are proposed to achieve this. The first proposal relies on a gradually varying interaction between two orthogonally polarized pump pulses in a birefringent waveguide. It is shown that, if the two pump pulses undergo a complete walk-through, the two generated photons emerge in orthogonal polarizations with uncorrelated- and tailorable time-frequency distributions. The second proposal deals with photon-pair generation in a microring resonator. In this setting, it is shown that a dual-pulse configuration can be used to excite- and subsequently de-excite the resonator on a sub-lifetime timescale.  This turns out to strongly diminish time-frequency correlations. 

The second part considers the four-wave-mixing process Bragg scattering, which is known to enable noise-free frequency conversion. The Bragg-scattering process treated here, which occurs in a birefringent waveguide, is shown to allow for shape-preserving and strongly uni-directional conversion with a large acceptance bandwidth.


tor 13 dec 18
13:30 - 16:30


DTU Electro



Lyngby Campus build. 341, aud. 22