Scientist observed the vibrant stages of BCS superconductor interactions in a Cavity QED by measuring the light leakage from the cavity. Credit: Steven Burrows/Rey and Thompson GroupsResearchers at JILA simulated superconductivity in strontium atoms within an optical cavity to observe rare dynamic stages, consisting of the elusive Phase III, which has implications for quantum physics and technology development.In physics, scientists have actually been amazed by the mystical behavior of superconductors– materials that can perform electrical energy with no resistance when cooled to exceptionally low temperature levels. Within these superconducting systems, electrons collaborate in “Cooper pairs” due to the fact that theyre brought in to each other due to vibrations in the product called phonons.As a thermodynamic stage of matter, superconductors normally exist in a stability state. Recently, scientists at JILA became interested in kicking these products into thrilled states and checking out the occurring dynamics. As reported in a new Nature paper, the theory and experiment groups of JILA and NIST Fellows Ana Maria Rey and James K. Thompson, in cooperation with Prof. Robert Lewis-Swan at the University of Oklahoma, simulated superconductivity under such thrilled conditions utilizing an atom-cavity system.Instead of handling real superconducting products, the scientists harnessed the habits of strontium atoms, laser-cooled to 10 millionths of a degree above absolute absolutely no and levitated within an optical cavity built out of mirrors. In this simulator, the presence or lack of a Cooper pair was encoded in a two-level system or qubit. In this distinct setup, photon-mediated interactions in between electrons were realized in between the atoms within the cavity.Thanks to their simulation, the scientists observed 3 distinct phases of superconducting dynamics, including an uncommon “Phase III” including persistent oscillatory habits predicted by condensed matter physics theorists but never before observed.These findings could lead the way for a deeper understanding of superconductivity and its controllability, using brand-new opportunities for engineering unique superconductors. Moreover, it holds pledge for boosting the coherence time for quantum picking up applications, such as improving the level of sensitivity of optical clocks.Identifying Superconducting PhasesThe JILA group focused on imitating the Barden-Cooper-Schrieffer model, which explains the Cooper pair habits. As co-first author and JILA graduate trainee Dylan Young elaborated: “The BCS design has been around because the 1950s and is central to our understanding of how superconductors work. When condensed matter theorists started studying the out-of-equilibrium characteristics of superconductors, they naturally began with this model.”In the previous few decades, condensed matter theorists have predicted three unique dynamical stages for a superconductor to experience when it progresses. In Phase I, the strength of superconductivity decays quickly to no. On the other hand, Phase II represents a constant state in which superconductivity is preserved.However, the formerly unseen Phase III is the most appealing. “The idea of stage III is that the strength of superconductivity has persistent oscillations with no damping,” discussed JILA finish trainee and co-first author Anjun Chu. “In the phase III routine, rather of suppressing the oscillations, many-body interactions can result in a self-generated routine drive to the system and stabilize the oscillations. Observing this unique behavior requires accurate control of speculative conditions.”To observe this evasive phase, the team leveraged the cooperation of theory from Reys group and experiment from Thompsons group to produce an exactly controlled speculative setup, wishing to fine-tune the experimental criteria to achieve Phase III.Creating Precise Simulations in a Cavity SettingWhile researchers previously attempted to observe Phase III in genuine superconducting systems, measuring this phase has actually stayed elusive due to technical difficulties. “They didnt have the right knobs or readout systems,” explained Young. “On the other hand, our application in an atom-cavity system provides us access to both useful observables and tunable controls to define the characteristics.”Building on previous work, the scientists trapped a cloud of strontium atoms within an optical cavity. In this “quantum simulator”, the atoms imitated Cooper pairs and experienced a cumulative interaction that parallels the tourist attraction experienced by electrons in BCS superconductors. “We think of each atom as representing a Cooper pair,” Young discussed. “An atom in the excited state mimics the presence of a Cooper pair, and the ground state represents the absence of one. This mapping is effective since, as atomic physicists, we understand how to control atoms in methods you simply cant with Cooper pairs.”The researchers used this understanding to induce different phases of dynamics in their simulation by a procedure called “quenching.” As Young elaborated: “Quenching is when we all of a sudden alter or kick our system to see how it reacts. In this case, we prepare our