Efficient preparation of lossless quantum images based on Gray code

The initialization of desired quantum states is usually the starting element of quantum algorithms. For quantum image processing, inefficient preparation of quantum images hinders the implement of algorithms on quantum devices. In this study, a ready-to-use quantum circuit simplification method for preparing quantum images is proposed. By encoding the control qubits of the multi-qubit gates as Gray code, an optimized circuit for preparing lossless quantum images is constructed using a technique for simultaneously initializing adjacent pixels. This technique decreases the necessary number of control qubits and the depth of preparation circuits. By validating the proposed algorithm on a medical image dataset, it is demonstrated that a satisfactory depth reduction can be achieved without any quality loss when preparing quantum images.