[Paper Review] Integrated optical control and enhanced coherence of ion qubits via multi-wavelength photonics

Robert Niffenegger, Jules Stuart+10 more|arXiv (Cornell University)|Jan 14, 2020

Advanced Fiber Laser Technologies4 citations

TL;DR

This paper demonstrates a CMOS-compatible, monolithically integrated photonic chip that delivers multiple laser wavelengths—spanning violet to infrared—directly to a surface-electrode ion trap for full control of Sr⁺ ion qubits. By using integrated waveguides and grating couplers to route light via an optical-fiber array, the system achieves vibration-resilient qubit coherence, enabling a stable, portable platform for trapped-ion quantum technologies.

ABSTRACT

Monolithic integration of control technologies for atomic systems presents a promising route to the development of quantum computers and portable quantum sensors. Trapped atomic ions form the basis of high-fidelity quantum information processors and high-accuracy optical clocks, but currently rely on free-space optics for ion control, limiting portability and scalability. Here we demonstrate a surface-electrode ion trap which delivers all wavelengths required for ionization, cooling, coherent operations, and quantum-state preparation and detection of Sr$^{+}$ qubits using integrated waveguides and grating couplers. Laser light from the violet to the infrared is coupled onto the chip via an optical-fiber array, creating an inherently stable optical path that we use to demonstrate qubit coherence resilient to platform vibrations. This demonstration of CMOS-compatible integrated-photonic surface-trap fabrication, robust packaging, and enhanced qubit coherence represents a key advance in the development of portable trapped-ion quantum sensors and clocks, and it lights the way toward the complete, individual control of larger numbers of ions in quantum information processing systems.

Motivation & Objective

• To overcome the limitations of free-space optics in trapped-ion quantum systems by enabling monolithic photonic integration for scalable, portable quantum technologies.
• To develop a CMOS-compatible platform that delivers all required laser wavelengths—ionization, cooling, coherent operations, and state detection—directly to a surface-electrode ion trap.
• To enhance qubit coherence by eliminating mechanical instability from bulk optical components through a fiber-coupled, on-chip optical path.
• To demonstrate robust packaging and stable operation of integrated photonic components in a quantum control platform suitable for real-world deployment.

Proposed method

• The system uses a monolithically integrated photonic chip with waveguides and grating couplers to route laser light from the violet to infrared spectrum onto the ion trap.
• An optical-fiber array is used to couple laser light from external sources into the chip, creating a stable, fixed optical path that minimizes mechanical drift.
• The photonic chip is fabricated using CMOS-compatible processes, enabling scalability and integration with existing semiconductor technology.
• Laser wavelengths are precisely directed to the ion trap for ionization, sideband cooling, Raman transitions, and state readout using on-chip components.
• The entire system is packaged to protect the photonic components and maintain alignment under environmental disturbances such as vibrations.
• Qubit coherence is measured under platform vibrations to assess stability, with results compared to conventional free-space setups.

Experimental results

Research questions

• RQ1 Can a monolithically integrated photonic chip deliver all required laser wavelengths for full control of Sr⁺ ion qubits in a single, compact platform?
• RQ2 How does the stability of the on-chip optical path compare to free-space optics in terms of qubit coherence under mechanical vibrations?
• RQ3 To what extent can CMOS-compatible fabrication enable scalable and portable trapped-ion quantum systems?
• RQ4 Can robust packaging preserve the performance of integrated photonic components in a functional ion-trap environment?

Key findings

• The integrated photonic chip successfully delivers laser light across the violet to infrared spectrum required for ion control, including ionization, cooling, and state detection.
• Qubit coherence is preserved under platform vibrations due to the inherently stable, fiber-coupled optical path, demonstrating resilience to mechanical disturbances.
• The system achieves full control of Sr⁺ ion qubits using a single, monolithic photonic platform, eliminating the need for bulk optics.
• CMOS-compatible fabrication enables scalable integration of photonic components with surface-electrode ion traps, paving the way for larger-scale quantum processors.
• Robust packaging maintains alignment and performance of the photonic components, supporting real-world deployment of portable quantum sensors and clocks.
• The demonstrated platform provides a stable, compact, and scalable solution for future trapped-ion quantum information processing and sensing.