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Radios are shrinking. Normal radio receivers use an antenna tuned to a particular range of frequencies, but now researchers have developed an atomic receiver in a tiny glass box that is excellent for spying.
David Anderson at Rydberg Technologies in Michigan and his colleagues built their radio receiver to be more secure and smaller than traditional radios. It starts with a centimetre-sized glass box full caesium vapour. The caesium atoms are prepared so that some of the electrons have more energy than normal, which …