As plans to develop more powerful particle accelerators unfold, so does the problem of how to sift through the chaos of the subatomic particles unleashed from the accelerators’ collisions. To address this, researchers from the U.S. Department of Energy’s Fermi National Accelerator Laboratory (Fermilab), Caltech, NASA's Jet Propulsion Laboratory (JPL; managed by Caltech), and other collaborating institutions have developed a novel high-energy particle detection instrumentation approach that leverages the power of quantum sensors — devices capable of precisely detecting single particles. The research team, which also includes collaborators at the University of Geneva and Federico Santa María Technical University in Chile, tested its new technology, called superconducting microwire single-photon detectors (SMSPDs), for the first time at Fermilab near Chicago. They exposed the quantum sensors to high-energy beams of protons, electrons, and pions, and demonstrated that the sensors were highly efficient at detecting the particles with improved time and spatial resolution compared to traditional detectors. The SMSPDs can precisely detect single particles at a time. The detectors were designed and fabricated at JPL and commissioned at the INQNET-Caltech labs. Courtesy of Cristián Peña/Fermilab. "This is a significant step toward developing advanced detectors for future particle physics experiments," said co-author Si Xie, a scientist at Fermilab who has a joint appointment at Caltech as a research scientist. “This is just the beginning,” he said. “We have the potential to detect particles lower in mass than we could before, as well as exotic particles like those that may constitute dark matter.” The quantum sensors used in the study are similar to a related family of sensors (called superconducting nanowire single-photon detectors, or SNSPDs), which have applications in quantum networks and astronomy experiments. For example, researchers at JPL recently used them in the Deep Space Optical Communications experiment, a technology demonstration that used lasers to transmit high-definition data from space to the ground. Spiropulu, Xie, and other scientists from Fermilab, Caltech, and JPL have also used the SNSPD sensors in quantum networking experiments, in which they teleported information across long distances — an important step in developing a quantum internet in the future. That program, called Intelligent Quantum Networks and Technologies (INQNET), was jointly founded in 2017 by Caltech and AT&T. For the particle physics tests, the researchers used SMSPDs rather than the SNSPDs, because they have a larger surface area for collecting the sprays of particles. They used the sensors to detect charged particles for the first time, an ability that is not needed for quantum networks or astronomy applications but is essential for particle physics experiments. “The novelty of this study is that we proved the sensors can efficiently detect charged particles,” Xie said. The SMSPD sensors can also more precisely detect particles in both space and time. “We call them 4D sensors because they can achieve better spatial and time resolution all at once,” Xie said. “Normally in particle physics experiments, you have to tune the sensors to have either more precise time or spatial resolution, but not both simultaneously.” When researchers analyze the bunches of particles that fly out of high-speed collisions, they want to be able to precisely trace their paths in space and time. As an analogy, if one were to track a person hiding in a crowd of people, they would want enough spatial resolution to pick out individuals, as well as enough time resolution to follow their movements. If images are only taken every ten seconds, the person could be lost, but if pictures are taken every second, the odds of tracking the person increase. “In these collisions, you might want to track the performance of millions of events per second,” Spiropulu said. “You are swamped with hundreds of interactions, and it can be hard to find the primary interactions with precision. Back in the 1980s, we thought having the spatial coordinates were enough, but now, as the particle collisions become more intense, producing more particles, we also need to track time.” The research was published in the Journal of Instrumentation (www.doi.org/10.1088/1748-0221/20/03/P03001).