Part of the challenge for quantum many-body problems comes from the difficulty of representing large-scale quantum states, which in general requires an exponentially large number of parameters. ...Neural networks provide a powerful tool to represent quantum many-body states. An important open question is what characterizes the representational power of deep and shallow neural networks, which is of fundamental interest due to the popularity of deep learning methods. Here, we give a proof that, assuming a widely believed computational complexity conjecture, a deep neural network can efficiently represent most physical states, including the ground states of many-body Hamiltonians and states generated by quantum dynamics, while a shallow network representation with a restricted Boltzmann machine cannot efficiently represent some of those states.One of the challenges in studies of quantum many-body physics is finding an efficient way to record the large system wavefunctions. Here the authors present an analysis of the capabilities of recently-proposed neural network representations for storing physically accessible quantum states.
By using a tetraphenylethene (TPE)-based ligand, tetrakis4-(4-carboxyphenyl)phenylethene (H4TCPPE), a porous metal-organic framework Zn2(TCPPE) (1) is synthesized, which exhibits strong fluorescence ...and is capable of gas adsorption and sensing volatile organic compounds.
A novel pillared-layered entangled luminescent metal-organic framework Zn
(bpdc)
(BPyTPE) (1) (BPyTPE = (E)-1,2-diphenyl-1,2-bis(4-(pyridin-4-yl)phenyl)ethene) has been designed and constructed. The ...solvent-free 1 exhibits strong blue-green emission with an excellent fluorescence quantum yield of 99% and provides a facile and reversible method to sensitively and quantitatively detect trace pesticide of 2,6-dichloro-4-nitroaniline.
Hybrid quantum-classical variational algorithms are one of the most propitious implementations of quantum computing on near-term devices, offering classical machine-learning support to quantum scale ...solution spaces. However, numerous studies have demonstrated that the rate at which this space grows in qubit number could preclude learning in deep quantum circuits, a phenomenon known as barren plateaus. In this work, we implicate random entanglement, i.e., entanglement that is formed due to state evolution with random unitaries, as a source of barren plateaus and characterize them in terms of many-body entanglement dynamics, detailing their formation as a function of system size, circuit depth, and circuit connectivity. Using this comprehension of entanglement, we propose and demonstrate a number of barren plateau ameliorating techniques, including initial partitioning of cost function and non-cost function registers, meta-learning of low-entanglement circuit initializations, selective inter-register interaction, entanglement regularization, the addition of Langevin noise, and rotation into preferred cost function eigenbases. We find that entanglement limiting, both automatic and engineered, is a hallmark of high-accuracy training and emphasize that, because learning is an iterative organization process whereas barren plateaus are a consequence of randomization, they are not necessarily unavoidable or inescapable. Our work forms both a theoretical characterization and a practical toolbox; first defining barren plateaus in terms of random entanglement and then employing this expertise to strategically combat them.
In this work, we synthesized a dicarboxyl-substituted tetraphenylethene (TPE) ligand, 4,4′-(1,2-diphenylethene-1,2-diyl)dibenzoic acid (H 2 BCTPE), with a prominent aggregation-induced emission (AIE) ...feature. A two-fold interpenetrated luminescent metal–organic framework (LMOF) Zn 4 O(BCTPE) 3 ( 1 ) with Zn 4 O(CO 2 ) 6 nodes is prepared using the trans -isomer of H 2 BCTPE as a ligand, which shows a typical behavior of microporous materials and a high fluorescence quantum yield of 64.5%. The solvent free 1 is thermally stable, water stable and highly emissive. The suspension of solvent-free 1 in water exhibits high quenching efficiencies and low detection limits towards nitro-containing explosives ( e.g. nitrobenzene, 4-nitrophenol, 2,4,6-trinitrophenol), and nitro-containing antibiotics ( e.g. metronidazole and nitrofurazone). The solvent-free 1 can be a promising alternative to efficiently detect nitro-containing explosives and antibiotics under aqueous conditions.
