LPHYS'26
34th Annual International Laser Physics Conference

Spin-Selective Coherent Light Scattering from Ion Crystals and Towards Scalable Quantum Computing

F Schmidt-Kaler1

1 QUANTUM, Institut für Physik, University of Mainz, Mainz, Germany

Seminar: Pl — Plenary Session

Tuesday, 7 July 2026 · 10:50 – 11:30

Abstract

Figure 1

Fig. 1. Left: Linear crystal of 6 ions observed in the far field and featuring interference fringes. Right: Trap chip for quantum computing fabricated by selective laser etching

We are fascinated by the intriguing features of quantum light. Thus, we study collective light scattering off a linear crystal of 40Ca+ ions, each ion acting as a coherent single photon emitter. The scattered intensity is recorded in the far field, featuring the interference of emitted light [1-4]. Furthermore, we demonstrate spin-dependent scattering and unveil the time evolution of a previously encoded spin texture [5]. In future, we plan to detect projectively generated entanglement in larger ion crystals.

This research is closely connected with the challenges on the way to scalable quantum computers with trapped ion qubits, and I will describe these challenges on the way to scalable, eventually fault tolerant quantum computers [6]. Efforts from physics, informatics [7,8] and mathematics, but also engineering [9], are concentrated in demonstrator setups. As a first glance into the power of quantum computing, I will describe a couple of use cases. This includes the VQE simulation of a two-flavor Schwinger quark model executed on a trapped-ion quantum processor [10], and, by extending the toolset of quantum operations, the investigation of circuits that realize quantum thermodynamic processes [11-13].

References

  1. F Schmidt-Kaler and J von Zanthier, Collective Light emission of ion crystals in correlated Dicke states, in: M Benyoucef (ed.), Photonic Quantum Technologies - Science and Applications, ISBN: 978-3-527-41412-3, Wiley-VCH, Berlin (2023)
  2. S Richter, S Wolf, J von Zanthier and F Schmidt-Kaler, Phys. Rev. Res. 5, 013163 (2023); DOI: 10.1103/PhysRevResearch.5.013163
  3. S Richter, S Wolf, J von Zanthier and F Schmidt-Kaler, Phys. Rev. Lett. 126, 173602 (2021); DOI: 10.1103/PhysRevLett.126.173602
  4. S Wolf, S Richter, J von Zanthier and F Schmidt-Kaler, Phys. Rev. Lett. 124, 063603 (2020); DOI: 10.1103/PhysRevLett.124.063603
  5. M Verde, A Schaefer, B Zenz, et al., Phys. Rev. A 112, 043719 (2025); DOI: 10.1103/7bd7-4trn
  6. J Hilder, D Pijn, O Onishchenko, et al., Phys. Rev. X 12, 011032 (2022); DOI: 10.1103/PhysRevX.12.011032
  7. F Kreppel, C Melzer, D Olvera Millán, et al., Quantum 7, 1176 (2023); DOI: 10.22331/q-2023-11-08-1176
  8. J Durandeau, J Wagner, F Mailhot, et al., Quantum 7, 1175 (2023); DOI: 10.22331/q-2023-11-08-1175
  9. V Kaushal, B Lekitsch, A Stahl, et al., AVS Quantum Sci. 2, 014101 (2020); DOI: 10.1116/1.5126186
  10. C Melzer, S Schuster, D A Olvera Millán, et al., arXiv: 2504.20824 (2025)
  11. E J Fox, M Herrera, F Schmidt-Kaler and I D’Amico, Entropy 26, 952 (2024); DOI: 10.3390/e26110952
  12. O Onishchenko, G Guarnieri, P Rosillo-Rodes, et al., Nat. Commun. 15, 6974 (2024); DOI: 10.1038/s41467-024-51263-3
  13. A Stahl, M Kewming, J Goold, et al., arXiv: 2404.14838 (2024)
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