Spin-squeezed states in the preferred optical transitions with little outside noise have been tough to prepare and maintain.One specific method to create a spin-squeezed state, or squeezing, is by positioning the clock atoms into an optical cavity, a set of mirrors where light can bounce back and forth numerous times. Depending on how superradiance is used, it can lead to entanglement, or additionally, it can instead interrupt the preferred quantum state.In a previous study, done in a cooperation between JILA and NIST Fellows, Ana Maria Rey and James Thompson, the scientists discovered that multilevel atoms (with more than two internal energy states) provide special chances to harness superradiant emission by instead inducing the atoms to cancel each others emissions and stay dark.Now, reported in a pair of new papers published in Physical Review Letters and Physical Review A, Rey and her group discovered a method for how to not only develop dark states in a cavity, however more significantly, make these states spin squeezed. Rey and her group have actually shown that dark states could be recognized when atoms prepared in particular initial states were placed inside a cavity.”The cool thing is that the spin squeezing produced at these brilliant points can then be moved into a dark state where, after proper positioning, we can turn off the laser and protect the squeezing,” Sundar adds.This transfer works by first driving the atoms into a valley of the superradiant potential and then using lasers with proper polarizations (or directions of light oscillations) to coherently line up the squeezed instructions, making the squeezed states immune to superradiance.The transfer of squeezed states into dark states not just preserved the reduced noise characteristics of the squeezed states, but likewise guaranteed their survival in the absence of being driven by an external laser, a vital factor for practical applications in quantum metrology.While the study released in Physical Review Letters used only one polarization of the laser light to cause spin squeezing, creating 2 squeezed modes, the Physical Review A paper took this simulation further by utilizing both polarizations of laser light, resulting in 4 spin-squeezed modes (two modes for each polarization). By overcoming the constraints of superradiance by means of the generation of dark knotted states, physicists either shop the knotted states utilizing the atoms as a memory (allowing for the retrieval of information from these states) or inject the knotted state into a clock or interferometer sequence for quantum-enhanced measurements.References:”Squeezing Multilevel Atoms in Dark States through Cavity Superradiance” by Bhuvanesh Sundar, Diego Barberena, Ana Maria Rey and Asier Piñeiro Orioli, 17 January 2024, Physical Review Letters.DOI: 10.1103/ PhysRevLett.132.033601″Driven-dissipative four-mode squeezing of multilevel atoms in an optical cavity” by Bhuvanesh Sundar, Diego Barberena, Ana Maria Rey and Asier Piñeiro Orioli, 17 January 2024, Physical Review A.DOI: 10.1103/ PhysRevA.109.013713 This research was supported by the U.S. Department of Energy, Office of Science, National Quantum Information Science Research Centers Quantum Systems Accelerator, and the National Institute of Standards and Technology (NIST).
Multilevel atoms on a superradiance potential “rollercoaster” inside an optical cavity. The system can be tuned to create squeezing in a dark state where it will be immune to superradiance. CreditSteven Burrows/Rey GroupPhysicists are pushing the limits of atomic clock accuracy by utilizing spin-squeezed states, attaining groundbreaking control over quantum sound and entanglement, leading to possible leaps in quantum metrology.While atomic clocks are already the most precise timekeeping gadgets in deep space, physicists are striving to improve their accuracy even further. One method is by leveraging spin-squeezed states in clock atoms. Spin-squeezed states are knotted states in which particles in the system conspire to cancel their intrinsic quantum noise. These states, therefore, offer fantastic chances for quantum-enhanced metrology considering that they enable more precise measurements. Yet, spin-squeezed states in the desired optical transitions with little outside noise have been difficult to prepare and maintain.One specific way to generate a spin-squeezed state, or squeezing, is by positioning the clock atoms into an optical cavity, a set of mirrors where light can bounce back and forth sometimes. In the cavity, atoms can integrate their photon emissions and discharge a burst of light far brighter than from any one atom alone, a phenomenon referred to as superradiance. Depending on how superradiance is utilized, it can result in entanglement, or additionally, it can instead interrupt the desired quantum state.In a previous study, done in a partnership in between JILA and NIST Fellows, Ana Maria Rey and James Thompson, the researchers found that multilevel atoms (with more than 2 internal energy states) provide unique opportunities to harness superradiant emission by rather causing the atoms to cancel each others emissions and remain dark.Now, reported in a set of brand-new documents published in Physical Review Letters and Physical Review A, Rey and her group discovered a method for how to not just develop dark states in a cavity, however more importantly, make these states spin squeezed. Their findings might open exceptional chances for producing entangled clocks, which could press the frontier of quantum metrology in a fascinating way.Rolling Into a Dark State on a Superradiant Roller