High-Fidelity Bell-State Preparation with ^{40}Ca^{+} Optical Qubits

Area of Science:

• Quantum Information Science
• Atomic Physics
• Quantum Computing

Background:

• Entanglement generation in trapped ions typically uses Mølmer-Sørensen or light-shift gates.
• A proposed variant separates qubit levels by an optical frequency, potentially improving gate performance.

Purpose of the Study:

• To experimentally demonstrate the proposed frequency-detuned light-shift entangling gate.
• To evaluate the gate's fidelity and error rates in a trapped-ion system.

Main Methods:

• Utilized a pair of ^{40}Ca^{+} ions in a cryogenic surface-electrode ion trap.
• Employed a commercial, high-power, 532 nm Nd:YAG laser for the entangling gate operation.
• Generated a Bell state and directly measured the gate infidelity.

Main Results:

• Successfully generated a Bell state in 35 μs.
• Achieved a directly measured infidelity of 6(3)×10^{-4} without error subtraction.
• The 532 nm laser wavelength suppressed intrinsic photon scattering error to approximately 1×10^{-5}.

Conclusions:

• The frequency-detuned light-shift gate is a viable method for high-fidelity entanglement in trapped ions.
• This approach offers reduced photon scattering, enhancing the potential for scalable quantum computation.
• The demonstrated technique provides a promising avenue for advancing trapped-ion quantum technologies.