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Presenter: Dr. Tomoyuki Yamakami - School of Information Technology and Engineering, University of Ottawa
Supervisor: Dr. R. Nigel Horspool, Chair, Department of Computer Science

Date: Mon, January 27, 2003
Time: 13:30:00 - 14:30:00
Place: Engineering Office Wing Building, (EOW) Room # 430

ABSTRACT

ABSTRACT:

The unit of quantum information is a quantum bit (qubit), defined as a unit-norm vector in a 2-dimensional Hilbert space. Such a qubit can be realized by an optical photon, a nuclear spin of an atom, or an energy level of a quantum oscillator. To know the content of the qubits, we perform measurements. A quantum string (qustring), a sequence of qubits, is called separable if at least two groups of qubits are mutually "independent" and thus, any measurement of one group does not disturb another group. A qustring is entangled if it is not separable. A prominent use of entanglement is quantum teleportation in which one can transmit qubit information without physically sending the qubit.

Quantum entanglement can be viewed as a physical resource and be quantified. Most work in the literature took information-theoretical approaches to quantify entanglement (such as, entanglement distillation, entanglement cost, etc.). We rather study entanglement from a computational-complexity perspective. In particular, we study two measures: computational approximability and computational distinguishability for entanglement ensembles. We show important relationships between computational approximability and distinguishability and discuss the usefulness of these concepts.

This talk is based on the speaker's recent efforts to understand the nature of entanglement as a complexity theoretician. The first half of the talk gives a brief introduction to quantum computation and information theory.

Note: Dr. Tomoyuki Yamakami is a candidate for a faculty position in the Department of Computer Science.