Byoung Ham, Gwangju Institute of Science and Technology
Quantum coherence control in an inhomogeneously broadened lambda-type solid state ensemble has been studied for quantum memories over decades. Unlike akali atoms, the optically excited spin coherence in a rare-earth doped solid is sufferred from a serious spin dephasing problem due to spin inhomogeneity. Thus, solid state quantum memory protocols such as AFC and gradient echo have been effctively demonstrated only for optical transitions, whose coherence time is far shorter than ms. Resonant Raman rephasing applied to solve this spin dephasing problem, however, results in spin population inversion causing spintaneous emssion noise. Here in this talk, a counterintuitive read-out approach is presented for a wavelength converted quantum memory, the so-called a controlled echo. The controlled echo can also be manipulated for ultralong photon storage much longer than a given parameter up to minutes or even hours without using dynamic decoupling or zero first-order Zeeman effects. For scalable quantum computing, several single qubit gate schemes are presented, e.g., for Hadamard and Pauli gates. Using Bell measurement in a two-qubit system, controlled-NOT and controlled-Z gates are also presented. Unlike most single object-based qubit systems, the present ensemble qubit is intrinsically free from the decoherence acceleration inevitable in a multiple qubit-entangled system such as in a cluster state.
About the speaker
Professor Ham’s research specialty is in quantum nonlinear optics of light matter interactions for the quantum coherence control in a rare-earth doped solid. He is a director of the center for photon information processing at GIST, S. Korea, and has been serving for the journal of Applied Optics (OSA) as a topical editor and for Optics Communications (Elsevier) as the advisory editorial board member. Currently he is visitng Prof. K. Choi at IQC of University of Waterloo as a visiting professor.
*** Coffee and snacks to be served at 2:00. Talk begins at 2:30.
Room location: Mike and Ophelia Lazaridis Quantum-Nano Centre (QNC) Room 0101