Advancing the frontiers of quantum science and engineering

Abstract: The design of a high optical access cryogenic system for Rydberg atom arrays is discussed. Technical challenges around thermal/acoustic isolation and vacuum are also presented. The trap lifetime is measured to be 3000s and the Rydberg coherence is characterized. Next, a quantum many-body simulator employing a cavity-coupled BEC is presented. Interactions between atoms are mediated by scattering into the cavity mode which leads to a quantum phase transition at zero temperature. Steps to engineer atom-atom interactions that are fully tuneable in range, shape, and sign are then presented along with a proof of concept test in one dimension.

Abstract: Classical cryptography, which often involves pre-shared secret keys, is vulnerable to malicious parties who employ various methodologies to gain unauthorized access to the keys, underlying the safety of our network. Quantum cryptography, such as Quantum Key Distribution (QKD), leverages the no-cloning property of quantum mechanics to improve the security level without the need for pre-distributed secret keys. Extending beyond secret keys sharing, special relativity can also be incorporated to authenticate the geographical location of the node within the network, a method called Quantum Position Verification (QPV). In this talk, I focus on the development of hardware platforms specifically designed for free-space photon-polarization realization of QPV at Harvey Mudd College. Our objective is to provide a proof-of-concept demonstration of a QPV network operating over a kilometer range. The proposed demonstration includes two verifier nodes and one prover node, the position of which is verified using QPV. We utilize a free-space polarization photonic qubit link, accompanied with wavelength-multiplexed classical communication pathways, to perform BB84-type transactions. In addition, we employ the Xilinx Zynq FPGA platform to control and maintain the timing of these transactions to verify the prover node’s position relative to each verifier node. Our photon source has demonstrated a qubit polarization basis transition in under 20 ns, while the classical communication link has achieved a bit-error-rate below one-in-a-million at 10 MHz over a 10-meter separation. We are currently working on refining the polarization qubit generation and measurement methodologies to obtain a higher fidelity BB84-type qubit. At the same time, we are extending the range of our classical link moving closer to the kilometer range while examining potential higher data transmission speeds up to 25 MHz.

Abstract: Quantum error correction offers a path to practical quantum computing by combining multiple physical qubits into a single logical qubit. The central promise of this approach relies on the "threshold theorem": if physical error rates can be reduced below a critical threshold value, increasing the number of physical qubits (the code distance) should result in an exponential suppression of the logical error rate. In this talk, I will describe the first experimental demonstration of this foundational principle using Willow, a new generation of superconducting quantum processors from Google Quantum AI. As we scale the surface code from distance 3 to 7, the logical error rate is exponentially suppressed, culminating in a logical memory that persists longer than the coherence time of all constituent physical qubits. I will also discuss the engineering challenges required to achieve this performance. More information about this work can be found in Nature 638, 920–926 (2025).

ACTI will bring together the growing community of ion-trappers from Asia and across the globe. As an inaugural conference, this year will highlight various scientific fields covered by trapped ion research within Asia and facilitate meaningful exchange between junior and senior members of the different groups.

The goal of this workshop is to bring the active research community together to discuss the progress, challenges and new possible directions for quantum repeaters and networks. We invite researchers working on key enabling technologies and system integration, protocols for connecting repeaters across network links with high fidelity, architectures for large-scale networks, and applications of distributed quantum entanglement. The WQRN has been and continues to be a limited-attendance, few-day workshop, in which participants are given the opportunity to share ideas, directions, and concerns to advance the state of the field. Talks are by invitation only and catered to broadly cover the applications, theory, components, and worldwide directions in quantum repeaters and networks. These talks frame group discussion sessions for which all participants are welcome to contribute; participants are also welcome to contribute to a poster session.