One of the challenges in water remediation is adsorbent designing, aiming at low cost and ultrafast contaminant adsorption. Herein, we developed a simple and scalable one-pot synthesis method to ...achieve a cost-effective anionic hypercrosslinked polymer ( AHCP-1 ) through the Friedel–Crafts reaction with sodium tetraphenylboron as the monomer. To the best of our knowledge, this is the first anionic hypercrosslinked polymer synthesized using the Friedel–Crafts reaction. Notably, AHCP-1 possessed a high specific surface area of 939 m 2 g −1 with a micro-/mesoporous structure. Owing to the high surface area, the abundant phenyl groups and the built-in ionic charges, AHCP-1 displayed ultrafast adsorption towards dyes and phenolic derivatives, and a high adsorption capacity of 229.89 mg g −1 for RhB and 540.5 mg g −1 for BPA. It is also found that the adsorption behavior is dependent on the pollutant concentration, the pH value, and the structure and charge states of the pollutant molecules.
A novel secondary-side phase-shift-controlled (SS-PSC) LLC resonant converter is proposed for applications requiring hold-up time operation, such as distributed power systems and server power ...supplies. High efficiency at the normal input voltage is achieved because the proposed SS-PSC LLC converter always operates at the series-resonant frequency of the resonant tank. The magnetizing inductor of the proposed converter does not need to be reduced to provide desired voltage boost ratio for the hold-up time operation, which results in reduced conduction losses and improved efficiency. Sufficient voltage boost ratio for the hold-up time operation is provided by using SS-PSC strategy. In comparison with the conventional variable-frequency-controlled (VFC) LLC resonant converter, the main advantages are that the circulating current caused by the magnetizing inductor is effectively suppressed and the efficiency of normal operation is significantly improved. The operation principles, output characteristics, and design considerations of the proposed converter are presented in detail. Experimental results are given to verify the effectiveness and the advantages of the proposed solutions.
The biological luminescent metal-organic framework (bio-LMOF), (Me
2
NH
2
)
2
Zn
6
O(Ade)
4
(TCPPE)
2
(
1
) {H
4
TCPPE = tetrakis4-(4-carboxyphenyl)phenylethene, Ade = adenine} was successfully ...designed and synthesized under hydrothermal conditions, with two channels of different sizes. The absolute fluorescence quantum yields of complex
1
and activated
1
are up to 77.6% and 85.9%, respectively. Activated
1
exhibits outstanding water stability and excellent selective luminescence sensing for amino acids and monosaccharides. The fluorescence quenching efficiencies of activated
1
towards
l
-Nph and
d
-Nga are 86.35% and 91.60%, respectively. Besides, activated
1
also displays highly quenching responses to
l
-Nph and
d
-Nga at fairly low concentrations, and the limits of detection for
l
-Nph and
d
-Nga are estimated to be 0.149 ppm and 1.612 ppm, respectively. Meanwhile, in multiple cycling experiments, activated
1
still has excellent cycling stability. These phenomena indicate that activated
1
can be utilized as a fast responsive biological luminescent sensor, which is a rare example for bio-LMOFs.
A tetraphenylethene-based biological luminescent metal-organic framework with high fluorescence quantum yield is developed for selective and sensitive detection of amino acids and monosaccharides in aqueous medium.
We present the enantioselective synthesis of P-stereogenic phosphinamides through Pd-catalyzed desymmetric ortho C–H arylation of diarylphosphinamides with boronic esters. The method represents the ...first example of the synthesis of P-stereogenic phosphorus compounds via the desymmetric C–H functionalization strategy. The reaction proceeded efficiently with a wide array of reaction partners to afford the P-stereogenic phosphinamides in up to 74% yield and 98% ee. The efficiency was further demonstrated by gram scale syntheses. Moreover, the flexible conversion of the P-stereogenic phosphinamides into various types of P-stereogenic phosphorus derivatives was also elaborated. Thus, the protocol provides a novel tool for the efficient and versatile synthesis of P-stereogenic compounds.
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