Trapped ion fluorescence detection at room temperature enhances quantum scalability

A rapidly evolving field, quantum technology boasts promising applications in computing and simulation, networking, sensing, and precision timekeeping. Quantum information can be stored in trapped ions, or qubits, and then “read out” by detecting the photons they fluoresce.

One of the primary challenges in developing quantum devices is the ability to scale up the number of qubits in ion trap systems, which requires optically addressing and detecting large numbers of qubits.

Setzer et al. present the first demonstration of trapped ion fluorescence detection using complementary metal–oxide–semiconductor (CMOS)-compatible, surface-trap-integrated single photon avalanche photodiode (APD) detectors. Monolithically integrated with a microfabricated surface ion trap, the photodetectors are designed to detect 370-nanometer photons emitted from each ion.

“The results are promising, with good detector quantum efficiency and low dark counts at room temperature,” said author William Setzer. “So far, we can distinguish the presence of a single fluorescing ion with 99% accuracy in 7.7 milliseconds.”

While room temperature fluorescence detection with trap integrated APDs was previously proposed, this work represents the first to showcase it. This demonstration has major implications for transportable quantum systems, since room-temperature, surface-trap-integrated APD detectors do not require large, heavy, power-hungry, and expensive cryostats to operate, nor bulk free space optics as do conventional free space imaging systems.

“This technology enables state detection for scalable and transportable quantum systems, shrinking what was previously a centimeter scale imaging system by a factor of 10,000 to a micron-scale, on-chip detector,” said Setzer. “Multiple detectors can be fabricated on the chip’s surface allowing for the ability to perform state detection on many ions.”

Source: “Fluorescence detection of a trapped ion with a monolithically integrated single-photon-counting avalanche diode,” by W. J. Setzer, M. Ivory, O. Slobodyan, J. W. Van Der Wall, L. P. Parazzoli, D. Stick, M. Gehl, M. G. Blain, R. R. Kay, and H. J. McGuinness, Applied Physics Letters (2021). The article can be accessed at https://doi.org/10.1063/5.0055999 .