State Readout of a Trapped Ion Qubit Using a Trap-Integrated Superconducting Photon Detector

Area of Science:

• Quantum Information Science
• Atomic Physics
• Solid-State Physics

Background:

• Trapped ion qubits are promising for quantum computing.
• Efficient and high-fidelity state readout is crucial for quantum computation.
• Integrating photon detectors directly into ion traps presents engineering challenges.

Purpose of the Study:

• To demonstrate high-fidelity state readout of a trapped ion qubit.
• To utilize a trap-integrated superconducting nanowire single-photon detector for qubit readout.
• To leverage ion fluorescence for self-calibration of the photon detector.

Main Methods:

• Utilized a single ^{9}Be^{+} ion in a surface-electrode radiofrequency ion trap.
• Employed a superconducting nanowire single-photon detector fabricated directly into the ion trap structure.
• Counted state-dependent ion fluorescence photons for qubit state determination.

Main Results:

• Achieved an average readout fidelity of 0.9991(1).
• Demonstrated a mean readout duration of 46 microseconds.
• Identified readout laser polarization impurity and off-resonant optical pumping as fidelity limitations.
• Used ion fluorescence to determine detector quantum efficiency and its angular/polarization dependence.

Conclusions:

• Trap-integrated photon detectors enable high-fidelity trapped ion qubit readout.
• The integrated system allows for self-calibration of detector performance.
• This approach advances the development of scalable quantum computing architectures.