The rapid improvement in gate fidelity of coherent operations means that errors in state preparation and measurement (SPAM) may become a major source of errors in fault-tolerant operations in quantum computers. . This is especially acute in superconducting systems where the trade-off between measurement fidelity and qubit lifetime limits overall performance. Fortunately, the inherently classical nature of preparation and measurement allows for a variety of techniques to improve quality using ancillary qubits in combination with classical control and post-selection. will be In practice, however, post-selection greatly complicates the scheduling of processes such as syndrome extraction. Here we present a family of quantum circuits that prepare high-quality |0> states without postselection, instead of nonlinearly permuting the computational base using CNOT and Toffoli gates. A fidelity error below 0.2% for a two-qubit gate yields significant performance improvements, and even better performance when native his Toffoli gates are available.

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