Researchers studied the unique spectral structure of laser noise and introduced a metric that determines when a stabilised laser source has been optimised for quantum control of atomic qubits.
Technical noise present in laser systems can limit their ability to perform high fidelity quantum control of atomic qubits. The ultimate fidelity floor for atomic qubits driven with laser radiation is due to spontaneous emission from excited energy levels. The goal is to suppress the technical noise from the laser source to below the spontaneous emission floor such that it is no longer a limiting factor. It has been shown that the spectral structure of control noise can have a large influence on achievable control fidelities, while prior studies of laser noise contributions have been restricted to noise magnitudes.
They found requirements on stabilisation bandwidths that can be orders of magnitude higher than those required to simply narrow the linewidth of a laser. The introduced metric, the χ-separation line, provides a tool for the study and engineering of laser sources for quantum control of atomic qubits below the spontaneous emission floor.
The paper has been published in npj Quantum.