Cascades in the Quantum World: How Superconducting Junctions Detect the Tiniest Signals
By using the domino effect of cascade multiplication, superconducting detectors can register even the faintest traces of radiation. While traditional photomultipliers work well for visible light, they fail at lower frequencies such as terahertz and microwaves. Superconductors overcome this limitation, opening new possibilities for quantum technology and for exploring the hidden signals of the universe. Professor Vladimir Krasnov and PhD Roger Cattaneo from Fysikum have worked together with Artemii E. Efimov, Kirill I. Shiianov and Oliver Kieler. The article was published recently in Nature Communications.
The energy-phase diagram of a Josephson junction array.
Researchers are developing a new class of cascade-amplified superconducting detectors that use arrays of Josephson junctions – tiny quantum devices where superconducting currents can tunnel through an insulating barrier. When a single photon is absorbed, the coupling between junctions causes many of them to switch in an avalanche-like chain reaction. This “domino effect” greatly amplifies the signal and reduces noise, making it possible to register even the faintest microwave (MW) and terahertz (THz) radiation. Prototypes using both low-temperature niobium-based junctions and high-temperature cuprate superconductors show clear advantages over conventional single-junction detectors. These findings pave the way for ultra-sensitive broadband detectors, with applications ranging from quantum technologies to astrophysical observations.