CoasterFor a number of years, Rey and her team have studied the possibility of utilizing superradiance by forming dark states inside a cavity. Because dark states are unique setups where the usual paths of light emission interfere destructively, these states do not give off light. Rey and her team have actually shown that dark states could be recognized when atoms prepared in particular preliminary states were put inside a cavity. Prepared in this method, the quantum states could stay impervious to the results of superradiance or light emission into the cavity. The atoms could still release light outside the cavity, but at a rate that is much slower than superradiance.Former JILA postdoctoral researcher Asier Piñeiro Orioli, the lead scientist in the previous research study with Thompson, and also a factor to the two recently released studies, discovered a simple method to comprehend the emergence of a dark state in a cavity in terms of what they called a superradiant potential.Rey elaborates: “We can imagine the superradiant capacity as a roller coaster where atoms ride. As they drop the hill, they produce light collectively, but they can get stuck when they reach a valley. At the valleys, the atoms form the dark states and stop discharging light into the cavity.”In their previous work with Thompson, the JILA researchers found that the dark states must be at least a little bit knotted.”The question we aimed to address in the two brand-new works is whether they can be both dark and highly knotted,” discusses very first author Bhuvanesh Sundar, a previous JILA postdoctoral researcher. “The exciting part is that we not just found that the response is yes, but that these kinds of squeezed states are rather straightforward to prepare.”Creating Highly Entangled Dark StatesIn the brand-new research studies, the researchers found out 2 possible ways to prepare the atoms in extremely knotted spin-squeezed states. One method was by shining the atoms with a laser to energize them above their ground state and after that placing them into special points on the superradiant capacity, likewise called saddle points. At the saddle points, the scientists let atoms relax in the cavity by changing off the laser, and interestingly, the atoms reshape their sound circulation and end up being extremely squeezed.”The saddle points are valleys where the capacity has absolutely no curvature and no slope at the same time,” Rey elaborates. “These are special points since atoms are dark however on the edge of ending up being unsteady and for that reason tend to reshape their sound circulation to ending up being squeezed.”The other proposed method included the transfer of superradiant states into dark states. Here, the group likewise discovered other unique points where the atoms are close to special “intense” points– not in a valley of the roller coaster, however at points with absolutely no curvature– where the interplay between superradiance and an external laser creates spin-squeezing.”The neat thing is that the spin squeezing produced at these brilliant points can then be moved into a dark state where, after proper alignment, we can switch off the laser and protect the squeezing,” Sundar adds.This transfer works by first driving the atoms into a valley of the superradiant potential and then using lasers with appropriate polarizations (or instructions of light oscillations) to coherently align the squeezed instructions, making the squeezed states immune to superradiance.The transfer of squeezed states into dark states not only protected the decreased noise attributes of the squeezed states, but also guaranteed their survival in the absence of being driven by an external laser, an important element for practical applications in quantum metrology.While the research study published in Physical Review Letters utilized just one polarization of the laser light to induce spin squeezing, producing 2 squeezed modes, the Physical Review A paper took this simulation even more by utilizing both polarizations of laser light, leading to 4 spin-squeezed modes (two modes for each polarization).”In these 2 documents, we thought about multilevel atoms with many internal levels,” elaborates Piñeiro Orioli, “and having many internal levels is more difficult to mimic than having two levels, which is frequently studied in the literature. We developed a set of tools to resolve these multilevel systems. We worked out a formula to calculate entanglement created from the preliminary state.”An Improvement to Quantum MetrologyThe findings of these studies can have far-reaching ramifications for atomic clocks. By getting rid of the limitations of superradiance via the generation of dark entangled states, physicists either store the knotted states using the atoms as a memory (enabling for the retrieval of info from these states) or inject the knotted state into a clock or interferometer series for quantum-enhanced measurements.References:”Squeezing Multilevel Atoms in Dark States through Cavity Superradiance” by Bhuvanesh Sundar, Diego Barberena, Ana Maria Rey and Asier Piñeiro Orioli, 17 January 2024, Physical Review Letters.DOI: 10.1103/ PhysRevLett.132.033601″Driven-dissipative four-mode squeezing of multilevel atoms in an optical cavity” by Bhuvanesh Sundar, Diego Barberena, Ana Maria Rey and Asier Piñeiro Orioli, 17 January 2024, Physical Review A.DOI: 10.1103/ PhysRevA.109.013713 This research study was supported by the U.S. Department of Energy, Office of Science, National Quantum Information Science Research Centers Quantum Systems Accelerator, and the National Institute of Standards and Technology (NIST).