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Quantum physics: Signature shift

Nature volume 456, page 549 (04 December 2008) | Download Citation

The discovery of the Lamb shift in 1947 was a key factor in the development of quantum electrodynamics (QED). This slight discrepancy between the predicted and observed energy levels of electrons in a hydrogen atom was eventually explained by QED as the effect of virtual photons flickering in and out of existence in a vacuum. Now that effect has been replicated in an electrical circuit by Andreas Wallraff at ETH Zurich in Switzerland and his colleagues.

Their work uses 'artificial atoms', quantum devices designed to have an energy spectrum resembling that of real atoms. Tuning a coupling between such artificial atoms and a microwave transmission line containing a strong vacuum allowed them to produce a Lamb shift of 1.4% for a typical emission line.

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