IBM Quantum’s tantalum breakthrough redefines superconducting electronics stability
A team of researchers from IBM Quantum has made a breakthrough in superconducting electronics. They successfully created Josephson junctions using tantalum electrodes and a tantalum nitride tunnel barrier, promising better stability and performance compared to traditional materials.
The junctions were built on 300mm wafers using standard microchip manufacturing techniques. Early tests show they maintain their properties for months without degrading, even in normal storage conditions.
Traditional Josephson junctions rely on aluminium oxide as the insulating barrier. However, this material can degrade over time and has processing limitations. The IBM team replaced it with tantalum nitride, which offers improved thermal and environmental stability.
The researchers, including Ekta Bhatia, Jack Lombardi, and Tuan Vo, used atomic layer deposition to create ultra-thin tantalum nitride layers. These layers act as tunnel barriers between tantalum electrodes. The resulting junctions achieved a critical current density of 76 microamperes per square micrometre with a 4-nanometre barrier.
Testing revealed that the junctions exceeded 1000 amperes per square centimetre in critical current density. They also showed low subgap leakage currents, confirming high barrier integrity and interface quality. Electrical measurements and transmission electron microscopy were used to verify performance and barrier quality.
Over 140 days of ambient storage, the junctions displayed no measurable degradation in resistance. The team also demonstrated predictable scaling of performance with barrier thickness, making the technology more reliable for practical applications.
The new tantalum-based junctions could replace less stable aluminium oxide designs in superconducting circuits. Their long-term stability and compatibility with standard microchip fabrication methods make them a strong candidate for future quantum and classical computing applications. The research marks a step forward in developing more durable and efficient superconducting electronics.
