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Register a new userSupramolecular transmission of soliton-encoded bit streams over astronomical distances
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A stream of optical pulses, transmitted over long distances in optical fiber, will be affected by a variety of noise sources, leading to degradation in the signal-to-noise ratio. This noise accumulation sets generic capacity limits of all fiber-based optical signal transmission systems and has long been regarded as unavoidable. We report that by tailoring long-range, non-covalent inter-pulse interactions, optical solitons in a fiber laser loop can robustly couple to each other and self-assemble into supramolecular structures that exhibit long-term stability, elementary diversity and the possibility of information encoding. We demonstrate error-free transmission of such self-assembled solitonic structures over many astronomical units without any active retiming, opening up the possibility of using bit-bit interactions to overcome noise accumulation in optical fiber telecommunications and bit-storage systems.
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We report what we believe is the weakest interaction between solitons ever observed. Our experiment involves temporal optical cavity solitons recirculating in a coherently-driven passive optical fibre ring resonator. We observe two solitons, separated by up to 8,000 times their width, changing their temporal separation by a fraction of an attosecond per round-trip of the 100 m-long resonator, or equivalently 1/10,000 of the wavelength of the soliton carrier wave per characteristic dispersive length. The interactions are so weak that, at the speed of light, they require an effective propagation distance of the order of an astronomical unit to fully develop, i.e. tens of millions of kilometres. The interaction is mediated by transverse acoustic waves generated in the optical fibre by the propagating solitons through electrostriction.
Spatial modes of light can potentially carry a vast amount of information, making them promising candidates for both classical and quantum communication. However, the distribution of such modes over large distances remains difficult. Intermodal coupling complicates their use with common fibers, while free-space transmission is thought to be strongly influenced by atmospheric turbulence. Here we show the transmission of orbital angular momentum modes of light over a distance of 143 kilometers between two Canary Islands, which is 50 times greater than the maximum distance achieved previously. As a demonstration of the transmission quality, we use superpositions of these modes to encode a short message. At the receiver, an artificial neural network is used for distinguishing between the different twisted light superpositions. The algorithm is able to identify different mode superpositions with an accuracy of more than 80% up to the third mode order, and decode the transmitted message with an error rate of 8.33%. Using our data, we estimate that the distribution of orbital angular momentum entanglement over more than 100 kilometers of free space is feasible. Moreover, the quality of our free-space link can be further improved by the use of state-of-the-art adaptive optics systems.
Valley degree of freedom, an excellent information carrier in valleytronics, has been further introduced into advanced microstructure systems for achieving the acoustic valley-Hall topological insulators (VHTIs), which host valley-projected edge states suppressing the undesired sound backscattering under certain perturbations. Therein, the majority of previous literatures focused on single frequency region, and the lack of capability of simultaneous multi-band operation with individual control radically impedes their potential applications. Here, a binary topological-encoded acoustic VHTI is investigated both theoretically and experimentally to manipulate each of the dual-band valley-projected edge states. Through arranging different coding elements derived from the combined valley-Chern numbers, the existence and propagation directions of the frequency selective edge states can be configured in corresponding frequency regions individually. On this basis, three types of proof-of-concept acoustic topological-encoded functional devices are designed, including frequency beam splitter, anti-interference demultiplex topological sensing and composite topological whispering gallery. Our proposal may provide versatile possibilities for achieving the integrated multifunctional systems in multi-channel signal processing and memorizing with high efficiency and high capacity.
We revisit the complexity of online computation in the cell probe model. We consider a class of problems where we are first given a fixed pattern or vector $F$ of $n$ symbols and then one symbol arrives at a time in a stream. After each symbol has arrived we must output some function of $F$ and the $n$-length suffix of the arriving stream. Cell probe bounds of $Omega(deltalg{n}/w)$ have previously been shown for both convolution and Hamming distance in this setting, where $delta$ is the size of a symbol in bits and $winOmega(lg{n})$ is the cell size in bits. However, when $delta$ is a constant, as it is in many natural situations, these previous results no longer give us non-trivial bounds. We introduce a new lop-sided information transfer proof technique which enables us to prove meaningful lower bounds even for constant size input alphabets. We use our new framework to prove an amortised cell probe lower bound of $Omega(lg^2 n/(wcdot lg lg n))$ time per arriving bit for an online version of a well studied problem known as pattern matching with address errors. This is the first non-trivial cell probe lower bound for any online problem on bit streams that still holds when the cell sizes are large. We also show the same bound for online convolution conditioned on a new combinatorial conjecture related to Toeplitz matrices.
We analyze temporal and spectral characteristics of Akhmediev breather and establish amplification and transmission of attenuated multi-soliton in nonlinear optical fiber. Our results show that the attenuated multi-soliton can be converted into Akhmediev breather through a judicious modulation of the spectrum. Subsequently, the maximally compressed pulse train of Akhmediev breather can be used to establish a robust breathing transmission by another spectrum modulation. In addition, the influence of the spectral modulation intensity on the excitation of Akhmediev breather and transmission of maximally compressed pulse train are also discussed.
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