In the last decade, a common information hiding technique applied to lossy compressed images embeds secret data by adjusting the indices formed by the vector quantization (VQ) scheme. After extracting embedded data, this method cannot recover the original VQ-compressed codes. This method is called the irreversible information hiding method. On the contrary, the technique which is able to recover the original VQ-compressed codes after extracting of the embedded data is called the reversible information hiding method. There is little research related to reversible information hiding methods for the VQ-compressed images. In this paper, we propose a simple and adaptive reversible information hiding method applied to a VQ-compressed image. In our method, the VQ-compressed image is further compressed using the search-order coding algorithm. It simultaneously embeds the data bits into the indices. Our method embeds any length of data bits into the VQ-compressed image. The experiment results show our method outperforms other methods in embedding capacity and compression ratio.
We investigate photon coalescence in a lossy non-Hermitian system and study a dynamic device modeled by a beam splitter with an extra intrinsic phase term added in the transformation matrix, with which the device is a lossy non-Hermitian linear system. The two-photon interference behavior is altered accordingly since this extra intrinsic phase affects the unitary of transformation and the coalescence of the incoming photons. We calculate the coincidence between two single-photon pulses, considering the interferometric phase between two pulses and the extra intrinsic phase as the tunable parameters. The extra phase turns the famous Hong–Ou–Mandel dip into a bump, with the visibility dependent on both the interferometric phase and the extra phase.
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