JILA Science Seminar

Continuous-variable quantum systems enable encoding complex states in fewer modes through large-scale non-Gaussian states. Motion, as a continuous degree of freedom, underlies phenomena from Cooper pair dynamics to levitated macroscopic objects. Hence, realizing high-energy, spatially extended motional states remains key for advancing quantum sensing, simulation, and foundational tests.
In the talk, I will present the following control tasks for various nonlinear mechanical systems, including trapped atoms, levitated particles, and clamped oscillators with spin-motion coupling.

Rydberg atoms in optical tweezers have become a leading platform for both quantum simulation and quantum computing. However, they are often limited by their relatively short lifetime of a few tens of microseconds. One way to overcome this limitation is to use Rydberg atoms with maximum angular momentum (m = l = n-1), known as circular states. When placed in a cryogenic environment, these states can exhibit lifetimes of several milliseconds. Circular states of alkaline-earth-like atoms offer additional advantages.

Nuclear spins are usually not thought to participate in chemical reactions. However, in the ultracold temperature regime, we have a new opportunity to examine this general statement with quantum mechanical details. In this talk, I will present our ongoing investigations into the roles of nuclear spins, quantum coherence, and entanglement in molecule-molecule reactions and atom-molecule collisions, utilizing a one-of-a-kind ultracold KRb molecule apparatus inspired from the original set of JILA KRb experiments 17 years ago.

The promise of universal quantum computing hinges on scalable single- and inter-qubit control interactions. Photon systems offer strong isolation from environmental disturbances and provide speed and timing advantages while facing challenges in achieving deterministic photon-photon interactions necessary for scalable universal quantum computing.

The behavior of the doped Hubbard model at low temperatures is a central problem in modern condensed matter physics, with relevance to correlated materials such as cuprate superconductors. Despite extensive computational studies, many open questions remain on its low-temperature phase diagram, motivating its study through quantum simulation with ultracold fermionic atoms in optical lattices. Here, leveraging a recent several-fold reduction in experimental temperatures, we report the first direct experimental observation of the pseudogap metal in the Hubbard model.

Continuous-wave (CW) interferometers and oscillators lie at the core of many modern precision measurements including atomic clocks and ground and space based gravitational wave detectors. As with all measurements, quantum mechanics sets the ultimate limit on the precision of these devices. In interferometers employing only classical sources of light, such as thermal sources and lasers, sensitivity is bounded by “standard quantum limit” (SQL) scaling.

Abstract: Fault-tolerant quantum computation requires further advances in lowering physical qubit error rates in scalable architectures. In this talk, I will present our work on superconducting quantum devices to reduce error rates and resource overheads in processors.  I will discuss how defects and interfaces in silicon limit superconducting qubit performance. I will present our discovery of interface piezoelectricity at a superconductor-silicon junction and the impact of this effect on superconducting qubits.

Abstract: Engineered quantum systems, encompassing artificial mesoscopic structures governed by the principles of quantum mechanics, represent a cornerstone of modern quantum science. Notable examples include superconducting circuits, ultracold trapped atoms and ions, as well as electro and optomechanical systems. These systems are not only fascinating from a fundamental physics perspective but also serve as essential building blocks for technological applications.

Many-body localization (MBL) is a many-body quantum phenomenon that fails to thermalize under strong disorder. While experimental work on optical lattice systems suggests the existence of a MBL phase in 2D, there have been challenges regarding its existence in two dimensions. The main challenge of MBL in higher dimensions is an avalanche instability: rare regions of weak disorder can act as a thermal bath, which eventually thermalizes the entire system.

Abstract: Quantum processors have the potential to significantly advance our understanding of quantum systems. In particular, the programmability of digital quantum devices can enable access to highly tunable quantum dynamics and observables. The central challenge, however, is suppressing errors, making quantum error correction essential for large-scale algorithms.