Monogamy relations characterize the distributions of entanglement in multipartite systems. We investigate monogamy relations related to the concurrence C, the entanglement of formation E, negativity Nc and Tsallis-q entanglement Tq. Monogamy relations for the αth power of entanglement have been derived, which are tighter than the existing entanglement monogamy relations for some classes of quantum states. Detailed examples are presented.

Quantum gates in experiment are inherently prone to errors that need to be characterized before they can be corrected. Full characterization via quantum process tomography is impractical and often unnecessary. For most practical purposes, it is enough to estimate more general quantities such as the average fidelity. Here we use a unitary 2-design and twirling protocol for efficiently estimating the average fidelity of Clifford gates, to certify a 7-qubit entangling gate in a nuclear magnetic resonance quantum processor. Compared with more than 10 8 experiments required by full process tomography, we conducted 1656 experiments to satisfy a statistical confidence level of 99%. The average fidelity of this Clifford gate in experiment is 55.1%, and rises to 87.5% if the infidelity due to decoherence is removed. The entire protocol of certifying Clifford gates is efficient and scalable, and can easily be extended to any general quantum information processor with minor modifications. . Introduction. Benchmarking protocols for characterizing the level of coherent control are fundamental in evaluating potential quantum information processing (QIP) devices. They provide an objective comparison of quantum control capabilities between diverse QIP devices, and also indicate the prospects of a given platform with respect to fault-tolerant quantum computation [1]. The traditional approach of using quantum process tomography (QPT) [2,3] is useful for completely characterizing a quantum channel, and has been applied to at most 3-qubit systems in experiment [4][5][6][7][8][9][10][11]. However, QPT requires number of measurements that scale exponentially with number of qubits n (≈ 2 4n ), making it impractical even in relatively small systems. Moreover,for many practical purposes, such as benchmarking, the full description of a particular quantum channel is not necessary and more accessible properties of the gates are sufficient. To benchmark a gate it is enough to estimate the distance between the implemented channel and the ideal gate. Several methods such as randomized benchmarking [12][13][14], twirling [15][16][17], and Monte Carlo estimations [18,19] have been proposed to evaluate a particular quantum channel in an efficient manner, each with its own restrictions and drawbacks. Here, in order to benchmark our coherent controls on a 7-qubit nuclear magnetic resonance (NMR) system, we adopted the twirling protocol [17] to estimate the average fidelity of an important Clifford gate in QIP. The gate of interest generates maximal coherence from single coherence with the aid of lo-

In recent years, mobile payment as an innovative payment method has triggered a payment revolution in China. Understanding and investigating the psychological elements and influence paths that affect the user's willingness to use mobile payment are of great importance. The main purpose of this study is to investigate the effects of a user's risk perception, perceived ease of use, perceived usefulness, and attitude on a user's willingness to use Alipay, by using an extended version of the technology acceptance model (TAM). The model was tested with the use of structural equation modeling (SEM), and the data was collected from 491 users in China. The results show that perceived ease of use and perceived usefulness has a significant effect on users' attitudes and intentions to use Alipay, and the risk perception has a negative effect on perceived ease of use and perceived usefulness. Meanwhile, risk perception also has a direct effect on users' attitudes and intentions to use Alipay. These results suggested that when users perceived that the risks of using Alipay are higher, they will hold a negative attitude using Alipay and less likely to use Alipay. Based on these results, the possible implications have been identified.

The Kerr metric of spherically symmetric gravitational field is analyzed through the coordinate transformation from the rotating frame to fixing frame, and consequently that the inertial force field (with the exception of the centrifugal force field) in the rotating system is one part of its gravitomagnetic field is verified. We investigate the spin-rotation coupling and, by making use of Lewis-Riesenfeld invariant theory, we obtain exact solutions of the Schr\"{o}dinger equation of a spinning particle in a time-dependent rotating reference frame. A potential application of these exact solutions to the investigation of Earth$^{,}$s rotating frequency fluctuation by means of neutron-gravity interferometry experiment is briefly discussed in the present paper.Comment: 6 pages, 0 figures, Late

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As of today, no one can tell when a universal quantum computer with thousands of logical quantum bits (qubits) will be built. At present, most quantum computer prototypes involve less than ten individually controllable qubits, and only exist in laboratories for the sake of either the great costs of devices or professional maintenance requirements. Moreover, scientists believe that quantum computers will never replace our daily, every-minute use of classical computers, but would rather serve as a substantial addition to the classical ones when tackling some particular problems. Due to the above two reasons, cloud-based quantum computing is anticipated to be the most useful and reachable form for public users to experience with the power of quantum. As initial attempts, IBM Q has launched influential cloud services on a superconducting quantum processor in 2016, but no other platforms has followed up yet. Here, we report our new cloud quantum computing service -NMRCloudQ (http://nmrcloudq.com/zh-hans/), where nuclear magnetic resonance, one of the pioneer platforms with mature techniques in experimental quantum computing, plays as the role of implementing computing tasks. Our service provides a comprehensive software environment preconfigured with a list of quantum information processing packages, and aims to be freely accessible to either amateurs that look forward to keeping pace with this quantum era or professionals that are interested in carrying out real quantum computing experiments in person. In our current version, four qubits are already usable with in average 1.26% single-qubit gate error rate and 1.77% two-qubit controlled-NOT gate error rate via randomized benchmaking tests. Improved control precisions as well as a new seven-qubit processor are also in preparation and will be available later.

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