Monolithic ion trap integration of superconducting nanowire single-photon detectors and photonics for trapped-ion qubit state readout

Atomic ions can be trapped in vacuum with dc and rf electric potentials generated by surface electrode ion traps, and used as qubits in quantum computing applications. Qubit state preparation and control is usually accomplished with laser light while the qubit state readout is achieved by observing qubit-state-dependent fluorescence from the ion while driving an optical cycling transition. The monolithic integration of optical waveguides and single-photon detectors into the ion trap itself provides both light delivery and fluorescence photon counting capability, offering benefits for scaling in trapped ion quantum computing by eliminating the need for free-space optical access to the trap. One promising candidate for integrated high-fidelity trapped-ion qubit state readout are superconducting nanowire single-photon detectors (SNSPDs). However, the joint integration of photonics and superconducting detectors into ion trap chips presents challenges for their design, fabrication, and operation. In this work, we present our progress on the integration of SNSPDs into linear ion traps with integrated photonics designed for Ca+ qubits.