NIRT: Semiconductor nanostructures and photonic crystal microcavities for quantum information processing at terahertz frequencies M. S. Sherwin and P. Petroff, UC Santa Barbara, Craig Pryor, University of Iowa, and J. Vuckovic, Stanford University, CCF We have fabricated, characterized, and calculated the quantum states of self-assembled cylindrical “quantum posts,” a new type of semiconductor nanostructure. Quantum posts have precisely- controllable heights which can be more than an order of magnitude greater than the heights of conventional self-assembled InGaAs quantum dots. The photoluminescence spectrum of a single 23 nm high quantum post is shown as a function of electric field applied along the growth direction (axis of the post). The red dashed line follows one of the peaks, exhibiting a very steep, linear red-shift with increasing electric field. This red-shift occurs as the electron and hole are attracted to opposite ends of the quantum post. The slope of the line increases with quantum post length, and can be used to measure the effective length of a post. J. He et al., Nano Lett. 7, 802 (2007) H. Krenner Physica E, in press Quantum posts: Transmission electron micrographs of 23 nm high (top left) and 40 nm (top right) quantum posts. Bottom: interband photoluminescence spectrum vs. electric field (note electric field increases moving right to left)

Scientific and technological impact: The development and control of quantum posts opens new doors for quantum information processing and terahertz science and technology. Making robust, three-D quantum confined structures with transitions at terahertz frequencies is highly desirable for emitters, detectors, and other applications. An electron trapped in a 40 nm long quantum post is expected to have a 1st- excited to ground state transition near 1.7 THz (6.5 meV--see figure at right) with long lifetimes. With their relatively large volumes, quantum posts embedded in suitably designed microcavities tuned to a near-ir or terahertz resonance offer enhanced likelihood of strongly coupling the cavity mode with the quantum states of the quantum post, a necessary step for many applications in quantum information processing. Educational Impact: One elementary school science teacher, five undergraduates, 10 graduate students, and two post-doctoral researchers have been involved with activities sponsored by this grant. The teacher, two undergrads and one grad. students have developed two hands-on educational modules which are leant to elementary school teachers and cover all of the California state standards for 4th-graders in the area of circuits and electricity and magnetism. NIRT: Semiconductor nanostructures and photonic crystal microcavities for quantum information processing at terahertz frequencies M. S. Sherwin and P. Petroff, UC Santa Barbara, Craig Pryor, University of Iowa, and J. Vuckovic, Stanford University, CCF E (meV)   Thz Nanostructures for THz: Wave functions and lowest two electronic energy levels computed for a 40 nm high quantum post using 8-band k.p theory (C. Pryor).