atoms in this highly collective superposition state in between ground and thrilled states. We cause a quench by turning on a laser beam that provides all the atoms different energies.”By altering the nature of this quench, the scientists could see different dynamical phases. They even created a technique to observe the evasive Phase III, which included splitting the cloud of atoms in half. “Using two clouds of atoms with separate control over energy shifts is the essential idea to accomplish Phase III,” Chu remarked.In superconductors, energy levels of electrons can be divided into two sectors, largely occupied or barely occupied, separated by the Fermi level. “Our setup in spin systems does not have a Fermi level intrinsically, so we appraise this using two atomic clouds: one cloud simulates the states listed below the Fermi level, while another cloud mimics the other [quantum] states,” Chu added.To determine the characteristics of the superconductor within the cavity, the researchers tracked the light leaking from the optical cavity in genuine time. Their data found unique points where the simulated superconductor transitioned in between phases, eventually reaching Phase III.Seeing the very first measurements of Phase III surprised much of the group. As Thompson stated: “Actually seeing the wiggles was incredibly gratifying.” For her part in the partnership, Rey was simply as excited to see the theory and experiment align. “On the theory side, BCS superfluids/superconductors could, in concept, be observed in actual degenerate fermionic gases, such as the ones Debbie Jin at JILA taught us how to create. It has actually been tough to observe the dynamical stages in these systems. We anticipated back in 2021 that all BCS dynamical phases could instead manifest in an atom-cavity experiment. It was so great to see our theory forecasts come true and actually observe the dynamical phases in a genuine experiment!”Underlying Physics with Broader ApplicationsWhile observing Phase III within their system was a considerable accomplishment, the team also discovered that the determined behaviors could have broader implications beyond superconductivity. As Thompson elaborated, “In regards to the underlying design that you use to explain it, it ends up that this BCS design has all these connections to various kinds of physics at different energy scales, temperature scales, and timescales, from superconductors to neutron stars to quantum sensing units!”Rey added: “These observations really open a path to simulate unconventional superconductors with remarkable topological residential or commercial properties for recognizing robust quantum computers. It will be wonderful to emulate even toy models of these complex systems in our atom-cavity quantum simulator.”For more on this research study, see Strontium Unlocks Quantum Secrets of Superconductivity.Reference: “Observing dynamical phases of BCS superconductors in a cavity QED simulator” by Dylan J. Young, Anjun Chu, Eric Yilun Song, Diego Barberena, David Wellnitz, Zhijing Niu, Vera M. Schäfer, Robert J. Lewis-Swan, Ana Maria Rey and James K. Thompson, 24 January 2024, Nature.DOI: 10.1038/ s41586-023-06911-xThis work was supported in part by the Quantum Systems Accelerator, part of the United States Department of Energy, Office of Science, National Quantum Information Science Research Centers.
Credit: Steven Burrows/Rey and Thompson GroupsResearchers at JILA simulated superconductivity in strontium atoms within an optical cavity to observe unusual vibrant stages, including the elusive Phase III, which has implications for quantum physics and innovation development.In physics, scientists have been fascinated by the mystical behavior of superconductors– materials that can perform electrical power with no resistance when cooled to extremely low temperature levels. In this distinct setup, photon-mediated interactions between electrons were understood in between the atoms within the cavity.Thanks to their simulation, the researchers observed 3 unique stages of superconducting dynamics, including an uncommon “Phase III” including relentless oscillatory behavior predicted by condensed matter physics theorists but never ever before observed.These findings could pave the way for a deeper understanding of superconductivity and its controllability, using brand-new avenues for engineering distinct superconductors. In contrast, Phase II represents a constant state in which superconductivity is preserved.However, the previously unobserved Phase III is the most interesting.”To observe this elusive stage, the group leveraged the collaboration of theory from Reys group and experiment from Thompsons group to create a specifically managed experimental setup, hoping to tweak the experimental parameters to accomplish Phase III.Creating Precise Simulations in a Cavity SettingWhile researchers previously attempted to observe Phase III in real superconducting systems, determining this phase has actually remained evasive due to technical problems. Their data found distinct points where the simulated superconductor transitioned in between stages, eventually reaching Phase III.Seeing the first measurements of Phase III surprised many of the group.
