Laboratory of Hybrid Quantum Circuits

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Controlling Atom-Photon Bound States in an Array of Josephson-Junction Resonators

Pasquale Scarlino

Engineering the electromagnetic environment of a quantum emitter gives rise to a plethora of exotic light -matter interactions. In particular, photonic lattices can seed long-lived atom-photon bound states inside photonic band gaps. Here, we report on the concept and implementation of a novel microwave architecture consisting of an array of compact superconducting resonators in which we have embedded two frequency -tunable artificial atoms. We study the atom-field interaction and access previously unexplored coupling regimes, in both the single-and double-excitation subspace. In addition, we demonstrate coherent interactions between two atom-photon bound states, in both resonant and dispersive regimes, that are suitable for the implementation of SWAP and CZ two-qubit gates. The presented architecture holds promise for quantum simulation with tunable-range interactions and photon transport experiments in the nonlinear regime.

AMER PHYSICAL SOC2022

Fully Tunable Longitudinal Spin-Photon Interactions in Si and Ge Quantum Dots

Pasquale Scarlino

Spin qubits in silicon and germanium quantum dots are promising platforms for quantum computing, but entangling spin qubits over micrometer distances remains a critical challenge. Current prototypical architectures maximize transversal interactions between qubits and microwave resonators, where the spin state is flipped by nearly resonant photons. However, these interactions cause backaction on the qubit that yields unavoidable residual qubit-qubit couplings and significantly affects the gate fidelity. Strikingly, residual couplings vanish when spin-photon interactions are longitudinal and photons couple to the phase of the qubit. We show that large and tunable spin-photon interactions emerge naturally in state-of-the-art hole spin qubits and that they change from transversal to longitudinal depending on the magnetic field direction. We propose ways to electrically control and measure these interactions, as well as realistic protocols to implement fast high-fidelity two-qubit entangling gates. These protocols work also at high temperatures, paving the way toward the implementation of large-scale quantum processors.

AMER PHYSICAL SOC2022

System and method for removing scalloping and tapering effects in high aspect ratio through-silicon vias of wafers

Sandro Carrara, Edoardo Charbon, Simone Frasca

A method for manufacturing vias in a silicon wafer, the silicon wafer having a crystal orientation, and having a plane that is perpendicular to a surface of the wafer, tilted by 35.26°, the method comprising the steps of providing a mask having a rhomboidal-shaped opening onto a surface of the silicon wafer, such that edges of the rhomboidal-shaped opening line up with a plane of a crystalline structure of the silicon wafer, etching a hole in the silicon wafer at the rhomboidal-shaped opening, and polishing the hole after the etching by a anisotropic etching.

2021