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In this study, the integrated three-in-one (temperature, humidity, and wind speed) microsensor was made through the technology of the Micro-electro-mechanical Systems (MEMS) to measure three important physical quantities of the internal environment of the cold air pipe of the Heating, Ventilation and Air Conditioning (HVAC) in the factory, plan the installation positions of the integrated three-in-one microsensor and commercially available wind speed sensor required by the internal environment of the cold air pipe, and conduct the actual 310-h long term test and comparison. In the experiment, it was also observed that the self-made micro wind speed sensor had higher stability compared to the commercially available wind speed sensor (FS7.0.1L.195). The self-made micro wind speed sensor has a variation range of ±200 mm/s, while the commercially available wind speed sensor a variation range of ±1000 mm/s. The commercially available wind speed sensor (FS7.0.1L.195) can only measure the wind speed; however, the self-made integrated three-in-one microsensor can conduct real-time measurements of temperature and humidity according to the environment at that time, and use different calibration curves to know the wind speed. As a result, it is more accurate and less costly than commercially available wind speed sensors. The material cost of self-made integrated three-in-one microsensor includes chemicals, equipment usage fees, and wires. In the future, factories may install a large number of self-made integrated three-in-one microsensors in place of commercially available wind speed sensors. Through real-time wireless measurements, the self-made integrated three-in-one microsensors can achieve the control optimization of the HVAC cold air pipe’s internal environment to improve the quality of manufactured materials.

A switchable and tunable dual-function absorber/polarization converter is presented in this work. The constitution of the structure, which incorporates patterned graphene and photosensitive silicon (Si), can minimize undesired optical losses. Simulated results show that when the Si is metallic, the structure behaves as a broadband absorption of more than 90% in the range of 1.45–3.36 THz. Its peak absorption can be tuned from 22% to 99.8% by changing the Fermi energy of graphene. Furthermore, the interference theory analyzes the physical mechanism for broadband absorption. When the Si is in the dielectric state, the structure has a transmission polarization conversion function, which realizes the conversion from linear to cross-polarized waves. The polarization conversion ratio (PCR) is greater than 90% in the 3.82–4.43 THz range. Meanwhile, the cross-polarization transmission can be dynamically tuned from 28% to 97%, and the PCR can also be tuned from 17% to 99.9% by adjusting the conductivity of the Si. The reason for realizing polarization conversion is explained by the polarization decomposition method. This study provides a design opinion of high-performance multifunctional tunable terahertz devices.

We study temperature effects on non-Markovian dynamics in a model of an atomic impurity qubit immersed in a quasi-two-dimensional dipolar Bose–Einstein condensate , which can be described as a pure dephasing spin-boson model. We use the measure proposed by Breuer et al. (Phys Rev Lett 103:210401, 2009) to characterize non-Markovianity of the quantum process and find for larger relative dipole–dipole interaction, properly low temperature can induce the non-Markovianity enhancement. We give an explanation of the non-Markovianity enhancement that raising temperature can increase the sharpness of the temperature-dependent environmental spectral density.

It has been shown that a nearly pure Greenberger–Horne–Zeilinger (GHZ) state could be distilled from a large (even infinite) number of GHZ-diagonal states that can be obtained by depolarizing general multipartite mixed states (non-GHZ-diagonal states) through sequences of (probabilistic) local operations and classical communications. We here demonstrate that perfect GHZ states can be extracted, with certain probabilities, from two copies of non-GHZ-diagonal mixed states when some conditions are satisfied. This result implies that it is not necessary to depolarize these entangled mixed states to the GHZ-diagonal type, and that they are better than GHZ-diagonal states for distillation of pure GHZ states. We find a wide class of multipartite entangled mixed states that fulfill the requirements. Moreover, we display that the obtained result can be applied to practical noisy environments, e.g., amplitude-damping channels. Our findings provide an important complementarity to conventional GHZ-state distillation protocols (designed for GHZ-diagonal states) in theory, as well as having practical applications.

It has been shown that two-photon parity check has widespread applications in optical quantum information processing. In recent years much effort has been made to implement nondestructive two-photon parity detection using cross-Kerr nonlinearity (XKNL) effect. We here put forward an XKNL-based scheme for nearly deterministic two-photon parity detection without destroying the photons, in which the required cross-Kerr phase shift could be much (even several orders of magnitude) smaller than that required for previous schemes. The scheme utilizes a ring cavity fed by a coherent state beam as a quantum information bus which interacts with one of the two path modes of two polarized photons through a cross-Kerr medium. The measurement outcome of the bus mode reveals the polarization-parity of the two photons.

We present a scheme for asymmetric quantum information splitting, where a sender distributes asymmetrically a qubit to distant agents in a network. The asymmetric distribution leads to that the agents have different powers to reconstruct the sender's qubit. In other words, the authorities of the agents for getting the quantum secret are hierarchized. The scheme does not need the agents to get together and make nonlocal operations. Our scheme can also be modified to implement controlled teleportation against uncooperation of part of supervisors., Comment: Introduction and Conclusion parts are improved

Recently, Yeo and Chua introduced a genuine four-qubit entangled state | χ 〉 which can implement perfect teleportation of an arbitrary two-qubit state [Y. Yeo, W.K. Chua, Phys. Rev. Lett. 96 (2006) 060502]. It has been shown that the state | χ 〉 is inequivalent to the well-known Greenberger–Horne–Zeilinger state, W state, and linear cluster state, in terms of stochastic local operations and classical communication [C.F. Wu, Y. Yeo, L.C. Kwek, C.H. Oh, Phys. Rev. A 75 (2007) 032332]. This “new” class of state has many interesting entanglement properties and possible applications in quantum-information processing and fundamental tests of quantum mechanics. Here, we propose a simple scheme to generate the state | χ 〉 in cavity quantum electrodynamics. Our idea may be helpful for in-depth study on such a class of state and its practical applications.

