Joint measurement of multiple noncommuting parameters

Although quantum metrology allows us to make precision measurements beyond the standard quantum limit, it mostly works on the measurement of only one observable due to the Heisenberg uncertainty relation on the measurement precision of noncommuting observables for one system. In this paper, we study the schemes of joint measurement of multiple observables which do not commute with each other using the quantum entanglement between two systems. We focus on analyzing the performance of a SU(1,1) nonlinear interferometer on fulfilling the task of joint measurement. The results show that the information encoded in multiple noncommuting observables on an optical field can be simultaneously measured with a signal-to-noise ratio higher than the standard quantum limit, and the ultimate limit of each observable is still the Heisenberg limit. Moreover, we find a resource conservation rule for the joint measurement

Loss-tolerant quantum dense metrology with SU(1,1) interferometer

Heisenberg uncertainty relation in quantum mechanics sets the limit on the measurement precision of non-commuting observables in one system, which prevents us from measuring them accurately at the same time. However, quantum entanglement between two systems allows us to infer through Einstein-Podolsky-Rosen correlations two conjugate observables with precision better than what is allowed by Heisenberg uncertainty relation. With the help of the newly developed SU(1,) interferometer, we implement a scheme to jointly measure information encoded in multiple non-commuting observables of an optical field with a signal-to-noise ratio improvement of about 20% over the classical limit on all measured quantities simultaneously. This scheme can be generalized to the joint measurement of information in arbitrary number of non-commuting observables

Phase Diagram of Superconductivity on the Anisotropic Triangular Lattice Hubbard Model

We study the electronic states of the anisotropic triangular lattice Hubbard model at half filling, which is a simple effective model for the organic superconducting $\kappa$-BEDT-TTF compounds. We treat the effect of the Coulomb interaction by the fluctuation exchange (FLEX) method, and obtain the phase diagram of this model for various sets of parameters. It is shown that the d-wave superconductivity is realized in the wide region of the phase diagram, next to the antiferromagnetic states. The obtained phase diagram explains the characters of the experimental results very well.Comment: 4 pages, 6 figs, submitted for publicatio

Hemodynamic effects of nitroglycerin in an experimental model of acute aortic regurgitation

AbstractAfterload reduction is an accepted therapeutic modality for the treatment of congestive heart failure caused by chronic aortic regurgitation. However, the role of vasodilator therapy in acute aortic incompetence has not been established. To investigate this, left ventricular volume overload was produced in 18 dogs by constructing a valved conduit from the descending thoracic aorta to the left ventricular apex. The time course of aortic, pulmonary and conduit flows was analyzed in eight control studies and established stability of the experimental model.In the remaining 10 dogs, intravenous nitroglycerin, titrated to reduce mean aortic blood pressure by 40%, and placebo (ethanol) were each infused for 20 min periods. Compared with placebo, nitroglycerin significantly reduced aortic flow (3,945 ± 324 to 3,397 ± 362 ml/min, p < 0.01), regurgitant flow (1,304 ± 131 to 764 ± 90 ml/min, p < 0.001), septal-lateral end-diastolic diameter (47.5 ± 1.8 to 46.5 ± 1.8 mm, p < 0.001), left ventricular end-diastolic pressure (6.9 ± 0.8 to 6.0 ± 0.6 mm Hg, p < 0.05), left ventricular stroke work (19.0 ± 2.6 to 10.8 ± 1.7 g-m/beat, p < 0.001) and systemic vascular resistance (2,253 ± 173 to 1,433 ± 117 dyne-s/cm5, p < 0.001). In contrast, pulmonary flow, left anterior descending coronary flow and subendocardial pH did not change during infusion of either nitroglycerin or placebo.These data indicate that by decreasing preload and afterload, and by preserving coronary flow and tissue pH, nitroglycerin effectively reduced ventricular and regurgitant volumes in the setting of acute volume overload. This study supports the clinical use of nitroglycerin in severe acute aortic incompetence

Effects of Multiple Sintering Parameters on the Thermal Performance of Bi-porous Nickel Wicks in Loop Heat Pipes

This document is the Accepted Manuscript version of the following article: Y. Qu, K. Zhou, K. F. Zhang and Y. Tian, ‘Effects of multiple sintering parameters on the thermal performance of bi-porous nickel wicks in Loop Heat Pipes’, International Journal of Heat and Mass Transfer, Vol. 99: 638-646, August 2016, doi: http://dx.doi.org/10.1016/j.ijheatmasstransfer.2016.04.005. This manuscript version is made available under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License CC BY NC-ND 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited, and is not altered, transformed, or built upon in any way.The thermal performance of a water-saturated Loop Heat Pipe (LHP) with bi-porous nickel wicks has been examined theoretically and experimentally, based on five key influencing factors including the content of foaming agent, compacting pressure, incubation time at suitable temperature, sintering temperature and particle size of foaming agent. Comparison was made among a total number of 20 tests with each influencing factor allocated by four different values, where porosity, permeability, capillary suction head and effective thermal conductivity (ETC) were examined. ETC is an important parameter of thermal performance, and its experimental values were compared with eleven theoretical models. The results showed that ETC was mostly affected by the content of foaming agent: 1.9-2.2 times compared to the effect of compacting pressure and incubation time, with the effect of sintering temperature and particle size of foaming agent ata underestimated the true ETC values. In the porosity range of 0.5-0.7, an average of the Chernysheva & Maydanik model and the Chaudhary & Bhandari model was found to be the best fit to the experimental data, providing an accurate method to predict ETC values of water-saturated LHP with bi-porous nickel wicks.Peer reviewedFinal Accepted Versio

Resource-efficient high-dimensional subspace teleportation with a quantum autoencoder.

Quantum autoencoders serve as efficient means for quantum data compression. Here, we propose and demonstrate their use to reduce resource costs for quantum teleportation of subspaces in high-dimensional systems. We use a quantum autoencoder in a compress-teleport-decompress manner and report the first demonstration with qutrits using an integrated photonic platform for future scalability. The key strategy is to compress the dimensionality of input states by erasing redundant information and recover the initial states after chip-to-chip teleportation. Unsupervised machine learning is applied to train the on-chip autoencoder, enabling the compression and teleportation of any state from a high-dimensional subspace. Unknown states are decompressed at a high fidelity (~0.971), obtaining a total teleportation fidelity of ~0.894. Subspace encodings hold great potential as they support enhanced noise robustness and increased coherence. Laying the groundwork for machine learning techniques in quantum systems, our scheme opens previously unidentified paths toward high-dimensional quantum computing and networking

Accessible precisions for estimating two conjugate parameters using Gaussian probes

We analyze the precision limits for a simultaneous estimation of a pair of conjugate parameters in a displacement channel using Gaussian probes. Having a set of squeezed states as an initial resource, we compute the Holevo Cramér-Rao bound to investigate the best achievable estimation precisions if only passive linear operations are allowed to be performed on the resource prior to probing the channel. The analysis reveals the optimal measurement scheme and allows us to quantify the best precision for one parameter when the precision of the second conjugate parameter is fixed. To estimate the conjugate parameter pair with equal precision, our analysis shows that the optimal probe is obtained by combining two squeezed states with orthogonal squeezing quadratures on a 50:50 beam splitter. If different importance is attached to each parameter, then the optimal mixing ratio is no longer 50:50. Instead, it follows a simple function of the available squeezing and the relative importance between the two parameters