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Decoding the Universe: How Cryogenic Electronics Help Detect Dark Energy and Dark Matter

Equal1 Labs, in collaboration with the United States SLAC National Accelerator Laboratory, is developing cryogenic control electronics, a critical component in the study of cosmic phenomena such as Dark Energy, Dark Matter, and potential primordial gravitational waves.

The IEEE International Symposium on Circuits and Systems (ISCAS) serves as the flagship conference of the IEEE Circuits and Systems (CAS) Society. At ISCAS2023, Equal1's Vice President of Analog Engineering, Imran Bashir, presented on the role of cryogenic control electronics in studying the Cosmic Microwave Background (CMB) and detecting Dark Energy and Dark Matter.

Dark Energy and Dark Matter, despite being invisible and only inferred through their gravitational effects, are two significant components of the universe. Dark Matter, an inferred form of invisible matter, constitutes about 85% of the universe's matter. Its presence is deduced from its gravitational influence on visible matter, like stars and galaxies. Dark Energy, on the other hand, pervades all space and is postulated to be driving the accelerating expansion of the universe, accounting for about 68% of the universe's total energy.

Instruments such as SQUID (Superconducting Quantum Interference Devices) and TES (Transition Edge Sensor) arrays are integral to studying the Cosmic Microwave Background (CMB) and addressing fundamental questions about our universe.

At ISCAS2023, Imran elaborated on the cryogenic control electronics that drive SQUID and TES arrays, both of which are specialized detectors that contribute to the exploration of the universe's deepest mysteries for the CMB-S4 (Cosmic Microwave Background Stage-4) project.

The CMB-S4 project, a ground-breaking ground-based experiment, aims to scrutinize the cosmic microwave background(CMB), the remnant radiation from the Big Bang. The project deploys telescopes stationed at the South Pole and in the Chilean Atacama desert, armed with over 500,000 cryogenically-cooled superconducting detectors. Over a period of seven years, these telescopes will scan the skies with the objective of making transformative discoveries in fields like fundamental physics, cosmology, astrophysics, and astronomy. The project has the backing of the Department of Energy Office of Science and the National Science Foundation.

Just as with quantum computing technologies, the scaling of cryogenic electronics in TES arrays is a crucial consideration, leading Equal1 and SLAC National Accelerator Laboratory to submit a joint proposal to the Department of Energy (DoE). The collaboration is working on designing critical control electronics using the commercial 22nm FD-SOI CMOS foundry process of GlobalFoundries Inc.

Imran outlined the core concepts of the circuit and system architecture in the session titled 'Scalability of Quantum Computing Chip Architectures: A Circuit & System Perspective' at ISCAS2023 in Monterey, CA. He proposed a streamlined and efficient apparatus for a CMB detector, which employs a cryogenic controller IC for a large TES array. This apparatus markedly reduces the passive heat load by curtailing the number of wires stemming from the room-temperature electronics. In the current proposal, the cryogenic controller is responsible for two vital circuit functions: the row multiplexer and the bias DAC. These low-power and low-noise circuits can be scaled to manage a large number of channels necessary for the next generation of CMB telescopes.

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