Narrow Linewidth Semiconductor Laser for Ba+ Quantum Applications

Quantum phenomena of superposition paved the way for the quantum computer demonstrations utilizing different approaches of qubit creation and manipulation, such as, based on trapped ions, neutral atoms, nitrogen vacancies, photonic integrated circuits, superconducting loops, etc. The trapped-ion-based platform demonstrated record long coherence times, high-fidelity gates, qubit connectivity and potential for fault-tolerant operation [1]. Number of atomic species have been investigated as basis for qubits and various qubit types along with state-preparation and measurement (SPAM) techniques have been developed. These qubit initialization and readout operations as well as atomic ion preparation stages of photoionization and atom cooling are implemented by single-frequency lasers with narrow emission linewidths at frequencies corresponding to electronic transitions in atomic ion specie. Therefore, several single-frequency lasers with well-defined parameters such as linewidth, output power, polarization, intensity noise are required for trapped-ion-based quantum computer. Considering that currently there are about 11 ion species being employed as qubits, thus more than 100 different laser wavelengths are required across the spectrum. For practical use, scalability of quantum computer is required, i.e., steady increase of qubits number without the loss of quantum system control. Therefore, availability and performance of single-frequency stabilized laser systems with tailorable emission parameters is one of pre-requirements for quantum information processing field development and commercialization success.