A miniaturized SQUID fabricated on a silicon chip
A miniaturized SQUID fabricated on a silicon chip lead image
Superconducting quantum interference devices (SQUIDs) measure magnetic fields with high precision. Their applications include magnetic resonance imaging, magnetoencephalography and quantum computing. For the latter, SQUIDs act as quantum “transistors” and form the basic building blocks of a superconducting quantum computer.
A new article introduces a SQUID that may allow for the integration of superconducting devices with various quantum and non-quantum technologies on the same chip. The novel device is only 4 nanometers thick and 500 nanometers wide with a planar geometry instead of the more common three-dimensional structure. A single-step lithography process was used to fabricate these SQUIDs on silicon chips, and subsequent testing demonstrated good performance.
The researchers had previous experience with superconducting nanowire single-photon detectors and decided to apply the material that plays a significant role in that technology to SQUIDs: niobium nitride. Specifically, they chose to work with nanostructures made of ultra-thin niobium nitride films approximately 10 atomic layers in thickness, which can sustain high magnetic fields and operate at a broad temperature range.
After the films were deposited on a silicon chip, the SQUIDs were processed with only one step of lithography. The researchers then tested the devices in extreme conditions to demonstrate their broad-range applicability. They successfully operated the small and easily-fabricated device within a 20 millikelvin to 5 kelvin temperature range at up to 8 tesla.
Ultimately, the authors hope the advantages of their new SQUID — simple processing, low operating costs and device integrability — will invite researchers from a broad range of disciplines to use the devices for their quantum technological optical and electronic systems.
Source: “On-chip integrable planar NbN NanoSQUID with broad temperature and magnetic-field operation range,” by Itamar Holzman and Yachin Ivry, AIP Advances (2019). The article can be accessed at http://doi.org/10.1063/1.5100259 .
