Polaritons and Entanglement in Ultracold Sodium Gases

About This Grant

When a gas is cooled to ultracold temperatures, the atoms stop behaving as single particles. Instead, the atoms form a single object known as matter wave, governed by the fascinating laws of quantum mechanics. In the matter wave collisions happen in lockstep. The magnetic orientations of atomic pairs become strongly correlated after each collision, and they become quantum-mechanically entangled. The quantum-entangled atoms react to external influences in unison. Compared to traditional antennas, atomic sensors have several advantages. They have a higher resolution because they are microscopic in size, they are self-calibrating because the atoms are identical to each other, and their response can have an improved signal-to-noise ratio because of quantum entanglement. The PI and graduate students will study new atomic sensing protocols to learn how quantum entanglement can be controlled in a robust way, even in the presence of significant detection noise. The PI and graduate students will also investigate the role of impurities in sensing with ultracold gases. The award supports two graduate students who will work together to complete the project. Undergraduate students will participate via senior thesis and summer research projects. By training STEM workers in this region, the PI will contribute to increasing the high-tech workforce in Oklahoma. The PI will offer four interactive summer mini-lectures per year on ultracold gases. For outreach, the PI will hold one public event each year with demonstrations and lab tours, working with the local Engineering Days program for high school students. The PI and graduate students will leverage a robust prototyping platform for matter-wave quantum technologies to study polarons and entanglement generation in ultracold sodium gases. Control of entanglement generation is exerted by microwave-dressing, RF fields, and magnetic field control of spin-exchange collisions in a Bose-Einstein condensate of atomic sodium. Working in a regime of large populations of entangled pairs, far away from resonance, as well as using a beam-splitter operation during interferometry, will make quantum-enhanced sensing more robust to detection noise. Based on progress made and insights gained over the last funding period, the research team will a) study quantum-enhanced sensing via new protocols of spin-mixing interferometry that are robust to detection noise and make use of massive entanglement in the system, and b) study Rydberg polaron excitations as a simulation of impurities. This project will demonstrate that matter-wave based quantum technologies can show advantageous metrological gains beyond the standard quantum limit even in the presence of realistic effects such as detection noise, decoherence, and the presence of impurities. The research team will develop a toolbox based on microwave-dressing and rf-pulse sequences that operate on atoms, analogous to how quantum optics devices such as four-wave mixing cells and beamsplitters operate on photons. This will unlock powerful techniques, known from quantum optics, for use on ultracold gases. The project has significance for condensed matter physics, because the excitation of polarons in the atomic gas, via Rydberg excitations, will emulate impurities in solid-state systems. However, in contrast to solid state devices, the experiments with ultracold sodium gases will allow control at the level of single impurities. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.