Experimental quantum computational chemistry with optimised unitary coupled cluster ansatz

Simulation of quantum chemistry is one of the most promising applications of quantum computing. While recent experimental works have demonstrated the potential of solving electronic structures with variational quantum eigensolver (VQE), the implementations are either restricted to nonscalable (hardware efficient) or classically simulable (Hartree-Fock) ansatz, or limited to a few qubits with large errors for the more accurate unitary coupled cluster (UCC) ansatz. Here, integrating experimental and theoretical advancements of improved operations and dedicated algorithm optimisations, we demonstrate an implementation of VQE with UCC for H_2, LiH, F_2 from 4 to 12 qubits. Combining error mitigation, we produce high-precision results of the ground-state energy with error suppression by around two orders of magnitude. For the first time, we achieve chemical accuracy for H_2 at all bond distances and LiH at small bond distances in the experiment. Our work demonstrates a feasible path towards a scalable solution to electronic structure calculation, validating the key technological features and identifying future challenges for this goal.Comment: 8 pages, 4 figures in the main text, and 29 pages supplementary materials with 16 figure

Comment on ‘Targeted Ciphers for Format‐Preserving Encryption’ from Selected Areas in Cryptography 2018

Abstract Format‐preserving encryption (FPE) allows encrypting plaintexts while preserving a specific format. In Selected Areas in Cryptography 2018, two targeted ciphers were proposed as new FPE schemes. The second scheme was designed with an algorithm called Mix–Swap–Unmix that is shown to be equivalent to a particular matching exchange process under a specific setting. In this comment paper, we prove that the matching exchange process is invalid. As a result, this equivalence does not exist

An analytical model of the growth of invisible bubbles on solid surfaces in a supersaturated solution

Heterogeneous nucleation of gas bubbles is central to many engineering fields, from boiling and heat transfer to cavitation and particle separation. In this paper, models accounting for the origin and growth of gas bubbles on solid surfaces in a supersaturated solution are proposed by applying the diffusion theory and the molecular-kinetic model. Both are validated by the available experimental results during the specific period. The theory provides an explanation for the bubbles’ growth from the pre-existing invisible nanobubbles on the submerged surface. The non-linear evolution of the bubble is attributed to the progression from the pinning stage to the floating stage, transition stage and expansion stage. In the pinning stage, when the base radius of the optically invisible surface bubbles is smaller than the critical value they are speculated to be stable with the constant base radius because of the equilibrium between the driving force of diffusion and the Laplace pressure. Otherwise, the contact line of the surface bubble will start to move, is no longer pinned, and continues to grow with a constant bubble radius, which is called the floating stage. This is followed by the transition stage in which both the bubble radius and contact angle change with time. The final expansion stage is characterised by the bubble growth with the constant contact angle. Unlike the classical Epstein-Plesset model for bubble growth in the bulk, the diffusion theory can satisfactorily predict the growth of surface bubbles while the molecular-kinetic model can only fit the floating and expansion stages

Enhanced Thermoelectric Performance of c-Axis-Oriented Epitaxial Ba-Doped BiCuSeO Thin Films

Abstract We reported the epitaxial growth of c-axis-oriented Bi1−x Ba x CuSeO (0 ≤ x ≤ 10%) thin films and investigated the effect of Ba doping on the structure, valence state of elements, and thermoelectric properties of the films. X-ray photoelectron spectroscopy analysis reveal that Bi3+ is partially reduced to the lower valence state after Ba doping, while Cu and Se ions still exist as + 1 and − 2 valence state, respectively. As the Ba doping content increases, both resistivity and Seebeck coefficient decrease because of the increased hole carrier concentration. A large power factor, as high as 1.24 mWm−1 K−2 at 673 K, has been achieved in the 7.5% Ba-doped BiCuSeO thin film, which is 1.5 times higher than those reported for the corresponding bulk samples. Considering that the nanoscale-thick Ba-doped films should have a very low thermal conductivity, high ZT can be expected in the films

