Generation and characterization of spectrally factorable biphotons
Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science.
Franco N.C. Wong.
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Spectrally unentangled biphotons with high single-spatiotemporal-mode purity are highly desirable for many quantum information processing tasks. We generate biphotons with an inferred heralded-state spectral purity of 99%, the highest to date without any spectral filtering, by pulsed spontaneous parametric down-conversion (SPDC) in a custom-fabricated periodically-poled KTiOPO₄ (PPKTP) crystal under extended Gaussian phase-matching conditions. The high purity achieved is made possible by the Gaussian phase-matching function of our custom PPKTP crystal. Without applying spectral filtering and using a standard PPKTP crystal, the highest previously reported purity is 93%. We characterize the joint spectral density of the generated biphoton by converting the spectral content to temporal information via dispersion through a 42-km SMF28 fiber. To characterize the JSD at high spectral resolution and more eciently, we employ a commercially available dispersion compensation module (DCM) with a dispersion equivalent to 100km of standard optical fiber and with an insertion loss of only 2.8 dB. Compared with the typical method of using two temperature-stabilized equal-length fibers that incurs an insertion loss of 20 dB per fiber, the DCM approach achieves high spectral resolution in a much shorter measurement time. We also verify the indistinguishability of the SPDC signal and idler photons via Hong-Ou-Mandel interferometric measurements. The near perfect interference visibility confirms that they are indeed indistinguishable.
Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2017.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 73-77).
DepartmentMassachusetts Institute of Technology. Department of Electrical Engineering and Computer Science.
Massachusetts Institute of Technology
Electrical Engineering and Computer Science.