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Physicists Entangle 2 Atoms via Microwaves

Physicists at the National Institute of Standards and Technology have entangled two separated electrically charged atoms (ions) by manipulating them with microwaves.

The research (Ref.: C. Ospelkaus, et al., Microwave Quantum Logic Gates for Trapped Ions, Nature, 2011; [DOI:10.1038/nature10290]) suggests it may be possible to replace room-sized laser-based quantum computing attempts with miniaturized, commercial microwave technology.

The team is the first to position microwave sources just 30 micrometers away from the ions to create the conditions enabling entanglement, the quantum phenomenon expected to be crucial for transporting information in quantum computation.

The scientists 'entangled' the ions by adapting a technique first developed with lasers. If the microwaves’ magnetic fields gradually increase across the ions in just the right way, the ions’ motion can be excited depending on the spin orientations, and the spins can become entangled in the process.

The properties of the entangled ions are linked, so a measurement of one ion would reveal the state of the other.

Compared to complex, expensive laser sources, microwave components could be expanded and upgraded more easily to build practical systems of thousands of ions for quantum computing and simulations. Usage of microwaves also could reduces errors introduced by instabilities in laser beam pointing and power as well as laser-induced spontaneous emissions by ions.