High-Linear Frequency-Swept Lasers with Data-Driven Control

The frequency-swept laser (FSL) is applied widely in various sensing systems in the scientific and industrial fields, especially in the light detection and ranging (Lidar) area. However, the inherent nonlinearity limits its performance in application systems, especially in the broadband frequency-swept condition. In this work, from the perspective of data-driven control, we adopt the reinforcement learning-based broadband frequency-swept linearization method (RL-FSL) to optimize the control policy and generate the modulation signals. The nonlinearity measurement system and the system simulator are established. Since the powerful learning ability of the reinforcement learning algorithm, the linearization policy is optimized off-line and the generated modulation signals reduce the nonlinearity almost 20 times, compared to the case without control. In the long-term operation, the regular updated modulation signals perform better than the traditional iteration results, demonstrating the efficiency of the proposed data-driven control method in application systems. Therefore, the RL-FSL method has the potential to be the candidate of optical system control

Characterization of coal pyrolysis in indirectly heated fixed bed based on field effects

This study is devoted to characterizing the coal pyrolysis performance based on field effects in five fixed bed reactors with different radiuses. The results showed that the increased reactor radius raised the coal bed thickness, thereby modifying the temperatures and extending the reaction time to reach 500 degrees C. At a furnace temperature of 900 degrees C, the increased coal bed thickness from 20 mm to 100 mm decreased the tar yield from 7.24 wt% to 5.62 wt%, while it raised the light tar content from 76.4 wt% to 83.0 wt% in the reactor with internals (reactor B). In contrast, in the reactor without internals (reactor A), the tar yield varied marginally and remained at 4.73 wt% but the light tar content increased from 69.5 wt% to 74.7 wt%. The increased coal bed thickness resulted in an increase in the tar quality but a decrease in the gas HHV (higher heating value) for both reactors. However, with the increase of coal bed thickness, reactor B always provides a higher yield and quality of tar and gas but lower pyrolysis water yield than reactor A, indicating that the internals suppressed the secondary reaction of pyrolysis products and the increase in coal bed thickness did not weaken this advantage of internals. The char HHV located in the center of the reactor with internals was higher than that of the reactor without internals; this was postulated that the pyrolysis products escaped from the central low-temperature coal bed, which enhanced carbon deposition. As expected, EDS results proved the postulation and showed that the char in the center of the reactor B had more carbon species. In addition, the color changes of quartz sand in the before and after tests first verified the flow field of pyrolysis products in phenomenology. (C) 2017 Elsevier Ltd. All rights reserved.</p

Corrigendum: ‘An analytical model of the growth of invisible bubbles on solid surfaces in a supersaturated solution’ (Chemical Engineering Science (2020) 215, (S0009250919304361), (10.1016/j.ces.2019.05.004))

The original paper (Yang et al., 2020) contains significant portions of text from the paper published in APCChE 2015 Congress incorporating Chemeca 2015, 27 Sept–01 Oct 2015, Melbourne, Victoria (Yang and Nguyen, 2015). The original text from the paper, Yang and Nguyen (2015) was used without attribution. Yang et al. (2020) extends on the original work (Yang and Nguyen, 2015), which was presented at the APCChE 2015 Congress and published in the conference proceedings. Also, one author of Yang and Nguyen (2015), Anh Nguyen, was not invited to be an author of this paper (Yang et al., 2020). Due to his contribution to the original work (Yang and Nguyen, 2015), Anh Nguyen has been added as an author of this paper and this is corrected with this corrigendum as shown above. The authors would like to apologise for any inconvenience caused

Cu-based high-entropy two-dimensional oxide as stable and active photothermal catalyst

Abstract Cu-based nanocatalysts are the cornerstone of various industrial catalytic processes. Synergistically strengthening the catalytic stability and activity of Cu-based nanocatalysts is an ongoing challenge. Herein, the high-entropy principle is applied to modify the structure of Cu-based nanocatalysts, and a PVP templated method is invented for generally synthesizing six-eleven dissimilar elements as high-entropy two-dimensional (2D) materials. Taking 2D Cu2Zn1Al0.5Ce5Zr0.5Ox as an example, the high-entropy structure not only enhances the sintering resistance from 400 °C to 800 °C but also improves its CO2 hydrogenation activity to a pure CO production rate of 417.2 mmol g−1 h−1 at 500 °C, 4 times higher than that of reported advanced catalysts. When 2D Cu2Zn1Al0.5Ce5Zr0.5Ox are applied to the photothermal CO2 hydrogenation, it exhibits a record photochemical energy conversion efficiency of 36.2%, with a CO generation rate of 248.5 mmol g−1 h−1 and 571 L of CO yield under ambient sunlight irradiation. The high-entropy 2D materials provide a new route to simultaneously achieve catalytic stability and activity, greatly expanding the application boundaries of photothermal catalysis