Fermilab News Today
The scientific community has struggled with dark matter for nearly a century. This unseen element, thought to make up most of the universe’s mass, is one of physics’ biggest mysteries. A cutting-edge quantum detector developed by a team may reveal this molecule.
The Challenge of the Invisible
Since dark matter rarely interacts with light and ordinary stuff, traditional techniques cannot examine it. Because dark matter’s composition is unknown, researchers must look at a huge variety of particle masses and signal frequencies. Researchers require detectors with unprecedented sensitivity to catch even the smallest signals to find a needle in this cosmic haystack.
Fermilab, Chicago, Stanford, and NYU researchers proposed an electronically controllable quantum detector. The dark photon, a hypothetical dark matter particle that is a distant relative of the common photon, or particle of light, is the target of this apparatus.
A Radio for the Dark Sector
Dark photons are thought to occur in a narrow frequency range. A gadget must be adjusted to a frequency to detect it, like a radio. In the past, this was a mechanical, slow procedure. But the new detector makes use of a novel method known as flux tuning.
Superconducting quantum interference devices (SQUIDs) in three-dimensional microwave cavities are the core of this technology. The SQUID can detect even the smallest signals since it is superconducting and has no energy resistance. Scientists use electromagnetic flux instead of physically shifting components to alter frequencies in the SQUID. The frequency that the microwave cavity “listens” to is altered by this electronic “pendulum” that modifies the device’s operating speed.
“We apply electromagnetic flux to the SQUID, precisely controlling its ability to oppose changes in electricity flowing through it, instead of physically turning a dial to a specific frequency like with a radio,” stated Fang Zhao, a former postdoctoral researcher at Fermilab who oversaw the project.
Breaking the Speed Limit
There are significant benefits to electrical tuning versus mechanical techniques. To modify the form of a cavity or add mechanical components to circuits, conventional tunable detectors need physical force. Because qubit-based detectors need to function at extremely low cryogenic temperatures, this is troublesome. Mechanical components frequently seize or shatter under such severe circumstances. Heat is produced more significantly by mechanical motion.
In the domain of quantum mechanics, heat is noise. The precise state that gives these sensors their extraordinary precision, quantum coherence, can be destroyed by even a tiny quantity of thermal energy, obscuring delicate signals. To maintain the “quiet” environment required to detect a dark photon, flux tuning produces nearly no heat.
The team’s first experiments produced startling findings. The researchers were able to reach a scanning rate at least 20 times faster than that of mechanical tuning by scanning a 22-megahertz range in just three days. Building on years of earlier study, this particular search helped scientists narrow down the potential frequency ranges where dark matter might exist even though it failed to locate a dark photon.
The Path Forward
As a proof of concept, the detector’s current version has one cavity and one SQUID. But the group is already aiming for a far bigger scale. Researchers think they may soon be able to use a single adjustable element to combine ten, fifty, or even more cavities. Researchers might scan a frequency range that is 50 times greater than what is currently feasible with the use of such an array.
Ziqian Li, a former graduate student at the University of Chicago who participated in the project, pointed out that in the absence of this electrical tuning capability, billions of independent detectors would need to be built to detect a signal. With flux-tunable technology, a full-coverage search for the dark photon is now possible.
Aaron Chou, a physicist at Fermilab, stated, “Our primary objective is to construct a detector that is more sensitive than any other detector that has been constructed to date; we have successfully achieved this.” By establishing the detector’s compatibility with qubit-based signal readouts.
This research was enabled by the U.S. Department of Energy’s Quantum Information Science Enabled Discovery initiative, which advances quantum sensors for the next frontier of science. With Fermilab’s continued use of its proficiency in low-noise electronics, the enigma of dark matter might soon be resolved.
