Monolithic integration of control technologies for atomic systems is a promising route to the development of quantum computers and portable quantum sensors1,2,3,4. Trapped atomic ions form the basis of high-fidelity quantum information processors5,6 and high-accuracy optical clocks7. However, current implementations rely on free-space optics for ion control, which limits their portability and scalability. Here we demonstrate a surface-electrode ion-trap chip8,9 using integrated waveguides and grating couplers, which delivers all the wavelengths of light required for ionization, cooling, coherent operations and quantum state preparation and detection of Sr+ qubits. Laser light from violet to infrared is coupled onto the chip via an optical-fibre array, creating an inherently stable optical path, which we use to demonstrate qubit coherence that is resilient to platform vibrations. This demonstration of CMOS-compatible integrated photonic surface-trap fabrication, robust packaging and enhanced qubit coherence is a key advance in the development of portable trapped-ion quantum sensors and clocks, providing a way towards the complete, individual control of larger numbers of ions in quantum information processing systems.
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We thank P. Murphy, C. Thoummaraj and K. Magoon for assistance with chip packaging, and P. Hassett and K. Yu for chip-facet polishing. This material is based on work supported by the Department of Defense under Air Force Contract number FA8702-15-D-0001. Any opinions, findings, conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the Department of Defense.
The authors declare no competing interests.
Peer review information Nature thanks Jungsang Kim and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Extended data figures and tables
Extended Data Fig. 1 Plan view of one of the grating couplers superimposed on the trap electrode metal (partial).
The single-mode (SM) waveguide is tapered to provide a wider beam at the grating coupler. The grating teeth are formed via a partial etch into the waveguide material beneath a window in the electrode metal. The gratings used are forward-emitting, designed to emit a beam to the ion location as depicted, but 55 μm above the surface of the metal.
a, High-numerical-aperture microscope images of the beams are taken while vertically scanning the focal plane above the chip. b, c, Laser light is emitted from the grating couplers and imaged at a height of z = 0 (b) and z = 25 μm (c) above the ion-trap electrodes.
Extended Data Fig. 3 Ion interaction profile of 408-nm light, which was used as a proxy for 405-nm light.
Error bars indicate the standard error of the mean.
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Niffenegger, R.J., Stuart, J., Sorace-Agaskar, C. et al. Integrated multi-wavelength control of an ion qubit. Nature 586, 538–542 (2020). https://doi.org/10.1038/s41586-020-2811-x
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