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Spatial transcriptomics data is invaluable for understanding the spatial organization of gene expression in tissues. There have been consistent efforts in studying how to effectively utilize the associated spatial information for refining gene expression modeling. We introduce a class of distance-preserving generative models for spatial transcriptomics, which utilizes the provided spatial information to regularize the learned representation space of gene expressions to have a similar pair-wise distance structure. This helps the latent space to capture meaningful encodings of genes in spatial proximity. We carry out theoretical analysis over a tractable loss function for this purpose and formalize the overall learning objective as a regularized evidence lower bound. Our framework grants compatibility with any variational-inference-based generative models for gene expression modeling. Empirically, we validate our proposed method on the mouse brain tissues Visium dataset and observe improved performance with variational autoencoders and scVI used as backbone models.

Estimating the counterfactual outcome of treatment is essential for decision-making in public health and clinical science, among others. Often, treatments are administered in a sequential, time-varying manner, leading to an exponentially increased number of possible counterfactual outcomes. Furthermore, in modern applications, the outcomes are high-dimensional and conventional average treatment effect estimation fails to capture disparities in individuals. To tackle these challenges, we propose a novel conditional generative framework capable of producing counterfactual samples under time-varying treatment, without the need for explicit density estimation. Our method carefully addresses the distribution mismatch between the observed and counterfactual distributions via a loss function based on inverse probability re-weighting, and supports integration with state-of-the-art conditional generative models such as the guided diffusion and conditional variational autoencoder. We present a thorough evaluation of our method using both synthetic and real-world data. Our results demonstrate that our method is capable of generating high-quality counterfactual samples and outperforms the state-of-the-art baselines., Comment: Published at KDD'24

Although individual carbon nanotubes (CNTs) are superior as constituents to polymer chains, the mechanical and thermal properties of CNT fibers (CNTFs) remain inferior to commercial synthetic fibers due to the lack of synthesis methods to embed CNTs effectively in superstructures. The application of conventional techniques for mechanical enhancement resulted in a mild improvement of target properties while achieving parity at best on others. In this work, a Double-Drawing technique is developed to deform continuously grown CNTFs and rearrange the constituent CNTs in both mesoscale and nanoscale morphology. Consequently, the mechanical and thermal properties of the resulting CNTFs can be jointly improved, and simultaneously reach their highest performances with specific strength (tenacity) $\rm\sim3.30\,N\,tex^{-1}$, work of rupture $\rm\sim70\,J\,g^{-1}$, and thermal conductivity $\rm\sim354\,W\,m^{-1}\,K^{-1}$, despite starting from commercial low-crystallinity materials ($I{\rm_G}:I{\rm_D}\sim5$). The processed CNTFs are more versatile than comparable carbon fiber, Zylon, Dyneema, and Kevlar. Furthermore, based on evidence of load transfer efficiency on individual CNTs measured with In-Situ Stretching Raman, we find the main contributors to property enhancements are (1) the increased proportion of load-bearing CNT bundles and (2) the extension of effective length of tubes attached on these bundles., Comment: 27 pages, 8 figures, research article (main text+supporting information)

Quantum channels breaking entanglement, incompatibility, or nonlocality are defined as such because they are not useful for entanglement-based, one-sided device-independent, or device-independent quantum information processing, respectively. Here, we show that such breaking channels are related to complementary tests of macrorealism i.e., temporal separability, channel unsteerability, temporal unsteerability, and the temporal Bell inequality. To demonstrate this we first define a steerability-breaking channel, which is conceptually similar to entanglement and nonlocality-breaking channels and prove that it is identical to an incompatibility-breaking channel. A hierarchy of quantum non-breaking channels is derived, akin to the existing hierarchy relations for temporal and spatial quantum correlations. We then introduce the concept of channels that break temporal correlations, explain how they are related to the standard breaking channels, and prove the following results: (1) A robustness-based measure for non-entanglement-breaking channels can be probed by temporal nonseparability. (2) A non-steerability-breaking channel can be quantified by channel steering. (3) Temporal steerability and non-macrorealism can be used for, respectively, distinguishing unital steerability-breaking channels and nonlocality-breaking channels for a maximally entangled state. Finally, a two-dimensional depolarizing channel is experimentally implemented as a proof-of-principle example to demonstrate the hierarchy relation of non-breaking channels using temporal quantum correlations, Comment: Comments welcome

Given a non-empty closed convex subset $\mathsf{F}$ of density matrices, we formulate conditions that guarantee the existence of an $\mathsf{F}$-morphism (namely, a completely positive trace-preserving linear map that maps $\mathsf{F}$ into itself) between two arbitrarily chosen density matrices. While we allow errors in the transition, the corresponding map is required to be an exact $\mathsf{F}$-morphism. Our findings, though purely geometrical, are formulated in a resource-theoretic language and provide a common framework that comprises various resource theories, including the resource theories of bipartite and multipartite entanglement, coherence, athermality, and asymmetric distinguishability. We show how, when specialized to some situations of physical interest, our general results are able to unify and extend previous analyses. We also study conditions for the existence of maximally resourceful states, defined here as density matrices from which any other one can be obtained by means of a suitable $\mathsf{F}$-morphism. Moreover, we quantitatively characterize the paradigmatic tasks of optimal resource dilution and distillation, as special transitions in which one of the two endpoints is maximally resourceful., Comment: v2: minor changes, accepted in J.Phys.A; v1: 17 pages, 1 figure

Given a Bell inequality, if its maximal quantum violation can be achieved only by a single set of measurements for each party or a single quantum state, up to local unitaries, one refers to such a phenomenon as self-testing. For instance, the maximal quantum violation of the Clauser-Horne-Shimony-Holt inequality certifies that the underlying state contains the two-qubit maximally entangled state and the measurements of one party contains a pair of anti-commuting qubit observables. As a consequence, the other party automatically verifies the set of states remotely steered, namely the "assemblage", is in the eigenstates of a pair of anti-commuting observables. It is natural to ask if the quantum violation of the Bell inequality is not maximally achieved, or if one does not care about self-testing the state or measurements, are we capable of estimating how close the underlying assemblage is to the reference one? In this work, we provide a systematic device-independent estimation by proposing a framework called "robust self-testing of steerable quantum assemblages". In particular, we consider assemblages violating several paradigmatic Bell inequalities and obtain the robust self-testing statement for each scenario. Our result is device-independent (DI), i.e., no assumption is made on the shared state and the measurement devices involved. Our work thus not only paves a way for exploring the connection between the boundary of quantum set of correlations and steerable assemblages, but also provides a useful tool in the areas of DI quantum certification. As two explicit applications, we show 1) that it can be used for an alternative proof of the protocol of DI certification of all entangled two-qubit states proposed by Bowles et al., and 2) that it can be used to verify all non-entanglement-breaking qubit channels with fewer assumptions compared with the work of Rosset et al., Comment: Comments welcome! The MATLAB codes to accompany this work can be found at https://git.io/Jvnmn . v2: A paragraph was added in Discussion Section. v3: Accepted version. Major revision on self-testing complex-valued assemblages