NMR quantum computing

Abstract:

It has often been asserted that the maximum entropy method can simultaneously suppress noise and enhance resolution in NMR spectra. We examine this claim using a Monte Carlo method to determine the accuracy and precision of line heights and integrals in spectra obtained by various forms of the maximum entropy method. It is shown that maximum entropy processing with lineshape deconvolution produces results that are roughly comparable to least-squares fitting of a model lineshape to the conventional Fourier transform spectrum. © 1991.

Abstract:

The universal quantum homogeniser can transform a qubit from any state to any other state with arbitrary accuracy, using only unitary transformations to perform this task. Here we present an implementation of a finite quantum homogeniser using nuclear magnetic resonance (NMR), with a four-qubit system. We compare the homogenisation of a mixed state to a pure state, and the reverse process. After accounting for the effects of decoherence in the system, we find the experimental results to be consistent with the theoretical symmetry in how the qubit states evolve in the two cases. We analyse the implications of this symmetry by interpreting the homogeniser as a physical implementation of pure state preparation and information scrambling.