1,643 research outputs found
Scaling issues in ensemble implementations of the Deutsch-Jozsa algorithm
We discuss the ensemble version of the Deutsch-Jozsa (DJ) algorithm which
attempts to provide a "scalable" implementation on an expectation-value NMR
quantum computer. We show that this ensemble implementation of the DJ algorithm
is at best as efficient as the classical random algorithm. As soon as any
attempt is made to classify all possible functions with certainty, the
implementation requires an exponentially large number of molecules. The
discrepancies arise out of the interpretation of mixed state density matrices.Comment: Minor changes, reference added, replaced with publised versio
A fault-tolerant one-way quantum computer
We describe a fault-tolerant one-way quantum computer on cluster states in
three dimensions. The presented scheme uses methods of topological error
correction resulting from a link between cluster states and surface codes. The
error threshold is 1.4% for local depolarizing error and 0.11% for each source
in an error model with preparation-, gate-, storage- and measurement errors.Comment: 26 page
Experimental magic state distillation for fault-tolerant quantum computing
Any physical quantum device for quantum information processing is subject to
errors in implementation. In order to be reliable and efficient, quantum
computers will need error correcting or error avoiding methods. Fault-tolerance
achieved through quantum error correction will be an integral part of quantum
computers. Of the many methods that have been discovered to implement it, a
highly successful approach has been to use transversal gates and specific
initial states. A critical element for its implementation is the availability
of high-fidelity initial states such as |0> and the Magic State. Here we report
an experiment, performed in a nuclear magnetic resonance (NMR) quantum
processor, showing sufficient quantum control to improve the fidelity of
imperfect initial magic states by distilling five of them into one with higher
fidelity
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