Research  


A. Quantum Information Processing with Photons and Spins

 

  (From left to right, front row: David, Kai-Mei, Eleni, Susan, Katsuya; second row: Young Chul, Stephan, Chia-Yu, Bingyang, Shin’ichi, Yoshi, Third row: Kaoru, Neil, Thaddeus, Kristiaan, Hiroki)

 

Semiconductor systems provide robust and high-speed single-photon sources and single-photon detectors at wide wavelength range from visible to near infrared. A series of experiment have been performed in our group to generate single photons using a single semiconductor quantum-dot (QD) in micro-cavities and also single-photon detectors using periodically-poled Lithium Niobate (PPLN) and silicon avalanche photodiodes. These components are the key building-blocks for the applications of quantum key distribution and quantum repeaters. One of the hottest topics in our group is the donor-bound exciton system in GaAs substrate. A Zeeman sub-levels of a bound electron spin state in the system provide metastable ground states, together with a lowest bound exciton state, forms a so-called three-level lambda system. The first coherent population transformation has been performed via coherent Raman process with a solid-state semiconductor system.

 

          1. Single Photon and Entangled-pair Source

          2. Single Photon Detector

          3. Quantum Key Distribution

          4. Coherent control in Semiconductors

          5. Quantum Repeater

          6. Nuclear Memory

          7. Quantum Computer Architecture

                                                                                                                                     

 

B. Quantum Many-Body Systems and Quantum Simulation

 

(From left to right, front row: Hui, Neil, Yoshi, Na Young; second row: George, Shoko, Shinichi; last Row: Tim, David, Patrik, Cyrus, Fumiko)

 

Quantum mechanics is a successful framework to describe statics and dynamics of individual and ensembles of constituting particles at the atomic and subatomic levels. It provides microscopic understanding of phenomena in nature by establishing Hamiltonian of the system and finding out the ground state properties. It becomes unavoidable to encounter the system ground state including interactions amongst participating entities; however it is a daunting and impossible task to handle all degrees of freedom with enormous numbers of particles exactly. Quantum statistics plays a crucial role to make a conjunction between macroscopic thermodynamic properties and microscopic quantities by treating effectively many-body interaction.

 

Here we examine various systems to observe quantum phase transition in the ground states arising from fundamental correlations innate in systems via experimental probes and theoretical tools. In particular, quantum simulation is a distinct approach to perceive unresolved quantum phenomena since its underlying philosophy lies on the fact that building  quantum system which emulate other quantum systems not only in solid state systems but also in atomic physics, quantum optics, quantum chemistry and so on. This area will provide new insights to assess interesting questions existent in nature.

 

1. Quantum Statistics in Two-Dimensional Electron Gas Systems

2. Exciton Polariton Bose-Einstein Condensation

3. Tomonaga-Luttinger Liquid in Carbon Nanotubes

4. Quantum Simulation of Hubbard Models

5. Quantum Simulation of Lattice Gauge Models

6. Quantum Simulation of Spin Models

 

 

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                  Last Update: N. Y. Kim on Sep. 21, 2009