The sound of a human voice singing “Mary had a little lamb” has been played by a radio receiver that exploits the quantum properties of a cloud of atoms – 140 years after the nursey rhyme was famously recorded by Thomas Edison. In Edison’s case, sound was recorded by using a stylus to rearrange the positions of vast numbers of aluminium atoms on a foil-wrapped cylinder. Now, David Anderson, Rachel Sapiro and Georg Raithel at Rydberg Technologies in Ann Arbor Michigan have used a cloud of highly-excited caesium atoms to store and playback AM and FM radio signals.
The concepts behind their feat promise to address some of the underlying challenges of creating radio communication systems that offer information security and resilience against electromagnetic interference. In principle, quantum radios based on clouds of atoms could be immune to intense interfering fields while transmitting clear signals that cannot be tampered with.
The receiver built by Anderson and colleagues uses Rydberg atoms. Such atoms are in highly-excited quantum states in which some electrons spend most of their time relatively far away from the atomic nucleus. As a result, Rydberg atoms can function as tiny antennas that are extremely responsive to electromagnetic fields.
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