The ability to live in coherent superpositions is a signature trait of quantum systems and constitutes an irreplaceable resource for quantum-enhanced technologies. However, decoherence effects usually destroy quantum superpositions. It was recently predicted that, in a composite quantum system exposed to dephasing noise, quantum coherence in a transversal reference basis can stay protected for an indefinite time.
View Article and Find Full Text PDFThe realization of an all-heteronuclear 5-qubit nuclear magnetic resonance quantum computer is reported, from the design and synthesis of a suitable molecule through the engineering of a prototype 6-channel probe head. Full control over the quantum computer is shown by a benchmark experiment.
View Article and Find Full Text PDFPhilos Trans A Math Phys Eng Sci
October 2012
Steering quantum dynamics such that the target states solve classically hard problems is paramount to quantum simulation and computation. And beyond, quantum control is also essential to pave the way to quantum technologies. Here, important control techniques are reviewed and presented in a unified frame covering quantum computational gate synthesis and spectroscopic state transfer alike.
View Article and Find Full Text PDFThe repertoire of problems theoretically solvable by a quantum computer recently expanded to include the approximate evaluation of knot invariants, specifically the Jones polynomial. The experimental implementation of this evaluation, however, involves many known experimental challenges. Here we present experimental results for small-scale approximate evaluation of the Jones polynomial by nuclear magnetic resonance (NMR); in addition, we show how to escape from the limitations of NMR approaches that employ pseudopure states.
View Article and Find Full Text PDFAn exact correspondence is found between the quantum dynamics of three isotropically coupled spins 1/2 and the dynamics of three coupled classical oscillators. This correspondence is demonstrated by experimentally simulating the polarization transfer functions of an isotropic mixing TOCSY experiment with a set of mechanically coupled pendulums. The extend to which the exact correspondence holds is analyzed and it is shown that it breaks down for systems consisting of more than three coupled spins.
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