Quantum block coherence with respect to projective measurements

Quantum coherence serves as a defining characteristic of quantum mechanics,finding extensive applications in quantum computing and quantum communication processing.This study explores quantum block coherence in the context of projective measurements,focusing on the quantification of such coherence.Firstly,we define the correlation function between the two general projective measurements P and Q,and analyze the connection between sets of block incoherent states related to two compatible projective measurements P and Q.Secondly,we discuss the measure of quantum block coherence with respect to projective measurements.Based on a given measure of quantum block coherence,we characterize the existence of maximal block coherent states through projective measurements.This research integrates the compatibility of projective measurements with the framework of quantum block coherence,contributing to the advancement of block coherence measurement theory.

Quantum parameter estimation in a spin-boson dephasing quantum system by periodical projective measurements

In this paper,we explore how to estimate the phase damping parameter γ and the tunneling amplitude parameter ？from a spin-boson dephasing quantum model by periodical projective measurements.The preparation of initial states is accomplished by performing the period measurements in our scheme.The parameter γ can be always estimated when projective measurement bases are chosen as θ = π/2 and φ = 0.Based on the estimated value of γ and the interval information of ？,we can select another measurement bases（θ = π/4 and φ = π/2） to obtain the estimated value of ？.A coherent control is indispensable to estimate ？ if γ is in the interval of ？;whereas the control is not necessary if γ is out of the known interval of ？.We establish the relation between the optimal period time and the parameter γ or ？ in terms of Fisher information.Although the optimal measurement period cannot be selected beforehand,the aforementioned relation can be utilized to adjust the measurement period to approach the optimal one.

Local distinguishability by projective measurement

This paper proves that a set of orthogonal pure states are indistinguishable by restricted local projective measurement and classical communication if the sum of their Schmidt ranks is larger than the dimension of their joint Hilbert space. This result is useful in determining the local distinguishability of quantum states and is stronger in some respects than that of Hayashi et al [Phys. Rev. Lett. 96, 040501]. In addition, it presents a new method to determine the local distinguishability of orthogonal states by projecting measurement operators into their subspaces.

Critical Barriers to Traditional Project Progress Measurement: Perspectives of Ghanaian Construction Professionals

Accurate project progress measurement is critical for effective project management. Besides guarantying smooth work progress, it affords project managers the chance to identify early warning signs for peremptory remedial actions to keep the project on schedule and to budget. However, pertinent barriers can suppress the realization of the benefits of an accurate assessment of construction progress. This study aims to identify, examine and prioritize the critical barriers militating against accurate project progress measurement in the Ghanaian construction industry. Sixteen barriers identified from the literature were administered in a questionnaire survey to professionals with tier one construction firms and consultants. Sixty experienced construction professionals practising with tier-one construction firms and consultancy services took part in the survey. The relative importance index technique was used to rank the factors and correlation in responses of the two parties tested by the Mann-Whitney U statistics. The most critical barriers perceived by the professionals were 1) Reliance on Supervisor’s Judgement, 2) Generic and Non-Systematic Approach, 3) Variable Quality of Data and 4) Intricate Measurement Reports. Other highly ranked barriers include 5) Lack of Timely Information, 6) Laborious Data Gathering and 7) Quality Integration Constraint. The findings underpin the need to minimize dependence on subjective opinions and mere experiences of supervisors for assessment of project progress in this age of information technology. Incorporation of a level of automation into traditional progress methods will not only reduce human errors introduced into manually collected data but facilitate visualization of progress reports. Contiguous to a clear specification of the method of progress measurement in the contract document, a system that conveniently integrates cost, time and scope of work into progress measurement must be pursued. Addressing these identified critical barriers will consolidate current construction progress management practices.

A study of making use of computer-aided projection fringe system to measure breast dimension

To measure breast basic dimension by using computer-aided projection fringe system.Methods A system has been developed for measuring breast basic dimension based on computer-aided projection fringe measurement and programming software.Plastic manikins breast’s SN-N (sternal notch to nipple distance),N-ML (nipple to midline distance),N-N (internipple distance),MBW (base width of breast) and N-IMF (nipple to inframammary fold distance) are measured with this system.At the same time,these items are also measured with routine ruler.Results This study indicate that the system has some merits:① non-touching measurement;② it is very rapid,the patient measured need hold his breath only 0.5 second,and all the time it takes is about 2.5 minutes;③ the measurement’s sensitivity is as high as to 0.6 mm,which meets the clinic requirement entirely;④ the measurement’s accuracy of the system is not significantly when comparing to the routine ruler’s.Conclusion Computer-adided projection fringe system for measuring breast basic dimension is feasible and advanced.14 refs,1 fig.

A convenient look-up-table based method for the compensation of non-linear error in digital fringe projection

Although the structured light system that uses digital fringe projection has been widely implemented in three-dimensional surface profile measurement, the measurement system is susceptible to non-linear error. In this work, we propose a convenient look-up-table-based （LUT-based） method to compensate for the non-linear error in captured fringe patterns. Without extra calibration, this LUT-based method completely utilizes the captured fringe pattern by recording the full-field differences. Then, a phase compensation map is established to revise the measured phase. Experimental results demonstrate that this method works effectively.

