One of the main problems in realizing quantum computers is that the states of qubits, which represent the status of computation, change into unintended ones in a short time. This prevents us from implementing quantum algorithms correctly. Constant-step quantum circuits for the OR function are known to be quite useful for inventing techniques that address the problem. However, for over ten years, it has not been known whether such circuits can be constructed or not. In this work, we succeeded in constructing constant-step quantum circuits for various functions, including the OR function. In the future, these circuits will contribute to realizing quantum computers and thus to performing high-speed computation that cannot be done by today’s computers.
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