Demonstration of an ac Josephson junction laser

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Science  03 Mar 2017:
Vol. 355, Issue 6328, pp. 939-942
DOI: 10.1126/science.aah6640

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An on-chip microwave source

The active elements of superconducting quantum circuits are typically addressed and controlled using pulses of microwave radiation. The microwaves are usually generated externally and coupled into the circuitry, resulting in rather bulky systems. Cassidy et al. developed an on-chip source of microwaves by using a superconducting Josephson junction inserted in a high-quality microwave cavity. The integrated version should enhance the control capability for manipulating miniaturized quantum circuits.

Science, this issue p. 939


Superconducting electronic devices have reemerged as contenders for both classical and quantum computing due to their fast operation speeds, low dissipation, and long coherence times. An ultimate demonstration of coherence is lasing. We use one of the fundamental aspects of superconductivity, the ac Josephson effect, to demonstrate a laser made from a Josephson junction strongly coupled to a multimode superconducting cavity. A dc voltage bias applied across the junction provides a source of microwave photons, and the circuit’s nonlinearity allows for efficient down-conversion of higher-order Josephson frequencies to the cavity’s fundamental mode. The simple fabrication and operation allows for easy integration with a range of quantum devices, allowing for efficient on-chip generation of coherent microwave photons at low temperatures.

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