Measuring the kinematics of a free-flying hawk-moth(Macroglossum stellatarum)by a comb-fringe projection method

We describe a 2D fringe projection method that involves projecting two groups of sharp comb fringes onto a free-flying hawk-moth from different directions and recording the images of distorted fringes by two high speed cameras from two orthogonal views. By calculating the 3D coordinates of the points on the hawk-moth and three-dimensional reconstruction of the wing, the flight trajectory, body attitude and wing kinematics including flapping angle, elevation angle, torsion angle, and camber deformation are obtained.

MULTIPARAMETER MEASUREMENT FOR RACEWAY GROOVE OF BEARING BASED ON 3D RECONSTRUCTION WITH DIGITAL STRUCTURED LIGHT

A fast 3D reconstruction method based on structured light to measure various parameters of the raceway groove is presented. Digital parallel grating stripes distributed with sine density are projected onto the raceway groove by a DLP projector, and distorting of stripes is happened on the raceway. Simultaneously, aided by three-step phase-shifting approach, three images covered by different stripes are obtained by a high-resolution CCD camera at the same location, thus a more accuracy local topography can be obtained. And then the bearing is rotated on a high precision computer controlled rotational stage. Three images are also obtained as the former step at next planned location triggered by the motor. After one cycle, all images information is combined through the mosaics. As a result, the 3D information of raceway groove can be gained. Not only geometric properties but also surface flaws can be extracted by software. A preliminary hardware system has been built, with which some geometric parameters have been extracted from reconstructed local topography.

Phase unwrapping based on deep learning in light field fringe projection 3D measurement

Phase unwrapping is one of the key roles in fringe projection three-dimensional(3D)measurement technology.We propose a new method to achieve phase unwrapping in camera array light filed fringe projection 3D measurement based on deep learning.A multi-stream convolutional neural network(CNN)is proposed to learn the mapping relationship between camera array light filed wrapped phases and fringe orders of the expected central view,and is used to predict the fringe order to achieve the phase unwrapping.Experiments are performed on the light field fringe projection data generated by the simulated camera array fringe projection measurement system in Blender and by the experimental 3×3 camera array light field fringe projection system.The performance of the proposed network with light field wrapped phases using multiple directions as network input data is studied,and the advantages of phase unwrapping based on deep learning in light filed fringe projection are demonstrated.

Remote Preparation of a Two-Particle Entangled State by a Bipartite Entangled State and a Tripartite Entangled W State

We propose a scheme to remotely prepare a general two-particle entangled state by using a bipartite entangled state and a tripartite entangled W state as the quantum channel. Our scheme consists of one sender and two remote receivers. The sender can help either one of the receivers to remotely reconstruct the original state with the assistance of the other receiver＇s single-partlcle orthogona/measurement. We obtain the total success probability and discuss the classical communication cost in our remote state preparation scheme.

Assisted Cloning and Orthogonal Complementing of an Arbitrary Unknown Two-Qubit Entangled State

Based on A.K. Pati＇s original idea [Phys. Rev. A 61 （2000） 022308] on single-qubit-state-assisted clone, very recently Zhan has proposed two assisted quantum cloning protocols of a special class of unknown two-qubit entangled states [Phys. Lett. A 336 （2005） 317]. In this paper we further generalize Zhan＇s protocols such that an arbitrary unknown two-qubit entangled state can be treated.

Remote Preparation of Three-Particle GHZ Class States

We propose a remote state preparation （RSP） scheme of three-particle Greenberger Horne-Zeilinger （GHZ） class states, where quantum channels are composed of two maximally entangled states. With the aid of forward classical bits, the preparation of the original state can be successfully realized with the probability 1/2, the necessary classical communication cost is 0.5 bit on average. If the state to be prepared belongs to some special states, the success probability of preparation can achieve 1 after consuming one extra bit on average. We then generalize this scheme to the case that the quantum channels consist of two non-maximally entangled states.

Classical Communication and Entanglement Cost in Preparing a Class of Multi-qubit States

Recently, several similar protocols [J. Opt. B 4 （2002） 380; Phys. Lett. A 316 （2003） 159; Phys. Lett. A 355 （2006） 285; Phys. Lett. A 336 （2005） 317] for remotely preparing a class of multi-qubit states （i.e, α[0...0〉 ＋β[1... 1〉） were proposed, respectively. In this paper, by applying the controlled-not （CNOT） gate, a new simple protocol is proposed for remotely preparing such class of states. Compared to the previous protocols, both classical communication cost and required quantum entanglement in our protocol are remarkably reduced. Moreover, the difficulty of identifying some quantum states in our protocol is also degraded. Hence our protocol is more economical and feasible.

Controlled Remote Preparation of a Two-Qubit State via an Asymmetric Quantum Channel

I present a new scheme for probabilistic remote preparation of a general two-qubit state from a sender to either of two receivers.The quantum channel is composed of a partial entangled tripartite Greenberger-Horne-Zeilinger (GHZ) state and a W-type state.I try to realize the remote two-qubit preparation by using the usual projective measurement and the method of positive operator-valued measure,respectively.The corresponding success probabilities of the scheme with different methods as well as the total classical communication cost required in this scheme are also calculated.

