Professor Artur Ekert FRS

Abstract:

We provide a physical prescription based on interferometry for introducing the total phase of a mixed state undergoing unitary evolution, which has been an elusive concept in the past. We define the parallel transport condition that provides a connection form for obtaining the geometric phase for mixed states. The expression for the geometric phase for mixed state reduces to well known formulas in the pure state case when a system undergoes noncyclic and unitary quantum evolution.

Abstract:

A scheme for implementing quantum logic operations within a cavity of QED configuration is presented. This scheme is particularly suitable for the direct implementation of some useful many-qubit quantum gates. From a general point of view, the scheme is analogous to the linear ion trap scheme, except that the high-Q cavities play the role of the ions, and the atoms play the role of the quantum bus.

Abstract:

We propose a scheme for quantum computing using high-Q cavities in which the qubits are represented by single cavity modes restricted in the space spanned by the two lowest Fock states. We show that single qubit operations and universal multiple qubit gates can be implemented using atoms sequentially crossing the cavities.