Publications Teresa HÖNIGL-DECRINIS

2025

D. Atanasova, I. Yang, T. Hönigl-Decrinis, D. Gusenkova, I. M. Pop, G. Kirchmair In-situ tunable interaction with an invertible sign between a fluxonium and a post cavity, PRX Quantum 6 20318 (2025-04-25), http://dx.doi.org/10.1103/PRXQuantum.6.020318 doi:10.1103/PRXQuantum.6.020318 (ID: 721273) Toggle Abstract
Quantum computation with bosonic modes presents a powerful paradigm for harnessing the principles of quantum mechanics to perform complex information processing tasks. In constructing a bosonic qubit with superconducting circuits, nonlinearity is typically introduced to a cavity mode through an ancillary two-level qubit. However, the ancilla's spurious heating has impeded progress towards fully fault-tolerant bosonic qubits. The ability to in situ decouple the ancilla when not in use would be beneficial but has so far only been realized with tunable couplers or additional parametric drives. This work presents a novel architecture for quantum information processing, comprising a 3D post cavity coupled to a fluxonium ancilla via a readout resonator. This system's intricate energy level structure results in a complex landscape of interactions whose sign can be tuned in situ by the magnetic field threading the fluxonium loop without the need of additional elements. Our results could significantly advance the lifetime and controllability of bosonic qubits.

R. Holzinger, R. Gutierrez Jauregui, T. Hönigl-Decrinis, G. Kirchmair, A. Asenjo Garcia, Helmut Ritsch Control of Localized Single- and Many-Body Dark States in Waveguide QED, Phys. Rev. Lett. 129 (2022-12-14), http://dx.doi.org/10.1103/PhysRevLett.129.253601 doi:10.1103/PhysRevLett.129.253601 (ID: 720918) Toggle Abstract
Subradiant states in a finite chain of two-level quantum emitters coupled to a one-dimensional reservoir are a resource for superior photon storage and their controlled release. As one can maximally store one energy quantum per emitter, storing multiple excitations requires delocalized states, which typically exhibit fermionic correlations and antisymmetric wave functions, thus making them hard to access experimentally. Here we identify a new class of quasilocalized dark states with up to half of the qubits excited, which only appear for lattice constants of an integer multiple of the wavelength. These states allow for a high-fidelity preparation and minimally invasive readout in state-of-the-art setups. In particular, we suggest an experimental implementation using a coplanar waveguide coupled to superconducting transmon qubits on a chip. With minimal free space and intrinsic losses, virtually perfect dark states can be achieved for a low number of qubits featuring fast preparation and precise manipulation.