One crucial requirement for quantum computation, communication, and metrology is the highly efficient and fast readout of qubit states. For atomic qubits, the frequently used fluorescence method enables a detection efficiency of almost unity, yet, at the cost of long detection times. To reduce the measurement duration one can either increase the numerical aperture of the collection optics or enhance fluorescence via optical cavities. With elaborated fluorescence collection the detection times can be reduced below 10 μs per atom while optical cavities allow detection times below 1 μs. Due to the typically small mode volume and reduced optical access, scalability to a large number of atoms may be challenging for these technologies. Here we show how hyperfine-state-selective photoionization and subsequent detection of the generated photoion-electron pairs enable fast and efficient state analysis.
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