21 April 2026 — Day 2
Session 1
| Talk 1: 09:00 – 09:30 |
Exploring the Standard Model with Trapped Exotic Ions |
| Prof Klaus Blaum |
| Max-Planck-Institut für Kernphysik |
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Abstract: The four fundamental interactions and their symmetries, along with the fundamental constants and properties of elementary particles – such as masses and magnetic moments – form the foundational structure of the universe and underpin the well-tested Standard Model (SM) of particle physics. Conducting stringent tests of these interactions and symmetries under extreme conditions, at low energies and with the highest precision, for example by comparing particles and their counterparts, the antiparticles, allows us to probe for potential physics beyond the SM. Advancing these tests beyond their current limits requires the development of innovative experimental techniques. This overview highlights recent technical advancements and measurements of atomic and nuclear masses, as well as 𝑔-factors, with unprecedented precision, performed on individual or a few cooled exotic ions stored in Penning traps. Notably, these experiments have among others enabled the most precise tests of bound-state quantum electrodynamics and have significantly improved the accuracy of several key fundamental constants. |
| Talk 2: 09:30 – 10:00 |
Coherence of local-phonon hopping in a trapped-ion string |
| Prof Kenji Toyoda |
| Osaka University |
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Abstract: Vibrational excitations in trapped ions, or phonons, serve as useful resources for quantum information processing, including quantum simulation and quantum computing. Localized excitations of the vibrational motion of individual ions (local phonons) offer both large information capacity and straightforward scalability, and can be used to simulate quantum particles propagating in a lattice. Hopping of local phonons, described by a hopping Hamiltonian, is an elementary process in such systems, and the coherence of local-phonon hopping is of central importance for applications based on this mechanism. Here we investigate local-phonon hopping and its coherence in the radial direction of a two-ion crystal. We experimentally observe the decay of phonon hopping as a function of the principal trap parameters and compare the results with numerically simulations. In the simulations we incorporate two main effects: residual thermal motion in the axial direction, which affects the dynamics through the nonlinearity of the Coulomb coupling, and electric-potential noise in the trapping environment. Incorporating these effects enables a quantitative comparison between the experimental observation and the numerical results. |
Session 2
| Talk 3: 10:30 – 11:00 |
Structural Transitions and Stochastic Dynamics in Trapped Ion Crystals |
| Prof Sadiq Rangwala |
| Raman Research Institute |
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Abstract: We present a new ion trap experiment, with an end cap type Paul trap built for precision spectroscopy and metrology [1,2]. We will discuss the performance of this experiment and then move quickly to the observation of three dimensional trapped ion crystals of Ca+ ions. The crystals form when the ions attain their configuration of minimum energy (CME) as a result of laser cooling of the ions. As the trap anisotropy is tuned, the crystals deform and structural transitions are seen. We study in detail three distinct structural transitions, all of which break symmetry with a change in the parity-odd octopole order parameter. Our observations show spontaneous symmetry breaking illustrated by a Higgs-like mode, dynamical catastrophe resulting in hysterisis, and stochastic switching [3]. In another experiment we study the thermal activation of the spontaneous inversion of a square pyramid ion crystal, which is aided by permutation symmetry and use this paradigm to test the multidimensional Kramers-Langer theory for reaction rates for the first time [4]. References |
| Talk 4: 11:00 – 11:30 |
Evaluating Excess Micromotion in an Asymmetric Segmented Trap for Ytterbium Optical Clocks |
| Dr Piyaphat Phoonthong |
| National Institute of Metrology (Thailand) |
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Abstract: In this work, we present an evaluation of excess micromotion within a linear, asymmetric segmented Paul trap developed at the National Institute of Metrology, Thailand (NIMT). To characterize the micromotion amplitude, we employ the photon correlation method, which utilizes the correlation between the ion's fluorescence and the trap's RF drive phase to quantify the underlying stray electric field. Following the systematic compensation of these stray fields, we evaluate the resulting frequency shifts on the 435-nm electric-quadrupole clock transition in 171Yb+. Our results demonstrate a second-order Doppler shift contribution of -1.2(8)x10-18, successfully validating both the trap's performance and the effectiveness of our compensation. |
Session 3
| Talk 6: 14:00 – 14:30 |
Validating 176Lu+ Optical Frequency References at the 10−19 level |
| Dr Kyle Arnold |
| Centre for Quantum Technologies, NUS |