Generalized Quantum Two-Qutrit-State Splitting

A three-party scheme for splitting an arbitrary unknown two-qutrit state is proposed,where two non-maximally-entangled three-qutrit states are taken as the quantum channel among three parties.With the sender'shelp,if and only if both receivers collaborate together,they can securely share the quantum state in a probabilisticway by introducing an ancilla qutrit and performing appropriate unitary operations.The relation between the successprobability and coefficients characterizing the quantum channel is revealed.The security of the present scheme is analyzedand confirmed.Moreover,the generalization of the three-party scheme to more-party case is also sketched.

Scheme for Generalized Quantum State Sharing of a Single-Qubit State in Cavity QED

An experimentally feasible scheme for generalized quantum state sharing of an arbitrary unknown single- qubit state in cavity QED is presented. Using a generalized Greenberger-Horne-Zeilinger （GHZ） state as the quantum channel among the three parties, the quantum information （i.e. the single-qubit state） from the sender can be split in such a way that the information can be recovered if and only if both receivers collaborate. Moreover, the scheme is insensitive to both the effects of thermal field and cavity decay.

Probabilistic Remote Preparation of a Tripartite High-Dimensional Equatorial Entangled State

We present a scheme for probabilistic remote preparation of a tripartite qutrit entangled state with a partial tripartite qutrit entangled state and a partial bipartite qutrit entangled state as the quantum channel. It is found that a bipartite qutrit orthogonal projective measurement, an auxiliary qutrit particle, and the corresponding unitary transformation are required. A scheme for probabilistic remote preparation of a tripartite qudit equatorial entangled state by using a partial tripartite qudit entangled state and a partial bipartite qudit entangled state as the quantum channel is also proposed. We calculate the successful total probability and the total classical communication cost required in the RSP process, respectively.

Scheme for Cloing a Three-Particle GHZ Class State with Assistance

Our concern is to design an assisted-clone scheme which can produce a perfect copy of a three-particle Oreenberger-Horne-Zeilinger （GHZ） class state with a high probability. In the first stage of the protocol, the sender teleports the input state to the receiver by using three EPR pairs as the quantum channel. In the second stage of the protocol, a novel set of mutually orthogonal basis vectors is constructed. With the assistance of the preparer through a three-particle projective measurement under this basis, the perfect copy of an original state can be reestablished by the sender with the probability 1/2. Moreover, the classical communication cost of the scheme is also calculated.

Probabilistic joint remote preparation of a high-dimensional equatorial quantum state

This paper proposes a scheme for probabilistic joint remote preparation of an arbitrary high-dimensional equatorial quantum state by using high-dimensional single-particle orthogonal projective measurement and appropriate unitary operation. As a special case, a scheme of joint remote preparation of a single-qutrit equatorial state is presented in detail. The scheme is also generalized to the multi-party high-dimensional case. It shows that, only if when all the senders collaborate with each other, the receiver can reconstruct the original state with a certain probability.

Qinghai-Tibet Expressway experimental research

As one part of the National Highway Network Planning in China, the Qinghai-Tibet Expressway （QTE） from Golmud to Lhasa will be built in the interior of the Qinghai-Tibet Plateau （QTP） across about 630 km of permafrost lands. Due to the problematic interactions between the engineering foundations and permafrost, the frozen-soil roadbed of the QTE will be subjected to the more intense thermal disturbances due to the wider black surface. The design and construction for long-term thermal and mechanical stability will face more severe challenges than those in ordinary highways and railways in the same region. In order to provide scientific support for cold regions engineering practices, the QTE Experimental Demonstration Project （EDP） was constructed in situ in the vicinity of the Beilu＇he Permafrost Station in the interior of the QTP. In this paper, the anticipated problems of the proposed QTE project are enumerated, and the structures of the test sections for QTE EDP are described. Through numerical simulations, it was found that the heat transfer processes occurring in each specific road structure are significantly different. The heat accumulation in the highway embankment is mainly due to the black bituminous pavement, but in the railway embankment with its gravel surfaces, it mainly comes from the side slopes. As a result, the net heat accumulation of the highway embankment is three times higher than that in the railway. In expressway, the heat accumulation is further increased because of the wider pavement so that significantly more heat will be accumulated in the roadbed beneath the centerline area. Thus, the thermal stability of the fro- zen-soil roadbed and the underlying permafrost of the QTE can be seriously threatened without proper engineering measures protection against thawing. Based on research and practical experiences from the operating Qinghai-Tibet Railway （QTR） and the Qinghai-Tibet Highway （QTH）, combined with the predicted characteristics of heat transfer in an expressway embankment, nine kinds of engineering measures for mitigating the thaw settlement of foundation soils through the cooling the roadbed soils were built and are being tested in the EDP. The design of the monitoring system for the EDP and the observed parameters were also described.