Zhenyu Wei

Trapped ions are a leading technology for quantum computing, but their reliance on bespoke tabletop laser and optical systems remains a major obstacle to scaling and robustness. Integrated silicon nitride lasers, compatible with future monolithic integration with surface electrode ion traps, have recently demonstrated frequency-selective qubit state preparation and measurement as well as interrogation of an optical clock transition. However, coherent qubit gates driven by integrated laser sources have not yet been demonstrated because coherent quantum logic imposes substantially more stringent performance requirements on the laser. Here, we use a visible-wavelength integrated Brillouin laser stabilized to an integrated coil resonator to drive coherent single- and two-qubit gates with $^{88}$Sr$^+$ optical qubits. We measure an average single-qubit fidelity of 99.61% $\pm$ 0.03% per Clifford gate with randomized benchmarking and use a two-qubit Mølmer-Sørensen interaction to generate an entangled Bell state with a fidelity of 92.35% $\pm$ 1.50%. The qubit exhibits a bare Ramsey coherence time of 660 $\pm$ 9 $μ$s, extended to 1.750 $\pm$ 0.033 ms by spin echo. These results demonstrate that integrated visible-wavelength narrow-linewidth photonic lasers can meet the phase-noise requirements for coherent trapped ion quantum logic, providing a path for scalable optical systems integrated within trapped ion quantum processors.

Complex optical design is hindered by conventional piecewise setup, which prevents modularization and therefore abstraction of subsystems at the circuit level. This limits multiple fields that require complex optics systems, including quantum computing with atoms and trapped ions, because their optical systems are not scalable. We present an open-source Python library for optical layout (PyOpticL) which uses beam-path simulation and dynamic beam-path routing for quick and easy optical layout by placing optical elements along the beam path without a priori specification, enabling adaptive, path-based layouts with automatic routing and connectivity. We use PyOpticL to create modular `drop-in' optical baseplates for common optical subsystems used in atomic and molecular optics (AMO) experiments including laser sources, frequency and intensity modulation, and locking to an atomic reference for stabilization. We demonstrate this minimal working example of a dynamic full laser system for strontium trapped ions by using it for laser cooling, qubit state detection, and over 99% fidelity single-qubit gates with 3D printed baseplates. This enables a new paradigm of design abstraction layers for engineering optical systems leveraging modular baseplates, as they can be used for any wavelength in the system and enables scaling up the underlying optical systems for quantum computers. This new open-source hardware and software code-to-CAD library seeks to foster open-source collaborative hardware and systems design across numerous fields of research including AMO physics and quantum computing with neutral atoms and trapped ions.