Researchers at Iowa State University, led by professor Jigang Wang, are using quantum terahertz spectroscopy to explore and control quantum states of matter. The researchers have announced three discoveries based on their studies. The first, reported in Nature Materials, describes how ultrafast pulses of photons — pulsed at trillions of cycles per second — can switch on a state of matter hidden by the superconductive flow of electricity at ultracold temperatures. The researchers demonstrated a tuning knob for switching on exotic, hidden states without changing the temperature. Such a tuning knob, called a quantum quench, could further the research and discovery of nonequilibrium materials. The second finding, reported in Physical Review Letters, describes how the group’s terahertz instrumentation traced electron pairings in materials, revealing a new, light-induced, long-lived state of matter. The third discovery, reported in Nature Photonics, describes how ultrafast pulses of photons can be used like a tuning knob to control and accelerate supercurrents. The ultrafast light pulses break equilibrium symmetry, triggering quantum oscillations that, according to the researchers, cannot be achieved by any other means. Jigang Wang and his research group use quantum terahertz spectroscopy to access, study, and control quantum states of matter. The research group, (l) to (r): Zhaoyu Liu, Liang Luo, Chirag Vaswani, Di Cheng, Jigang Wang, Dinusha Mudiyanselage, Richard H. Kim, and Chuankun Huang. Courtesy of Christopher Gannon/Iowa State University. Wang said that the team would like to use these ultrafast pulses and high frequencies of light to probe smaller scales, in the 1 to 10 nm range. “We’d also like to develop controls using terahertz light for the quantum computation community,” he said. Wang believes that the intense terahertz flashes produced by his laboratory instruments can be a control knob for finding, stabilizing, probing, and potentially controlling exotic states and their unique properties. “We have established a new approach to access and potentially control exotic states of matter,” he said. The research was published in Nature Materials (https://doi.org/10.1038/s41563-018-0096-3), Physical Review Letters (https://doi.org/10.1103/PhysRevLett.121.267001), and Nature Photonics (https://doi.org/10.1038/s41566-019-0470-y).