After passing the entangled light through a two meter long multimode fiber, Natalia Herrera Valencia and her colleagues successfully restored the entangled light to its original state. Led by mayul Malik, the team at the University of heriwat in Edinburgh solved the problem by using entanglement itself. Also involved in the study was a researcher from the University of Glasgow. A recent paper published in nature physics describes the study in detail. < / P > < p > light passing through disordered (or “complex”) media, such as atmospheric fog or multimode fiber, is scattered in known ways. As a result, the information carried by light can be preserved, but it will be distorted. Therefore, additional steps are required to obtain this information. This becomes tricky when entangled light is transmitted, because the medium can disturb the quantum correlation. In order to retrieve the original entangled state, we must first “descramble”. < / P > < p > to understand complex media, physicists use the transfer matrix (i.e., a two-dimensional complex array) to predict the results of any substance passing through the medium. Transmission matrix theory, coupled with some key developments in technology, has only recently allowed classical light to travel through complex media. In this research, the Edinburgh team extended the concept of transfer matrix to the field of quantum optics. < / P > < p > an attribute called “channel state duality” allows researchers to extract the complete transfer matrix of a medium using only one quantum entangled state (a pair of photons with correlated attributes) as a probe. This is different from the classic way of building a matrix. In the classical way, multiple optical probes must be passed through the medium to obtain a complete matrix. < / P > < p > when they know how the medium scrambles information, Herrera Valencia and her colleagues can use the same matrix to eliminate the effect of the medium. Here again, entanglement plays a clever trick: unlike the light passing through the fiber, researchers can scramble its “entangled twins” so that they can get the same result without passing through the medium. They use a device called spatial light modulator (SLM) to scramble light. The device can affect the light field distribution. Compared with two-dimensional qubits, high-dimensional entangled states have greater potential because they can carry more information and are more robust to noise. But these states are also more vulnerable to environmental changes. This study solves a major problem in quantum optics by describing the six dimensional entangled state reservation in space. “Quantum bit entanglement already has the technology to handle channel independent degrees of freedom (such as polarization). However, when it comes to high-dimensional entangled states, there are many problems with spatial pattern coding, “Malik explained. Something as simple as wavefront distortion can also disrupt information. In order to create and measure high-dimensional entangled states, a concept often used by physicists is called spatial degree of freedom. In this study, the team is based on spatial “pixels.”. They divide a continuous location space into discrete regions or pixels. In this way, if a photon is detected in the first pixel of one structure, the entangled twins of the photon should also be detected in the first pixel of another structure. The number of pixels determines the maximum entanglement dimension that may occur in the system. Pixel base points perform very well in terms of quality, speed and dimension. More importantly, spatial light modulator can achieve accurate and lossless control. < / P > < p > in addition to increasing the dimension of entangled states and solving the dispersion problems in long fibers, the research team is also exploring how to apply the idea of complex channel equivalent to quantum states to simplify the measurement of quantum states with large amounts of information. < / P > < p > the team also mentioned in their paper that the technology can even be used to transmit high-dimensional entanglement in dynamic media such as biological tissues. Entangled light can also be transmitted through two independent channels. Controlling either channel can affect the whole state, of course, the other channel. “This function may play a role in quantum network scenarios or in noninvasive biological imaging,” the researchers wrote. Because in these cases, it may not be realistic to reach every part of a complex system. ” (Henglin) < A= https://ibmwl.com/category/global-tech/ target=_ blank>Global Tech