title: Ultrafast Ramsey interferometry to implement cold atomic qubit gates.
abstract: Quantum computing is based on unitary operations in a two-level quantum system, a qubit, as the fundamental building block, and the ability to perform qubit operations in an amount of time that is considerably shorter than the coherence time is an essential requirement for quantum computation. Here, we present an experimental demonstration of arbitrary single-qubit SU(2) quantum gate operations achieved at a terahertz clock speed. Implemented by coherent control methods of tailored ultrafast laser interaction with cold rubidium atomic qubits, Bloch vector manipulation about all three rotational axes was successfully demonstrated. The dynamic evolution of the qubits was successfully measured by devised femtosecond Ramsey interferometry. We anticipate this demonstration to be a starting point to process quantum algorithm in a simplified manner by a programmed sequence of femtosecond laser pulses.
authors: 1] Department of Physics, KAIST, Daejeon 305-701, Korea [2].
authors: Jongseok
authors: J
authors: Lim
authors: Department of Physics, KAIST, Daejeon 305-701, Korea.
authors: Han-gyeol
authors: HG
authors: Lee
authors: Korea Research Institute of Standards and Science, Daejeon 305-340, Korea.
authors: Sangkyung
authors: S
authors: Lee
authors: Korea Research Institute of Standards and Science, Daejeon 305-340, Korea.
authors: Chang-Yong
authors: CY
authors: Park
authors: Department of Physics, KAIST, Daejeon 305-701, Korea.
authors: Jaewook
authors: J
authors: Ahn