US Patent 7277872 - Quantum computing with resource state

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Quantum computing usually depends on entanglement between properties (e.g. polarization, spin) of fundamental particles (e.g. photons, electrons) which allows for a degree of parallel processing which is advantageous for certain computational problems. However, a problem of decoherence exists that leads to a limit in the number of fundamental particles that can be entangled. In order to overcome this problem this patent teaches a technique of using a common resource state entangled with a plurality of quantum states (as opposed to a plurality of separately entangled quantum states). Claim 1 reads:

1. A method for quantum computing, the method which comprises: providing a plurality of quantum systems each having at least two different states; preparing a resource state of the quantum systems wherein all of the quantum systems are in a common superimposed entangled state; in the resource state, making one-system measurements on the quantum systems; processing outcomes of the one-system measurements; and outputting a result of the processing.