Large scale quantum information processor

But, what would be an adequate system for a NMR large-scale quantum information processor Basically a system containing a large number of isolated qubits, perhaps thousands, in which the interaction between any pair of them could be controlled, and the state of each single qubit could be accessed by measurement. The need of such a system may sound hopeless, since conventional NMR sensitivity is limited to about 10 spins But that only means we have to look for something unconventional, perhaps combining the best aspects and capabilities of different techniques. 

In the previous section we have described some very ingenious proposals which, if implemented in practice, could lead to a large scale quantum information processor through NMR. It is important to emphasize that those proposals circumvent the scaling problem present in liquid-state NMR QIP experiments. However, whatever the sample architecture may be, it seems unavoidable the need to detect the NMR signal of very small spin concentrations. Ideally, single spin detection should be possible. Less than two decades ago, such a strict demand could sound hopeless conventional ESR needs a concentration of some... 

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