Evaluation of innovative sprayed-concrete-lined tunnelling

The front-shunt tunnel was the first tunnel of the Terminal 5 project at Heathrow to be constructed, and was the first section of sprayed-concrete-lined (SCL) tunnel to be constructed using the method known as LaserShell. This innovation represented a significant deviation from the methods previously used in SCL construction. Therefore it was subjected to a careful examination before and during construction using sophisticated 3D numerical modelling and monitoring during construction. The paper presents typical results from surface settlement levelling, inclinometers and extensometers, pressure cells and tunnel lining displacement measurements, and comments on the performance of the methods and instruments used. The paper then presents the methodology and typical results of the numerical modelling, and shows that the predictions of displacements and stresses compared well with the field measurements. In terms of the control of ground deformations and structural safety the tunnel performed well

Optimal nonlocal multipartite entanglement concentration based on projection measurements

We propose an optimal nonlocal entanglement concentration protocol (ECP) for multi-photon systems in a partially entangled pure state, resorting to the projection measurement on an additional photon. One party in quantum communication first performs a parity-check measurement on her photon in an N-photon system and an additional photon, and then she projects the additional photon into an orthogonal Hilbert space for dividing the original $N$-photon systems into two groups. In the first group, the N parties will obtain a subset of $N$-photon systems in a maximally entangled state. In the second group, they will obtain some less-entangled N-photon systems which are the resource for the entanglement concentration in the next round. By iterating the entanglement concentration process several times, the present ECP has the maximal success probability which is just equivalent to the entanglement of the partially entangled state. That is, this ECP is an optimal one.Comment: 5 pages, 4 figure

Quantum mechanical photon-count formula derived by entangled state representation

By introducing the thermo entangled state representation, we derived four new photocount distribution formulas for a given density operator of light field. It is shown that these new formulas, which is convenient to calculate the photocount, can be expressed as such integrations over Laguree-Gaussian function with characteristic function, Wigner function, Q-function, and P-function, respectively.Comment: 5 pages, no figur

Efficient multipartite entanglement purification with the entanglement link from a subspace

We present an efficient multipartite entanglement purification protocol (MEPP) for N-photon systems in a Greenberger-Horne-Zeilinger state with parity-check detectors. It contains two parts. One is the conventional MEPP with which the parties can obtain a high-fidelity N-photon ensemble directly, similar to the MEPP with controlled-not gates. The other is our recycling MEPP in which the entanglement link is used to produce some $N$-photon entangled systems from entangled N'-photon subsystems (2 \leq N'<N) coming from the instances which are just discarded in all existing conventional MEPPs. The entangled N'-photon subsystems are obtained efficiently by measuring the photons with potential bit-flip errors. With these two parts, the present MEPP has a higher efficiency than all other conventional MEPPs.Comment: 17 pages, 9 figures, 2 tables. We correct the error in the address of the author in the published version (Phys. Rev. A 84, 052312 (2011)

Modes of zonal mean temperature variability 20–100 km from the TIMED/SABER observations

In this study we investigate the spatial variabilities of the zonal mean temperature (20–100 km) from the TIMED (Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics)/SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) satellite using the empirical orthogonal functions (EOFs). After removing the climatological annual mean, the first three EOFs are able to explain 87.0% of temperature variabilities. The primary EOF represents 74.1% of total anomalies and is dominated by the north–south contrast. Patterns in the second and third EOFs are related to the semiannual oscillations (SAO) and mesospheric temperature inversions (MTI), respectively. The quasi-biennial oscillation (QBO) component is also decomposed into the seventh EOF with contributions of 1.2%. Last, we use the first three modes and annual mean temperature to reconstruct the data. The result shows small differences are in low latitude, which increase with latitude in the middle stratosphere and upper mesosphere