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Abstract: The $^{176}\text{Lu}^+$ $^1\text{S}_0 \rightarrow {}^3\text{D}_1$ transition serves as a robust frequency reference due to its low sensitivity to blackbody radiation and electromagnetic perturbations, allowing for high-accuracy operation at room temperature without extensive shielding [1]. Building on recent advances in micromotion control [2], quadrupole shift assessment [3], and studies of background gas collision effects [4], we report a comprehensive evaluation of two independent $^{176}\text{Lu}^+$ single-ion optical frequency references, achieving total systematic uncertainties of $1.1 \times 10^{-19}$ and $1.4 \times 10^{-19}$ [5]. The two systems were directly compared using correlation spectroscopy with Ramsey times of up to 10 seconds, yielding a measurement instability $4.8 \times 10^{-16}(\tau/s)^{-1/2}$. After 200 hours of averaging, the clocks demonstrated a relative frequency agreement of $[-2.4 \pm (5.7)_{\text{stat}} \pm (1.0)_{\text{sys}}] \times 10^{-19}$ [5]. While other individual clocks have reported assessed uncertainties below $10^{-18}$, this work represents the first demonstrated agreement of optical clock performance with total uncertainty below this level. These results open the way for new applications in millimeter-scale relativistic geodesy and tests of fundamental physics at the $10^{-19}$ frontier of accuracy. [2] K. Arnold, N. Jayjong, M. Kang, Q. Qichen, Z. Zhang, Q. Zhao, and M. Barrett, Physical Review A 110, 033115 (2024). [3] M. Lee, Q. Zhao, Q. Qichen, Z. Zhang, N. Jayjong, K. Arnold, and M. Barrett, Physical Review A 113, 012805 (2026). [4] M. Barrett and K. Arnold, arXiv preprint arXiv:2512.05474 (2025). [5] K. Arnold, M. Lee, Z. Qi, Q. Qin, Z. Zhao, N. Jayjong, and M. Barrett, arXiv preprint arXiv:2512.07346 (2025). |
| Talk 7: 14:30 – 15:00 |
Crossing the Reusable Entanglement Threshold over Telecom Fibre in Trapped-Ion Quantum Networks |
| Dr Yong Wan |
| University of Science and Technology of China |
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Abstract: Trapped-ion systems have achieved exceptional performance in local quantum control, with long coherence times and high-fidelity operations routinely demonstrated in single-node processors. Extending these capabilities to long distance networking, however, introduces a fundamental challenge: exponential photon loss in optical fibre suppresses entanglement generation rates, often causing remote entanglement to decay before subsequent links can be established. Restoring balance between entanglement generation and memory coherence in the telecom-loss regime is a central requirement for scalable quantum repeaters. |
| Talk 8: 15:00 – 15:30 |
Hour-scale lifetime and non-equilibrium steady state of trapped ions in an ultracold atom-ion hybrid trap |
| Dr Sourav Dutta |
| Tata Institute of Fundamental Research (TIFR) |
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Abstract: Hybrid atom-ion systems offer unique opportunities for ultracold chemistry, precision measurements, and quantum simulation; but prolonged trapping of non-laser-coolable ions (the vast majority of atomic and molecular species of interest) remains challenging due to rapid losses due to rf heating and background collisions. We demonstrate ion lifetimes more than 80 minutes in a linear Paul trap by cooling ensembles of Cs⁺ ions with ultracold Cs atoms, thus realizing the long-lived regime for ions ensembles that cannot be laser cooled. We report a genuine attracting fixed point in the hybrid system: ion number converges to the same steady state population independent of the initial number of ions. The results open a pathway towards sympathetic cooling of complex species and facilitate studies of rare reactions and driven dissipative systems. |
Evening Session
| Evening Talk: 18:00 – 19:00 |
Helios: A 98-qubit trapped-ion quantum computer |
| Dr. Anthony “Tony” Ransford |
| Quantinuum |
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Abstract: o Helios utilizes hyperfine qubits encoded in 137Ba+ ions and integrates multiple quantum operation regions connected through a junction transport network and rotatable storage ring, enabling flexible ion rearrangement and all-to-all connectivity. o System characterization demonstrates average single-qubit gate fidelity of 2.5(1)×10−5, two-qubit gate fidelity of 7.9(2)×10−4 ,and state-preparation-and-measurement (SPAM) error of 7.9(2)×10−4, maintained across operational zones. These performance levels support deep circuit execution together with mid-circuit measurement and feedforward required for quantum error correction. o Beyond the component level benchmarks, system level benchmarks including mirror benchmarking, binary randomized benchmarking and random circuit sampling are characterized. We show that simulating the results of the random circuit sampling is far beyond the ability of modern supercomputers. o These results demonstrate that the QCCD approach enables simultaneous scaling of qubit number and operational fidelity, establishing a practical pathway toward large-scale fault-tolerant quantum computing with trapped ions. |