Continuous variable quantum computing
An alternative approach to discrete quantum bits is to use a large number of states of a harmonic oscillator to encode the values 0 and 1 of a logical qubit into complex superpositions of harmonic states. This approach is referred to as continuous-variable quantum computing. We explore continuous variable quantum computing in 3d- and planar microwave resonators. Our superconducting 3d cavities provide state-of-the-art quality factors and long-living photon states allowing us to encode quantum information in multi-photon states. This makes it possible to implement hardware-efficient quantum error correction while keeping the noise channels limited. We are currently actively investigating these directions.
Quantum process tomography of continuous-variable gates using coherent states
M. Kervinen, S. Ahmed, M. Kudra, A. Eriksson, F. Quijandría, A. F. Kockum, P. Delsing, and S. Gasparinetti, Quantum Process Tomography of Continuous-Variable Gates Using Coherent States, arXiv:2303.01451.
Experimental realization of deterministic and selective photon addition in a bosonic mode assisted by an ancillary qubit
M. Kudra, T. Abad, M. Kervinen, A. M. Eriksson, F. Quijandría, P. Delsing, and S. Gasparinetti, Experimental Realization of Deterministic and Selective Photon Addition in a Bosonic Mode Assisted by an Ancillary Qubit, arXiv:2212.12079.
Robust preparation of Wigner-negative states with optimized SNAP-displacement sequences
M. Kudra, M. Kervinen, I. Strandberg, S. Ahmed, M. Scigliuzzo, A. Osman, D. Pérez Lozano, G. Ferrini, J. Bylander, A. Frisk Kockum, F. Quijandría, P. Delsing, and S. Gasparinetti, Robust preparation of Wigner-negative states with optimized SNAP-displacement sequences, PRX Quantum 3, 030301 (2022) (Editors’ Suggestion)
Propagating Wigner-negative states generated from the steady-state emission of a superconducting qubit
Y. Lu, I. Strandberg, F. Quijandría, G. Johansson, S. Gasparinetti, and P. Delsing, Propagating Wigner-Negative States Generated from the Steady-State Emission of a Superconducting Qubit, Phys. Rev. Lett. 126, 253602 (2021).
Universal Gate Set for Continuous-Variable Quantum Computation with Microwave Circuits
T. Hillmann, F. Quijandriá, G. Johansson, A. Ferraro, S. Gasparinetti, and G. Ferrini, Universal Gate Set for Continuous-Variable Quantum Computation with Microwave Circuits, Physical Review Letters 125, (2020).
High quality three-dimensional aluminum microwave cavities
M. Kudra, J. Biznárová, A. Fadavi Roudsari, J. J. Burnett, D. Niepce, S. Gasparinetti, B. Wickman, and P. Delsing, High Quality Three-Dimensional Aluminum Microwave Cavities, Applied Physics Letters 117, 070601 (2020). (Editor’s Pick)