LABORATOIRE DE PHYSIQUE ET MODELISATION DES MILIEUX CONDENSES

As a route towards a cluster of interconnected processors in a quantum network, the Quantum Device Lab’s approach to short-range modularity uses small modules with high fabrication yield flip-chip bonded to a common carrier chip. In the first part of this talk, we focus on the hardware realization of this 3D-integrated architecture with indium bump bonds, inter-chip spacing control, and parameter targeting enabling high-fidelity operations [1,2]. We then leverage this technology in a two-module processor, with three qubits per node [3]. The first module acts as a server generating cluster states as entangled quantum resource. The second module acts as a client, consuming the resource through real-time adaptive measurement basis choice. We demonstrate that the client can implement universal single- and two-qubit gates with local measurements and rotations only. As an example of blind quantum computation, we show results of a measurement-based Deutsch-Jozsa algorithm. We verify that the computation remains private, that is, the server’s state doesn’t reveal the client’s algorithm nor its result. This demonstrates that cloud quantum providers can be set up in a way that they respect the data privacy of their clients [4].

[1] Norris et al., EPJ Quant. Tech. 11, 5 (2024)
[2] Norris et al., EPJ Quant. Tech. 13, 29 (2026)
[3] Dalton et al., PRX Quantum 6, 040365 (2025)
[4] Song et al., arXiv:2605.14656 (2026)

In this work, we propose a scalable Liouvillian (Hamiltonian and dissipation) measurement protocol for quantum computers. We will show both numerical and experimental results on 1D chains of 10 and 51 of trapped ions, subject to XY power-law interactions [1].

A generic characterization protocol for the Liouvillian, that does not rely on strong assumptions about its form, is crucial in quantum simulation experiments. It can be used to verify that the target model have been approximately implemented, and to identify the unwanted generated terms (and so possibly correct them).

Using randomized state preparation and measurement, we show that all two-body Hamiltonian terms and single-body dissipative terms can be learnt in a pairwise manner [2]. As a result, the classical memory required by the protocol remains independent of the system size, making the method scalable to large quantum simulators.

References:
[1] Bounded-Error Quantum Simulation, T.Kraft et al, https://arxiv.org/abs/2511.23392v1
[2] Pairwise Liouvillian learning, W.T.Lam et al, 2026, https://arxiv.org/abs/2605.26953

The motion of a single hole in a two-dimensional antiferromagnet can lead to the formation of a low-energy quasiparticle, a so-called spin-polaron, which amounts to a bound state of the doped hole and a spin flip. In this talk, I will first introduce the notion of spin-polarons and then discuss spectroscopic signatures of this quasiparticle at the example of two different material classes which both host quasi two-dimensional low-energy physics in their correlated electronic structure.
Illustrated by the Na-doped oxychloride Ca2CuO2Cl2, we will see how the spin-polaron gives rise to “kink” and “waterfall” features in the spectral function of hole-doped cuprates. Employing a numerical workflow comprising density functional theory and cluster dynamical mean-field theory, we will discuss these features in comparison to measurements obtained from angle-resolved photoemission spectroscopy. As a second example, we will see that spin-polaron physics is also relevant in two prototypical iridates, (Ba,Sr)2IrO4, which host an exotic spin-orbital entangled jeff=1/2 ground state. In particular, the characteristic two-peak structure of their optical absorption and optical conductivity curves will be revisited and interpreted in the light of these coherent low-energy quasiparticles.

B. Bacq-Labreuil et al., Phys. Rev. Lett. 134, 016502 (2025)
F. Cassol et al., arXiv:2509.20337; accepted in Phys. Rev. B (2026)

Trapped ions are among the most promising paths to realizing quantum computers, having exhibited the highest fidelity gates and long coherence times. Scaling up will require the adoption of new technologies, and can be facilitated by new approaches. In this talk I will describe recent work from our group in both directions. Firstly I will describe the use of integrated optics to deliver light to multiple zones of an ion trap chip in scalable manner, and give an impression of the new types of control which might be enabled by this approach [1,2,3]. I will then introduce a new concept for scaling trapped-ion quantum computers based on microfabricated Penning traps, introducing flexible 2-dimensional ion transport while removing the need for high-voltage radio-frequency fields and thus improving compatibility with standardized chip fabrication [4,5]. We have used this to perform sensing of both static and oscillating magnetic and electric fields near the chip surface, and more recently demonstrated multi-qubit gates and control of multi-dimensional arrays of ions.

[1] K. Mehta et al. Nature 586, 533–537 (2018)

[2] A. Ricci et al. Phys. Rev. Lett. 130, 133201 (2023)

[3] C. Mordini et al. Physical Review X 15, 011040 (2025)

[4] S. Jain et al. Physical Review X 10, 031027 (2021)

[5] S. Jain et al. Nature 627, 8004, pp. 510–514 (2024)