Experimental Quantum Computation with Nuclear Spins in Liquid Solution

摘要

We have taken significant steps towards the realization of a practicalquantum computer: using nuclear spins and magnetic resonance techniques at roomtemperature, we provided proof of principle of quantum computing in a series ofexperiments which culminated in the implementation of the simplest instance ofShor's quantum algorithm for prime factorization (15=3x5), using a seven-spinmolecule. This algorithm achieves an exponential advantage over the best knownclassical factoring algorithms and its implementation represents a milestone inthe experimental exploration of quantum computation. These remarkable successeshave been made possible by the synthesis of suitable molecules and thedevelopment of many novel techniques for initialization, coherent control andreadout of the state of multiple coupled nuclear spins. Furthermore, we devisedand implemented a model to simulate both unitary and decoherence processes inthese systems, in order to study and quantify the impact of varioustechnological as well as fundamental sources of errors. In summary, this workhas given us a much needed practical appreciation of what it takes to build aquantum computer. While liquid NMR quantum computing has well-understoodscaling limitations, many of the techniques that originated from this researchmay find use in other, perhaps more scalable quantum computer implementations.