By: Patrick Truitt, Senior Member of the Research Staff at SEEQC US

At SEEQC, our advanced facilities and work in superconductive materials offer possibilities for a number of industries and initiatives. We’re pleased to announce we have been selected as one of the companies to advance to phase II of NASA’s Small Business Innovation Research (SBIR) program. After being selected during Phase I of the program, where we established the scientific, technical and commercial merit and feasibility of our proposal, Phase II is focused on the development, demonstration and delivery of the innovation.

Since 1958, NASA has played an important role in the development of cutting-edge materials and technologies. NASA annually invests in U.S. businesses with promising new technologies that show potential for advancing space exploration as well as improving life on Earth.

Two-Dimensional Cryogenic Readout for Far IR Bolometers

For our proposal, SEEQC has received a $749,575 award to develop large-format cryogenic readout circuitry for infrared bolometer arrays. Such arrays are used by NASA to study the cosmic microwave background (CMB) – the radiation left from the earliest moments of the universe’s formation – as well as other astrophysical phenomena.

These bolometers, operating at temperatures of only a few hundred millikelvins, are based on superconducting transition-edge sensors (TES) and require the readout that interfaces with them to be superconducting as well.

Eventually, the signals coming out of these sensors must pass to electronics operating at higher temperatures. To keep the heat load between the two to a minimum (as well as reduce the cost and complexity of the system), it is necessary that the readout circuitry is able to multiplex as well, meaning that several bolometers can be read out on a single signal line. In the present context, multiplexing is usually accomplished by either assigning signals to different frequencies or interleaving them in time.

In Phase I, SEEQC was able to design and fabricate prototype SQUID based time-division multiplexing (TDM) circuits for readout of TES bolometers. A key requirement was to double the circuit density from the current state of the art of being able to read 1 sensor per mm2 pixel to a readout of 2 sensors per mm2. SEEQC’s advanced multilayer fabrication process made such a feat possible. The increase in readout density will enhance future NASA missions’ ability to study the polarization of the CMB and look for tell-tale signs of gravitational waves predicted by inflationary models of the early universe.

The Phase II award will allow SEEQC to continue development, both improving signal-to-noise and scaling up to read out larger TES arrays, with a goal of eventually being able to read out arrays on the order of 1000 pixels. SEEQC will also be applying its expertise in superconducting multi-chip modules to develop the processes necessary to allow its readout array to be connected to a TES array through Indium bump bonds.

Multiplexing is an important technology for any superconducting sensor, particularly as arrays of such sensors grow larger. SEEQC’s foundry can already provide superconducting sensor processes. (In fact, in a separate DOE based SBIR project in collaboration with Lawrence Berkeley National Laboratory, SEEQC is fabricating the TES arrays ourselves.)

By developing readout technologies under the NASA award, SEEQC will be able to offer complete detector packages that combine superconducting sensors arrays and cryogenic readout. In addition to the TDM circuits described above, SEEQC will also be developing other readout approaches, such a microwave SQUID multiplexing, that have the potential to read out even larger sensor arrays and that have application to multiplexed readout of qubit arrays for quantum information processing.

Digital Quantum Computing

This investment from NASA is just as important an opportunity for the scientific and superconducting community at large as it is to our mission to make quantum computing useful, commercially and at scale. The work will help advance our overall understanding and capabilities surrounding readout technology.

Public investments and grants are vital to helping us achieve our goals of providing accessible quantum computers for businesses around the world and are an important validation of the need for our solution. We’re tremendously grateful to NASA for the opportunity to advance our technology and are eager to get to work.