Two schemes are proposed for generating atomic qubits cluster states in cavity quantum electrodynamics (QED). In the first scheme, only two-atom–cavity interactions are involved, and cluster states can be directly generated by using constructed two-qubit controlled phase gates. The second scheme needs the assistance of additional single-qubit rotations, but takes less time than the first one for two-atom operations in the cavity. In this scheme, two projective operators are constructed to prepare two-dimension or more complicated configurations of cluster states. Both schemes are insensitive to the cavity decay due to the fact that the cavity is only virtually excited during the interaction between atoms and the cavity. The idea can also be applied to the ion trap system.

A direct entanglement concentration protocol for generalized GHZ states is proposed using entanglement swapping in cavity QED. Via this scheme, multi-atom maximally entangled states can be prepared free from the effects of the cavity decay and the thermal field, due to the fact that the interaction here is a large-detuned one between atoms and the cavity.

A simple scheme is presented for generating four-photon Greenberger-Horne-Zeilinger (GHZ) states with interaction between a four-level atom and two bimodal cavities. In the proposed protocol, the quantum information is encoded on Fock states of the cavity fields. The detection of the atom can collapse the cavity to the desired state. The experimental feasibility of our proposal is also discussed.

This paper is to investigate the effects of quantum noises on entanglement localization by taking an example of reducing a three-qubit Greenberger-Horne-Zeilinger (GHZ) state to a two-qubit entangled state. We consider, respectively, two types of quantum decoherence, i.e., amplitude-damping and depolarizing decoherence, and explore the best von Neumann measurements on one of three qubits of the triple GHZ state for making the amount of entanglement of the collapsed bipartite state be as large as possible. The results indicate that different noises have different impacts on entanglement localization, and that the optimal strategy for reducing a three-qubit GHZ state to a two-qubit one via local measurements and classical communications in the amplitude-damping case is different from that in the noise-free case. We also show that the idea of entanglement localization could be utilized to improve the quality of bipartite entanglement distributing through amplitude-damping channels. These findings might shed a new light on entanglement manipulations and transformations., 8 pages, 8 figures

Remote information concentration (RIC) in $d$-level systems (qudits) is studied. It is shown that the quantum information initially distributed in three spatially separated qudits can be remotely and deterministically concentrated to a single qudit via an entangled channel without performing any global operations. The entangled channel can be different types of genuine multipartite pure entangled states which are inequivalent under local operations and classical communication. The entangled channel can also be a mixed entangled state, even a bound entangled state which has a similar form to the Smolin state, but has different features from the Smolin state. A common feature of all these pure and mixed entangled states is found, i.e., they have $d^2$ common commuting stabilizers. The differences of qudit-RIC and qubit-RIC ($d=2$) are also analyzed., Comment: 10 pages, 3 figures

We propose a scheme for multiparty hierarchical quantum-information splitting (QIS) with a multipartite entangled state, where a boss distributes a secret quantum state to two grades of agents asymmetrically. The agents who belong to different grades have different authorities for recovering boss's secret. Except for boss's Bell-state measurement, no nonlocal operation is involved. The presented scheme is also shown to be secure against eavesdropping. Such a hierarchical QIS is expected to find useful applications in the field of modern multipartite quantum cryptography., Comment: 6 pages, 2 tables

The cross-Kerr nonlinearity (XKNL) effect can induce efficient photon interactions in principle with which photonic multiqubit gates can be performed using far fewer physical resources than linear optical schemes. Unfortunately, it is extremely challenging to generate giant cross-Kerr nonlinearities. In recent years, much effort has been made to perform multiqubit gates via weak XKNLs. However, the required nonlinearity strengths are still difficult to achieve in the experiment. We here propose an XKNL-based scheme for realizing a two-photon polarization-parity gate, a universal two-qubit gate, in which the required strength of the nonlinearity could be orders of magnitude weaker than those required for previous schemes. The scheme utilizes a ring cavity fed by a coherent state as a quantum information bus which interacts with a path mode of the two polarized photons (qubits). The XKNL effect makes the bus pick up a phase shift dependent on the photon number of the path mode. Even when the potential phase shifts are very small they can be effectively measured using photon-number resolving detectors, which accounts for the fact that our scheme can work in the regime of tiny XKNL. The measurement outcome reveals the parity (even parity or odd parity) of the two polarization qubits., Comment: 8 pages, 5 figures; some revisions have been made

We study the ancilla-free $1\ensuremath{\rightarrow}2$ phase-covariant telecloning for qudits. We show that the fidelity of the two clones can probabilistically reach that of the clones in the optimal $1\ensuremath{\rightarrow}2$ phase-covariant cloning (involving an ancilla). More interestingly, that can realize the above nonlocal cloning tasks are suitable nonmaximally entangled states rather than the maximally entangled states.

Recently, a genuine four-qubit entangled state ${\ensuremath{\mid}{\ensuremath{\chi}}^{00}⟩}_{3214}$ has been proposed [Y. Yeo and W. K. Chua, Phys. Rev. Lett. 96, 060502 (2006)]. This state has many interesting entanglement properties and possible applications in quantum information processing and fundamental tests of quantum physics. Here we present a simple scheme for generating such a state in an ion-trap system. We also demonstrate how to discriminate between the 16 basis states ${{\ensuremath{\mid}{\ensuremath{\chi}}^{ij}⟩}_{3214}={\ensuremath{\sigma}}_{3}^{i}{\ensuremath{\sigma}}_{1}^{j}{\ensuremath{\mid}{\ensuremath{\chi}}^{00}⟩}_{3214},i,j=0,1,2,3}$.