Lahore University of Management Sciences

LUMS to Feature a Talk on DreSBASSEd State's Emissions

April 26, 2012

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The Department of Physics at LUMS brings a talk on:

Dressed State's Emission from Single Quantum Dots


Dr. Ata Ul Haq

Date: Thursday, April 26, 2012
Time: 02:00 p.m. - 03:00 p.m.
Venue: SBASSE Building 2nd floor 9-2C1 (Physics Computational Lab)


Implementation of quantum computation schemes heavily rely on the generation of highly coherent non-classical light. Semiconductor-based quantum light sources gain special importance in this context as they can be monolithically integrated using advanced IC technology. Semiconductor structures like Quantum Dots (QDs) can be used as quantum light emitters which can possibly be integrated in future quantum computational circuits as generator of 'flying qubits'.

These 'flying qubits' can have different forms like single-, entangled- and cascaded- or even heralded-photons each of which has significance for quantum logic circuits. Single quantum dots over the last decade have shown excellent optical properties and all these different quantum states of light have been demonstrated. But most of these schemes rely on non-resonant excitation schemes which exhibit particularly high dephasing in the emission and thus are unsuitable for applications. In this work, we demonstrate single- and cascaded-two photon emission from a resonantly excited single quantum dot. We make use of the highly non-linear regime of a resonantly driven two-level system, usually described by 'dressed' states, to realize these sources with highly coherent emission properties.

Most of these effects have already been demonstrated using isolated atoms but our measurements exhibit distinct deviations from the usual atom-photon interaction models. Since semiconductor QD is a solid state system, we observe solid-state-specific dephasing mechanisms in such single quantum emitters. In particular, we show that electron-phonon coupling in these systems can be used as a resource in the cavity quantum electrodynamics regime, where a single QD is embedded in a high-Q microcavity.

About the Speaker

Ata Ulhaq completed his bachelors studies in engineering sciences from G. I. K. Institute in 2003. Afterwards he joined University of Stuttgart for a Masters in Physics. He worked at Max Planck Institute for Solid State Research in Stuttgart on developing precise emission tuning techniques of single quantum dots and optical microacvities. Later he spent time at Hamburg University as a research scholar on surface plasmons and metamaterials. He then joined G. I. K. Institute as a research associate for one year. In 2008, he was awarded the International Max Planck Research scholarship for developing highly coherent single- and cascaded-photon sources using semiconductor quantum dots. He also worked on cavity quantum electrodynamics effects in these structures and studied the solid-stat specific effects in such quantum emitters. Recently he finished his PhD diSBASSErtation at the University of Stuttgart.