Demonstration of Two-Qubit Algorithms with a Superconducting Quantum Processor
Leo DiCarlo
Yale Univ.
Mercredi 01/04/2009, 11:15
SPEC Salle Itzykson, Bât.774, Orme des Merisiers
By harnessing the superposition and entanglement of
physical states, quantum computers could outperform their classical
counterparts in solving problems of technological impact, such as
factoring large numbers and searching databases. A quantum processor
executes algorithms by applying a programmable sequence of gates to an
initialized register of qubits, which coherently evolves into a final
state containing the result of the computation. Simultaneously meeting
the conflicting requirements of long coherence, state preparation,
universal gate operations, and qubit readout makes building quantum
processors challenging. Few-qubit processors have already been shown in
nuclear magnetic resonance, cold ion trap and optical systems, but a
solid-state realization has remained an outstanding challenge. Here we
demonstrate a two-qubit superconducting processor and the implementation
of the Grover search and Deutsch-Jozsa quantum algorithms. We employ a
novel two-qubit interaction, tunable in strength by two orders of
magnitude on nanosecond time scales, which is mediated by a cavity bus
in a circuit quantum electrodynamics (cQED) architecture. This
interaction allows generation of highly-entangled states with
concurrence up to 94%. Although this processor constitutes an important
step in quantum computing with integrated circuits, continuing efforts
to increase qubit coherence times, gate performance and register size
will be required to fulfill the promise of a scalable technology.