Researchers at Delft University of Technology made a monumental breakthrough by developing an on-chip microwave laser. This device is the first of its kind after it was produced from a Josephson junction, embedded in a superconducting microwave cavity. The lasers are low-heat and highly efficient, making them an ideal component for operating quantum computers.
The Josephson junction is made when a thin layer of non-superconducting material is sandwiched between two layers of superconducting material. This junction is named after Brian Josephson, the Nobel prize-winning scientist who accurately predicted that pairs of superconducting electrons (called copper pairs), would be able to “tunnel” through thin, non-superconducting barriers from one superconductor to another.
This quantum phenomenon is called the Josephson effect—the basic concept of superconductivity. Researchers developed a device composed from a nanoscale Josephson junction, and paired it with a high-quality factor superconducting micro-cavity. The microwave photons are produced and bounce back and forth between two layers or “mirrors” of superconducting material when the device is cooled below one-degree Kelvin.
Using less than one picoWatt of power to emit, the microwave light beam that’s emitted from the cavity is extremely energy-efficient, being more than 100 billion times less than a light globe—especially when compared to current microwave sources. Due to their inefficiency, conventional lasers aren’t considered to be as ideal to use in quantum computers, especially considering how they lose a lot of heat when the laser is being used. The systems are less-bulkier and exert greater control in manipulating quantum circuits, which could result from generating microwaves inside the chip itself, rather than doing so externally like conventional devices do.
Researchers intend on using Josephson junctions made from nanowires for microwave bursts, which can be used to quickly control the various quantum components, along with trying to produce “amplitude-squeezed” light. This form of light has smaller intensity fluctuations when compared to conventional lasers, and is considered to be a vital requirement when operating quantum communication protocols.
