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A single-molecule magnet is a long-sought-after nanoscale component because it can enable miniaturized nonvolatile memory storage devices. The signature of a singlemolecule magnet is switching between two bistable magnetic ground states under an external magnetic field. Based on this feature, we theoretically investigated a magnetic-field-controlled reversible resistance changes active at low temperatures in a molecular magnetic tunnel junction, which consists of a single-molecule magnet sandwiched between one ferromagnetic electrode and one normal metal electrode. Our numerical results demonstrate that the molecular magnetism orientation can be manipulated by magnetic fields to be parallel/antiparallel to the ferromagnetic electrode magnetization. Moreover, the different magnetic configurations can be ”read out” based on different resistance states or different spin polarization parameters in the current spectrum, even in the absence of a magnetic field. Such an external magnetic field-controlled resistance state switching effect is similar to that in traditional spin valve devices. The difference between the two systems is that one of the ferromagnetic layers in the original device has been replaced by a magnetic molecule. This proposed scheme provides the possibility of better control of the spin freedom of electrons in molecular electrical devices, with potential application in future high-density nonvolatile memory devices.

We theoretically propose an all-electrically controlled spin-current diode consisting of a quantum dot sandwiched between one normal electrode and one ferromagnetic electrode. By applying a spin bias V S across one electrode, the spin current distribution shows a rectification effect; that is, in the forward spin bias regime, a spin current can tunnel through the junction, while in the reverse bias regime, the current is tiny. Such asymmetry in the spin-current profile suggests diode-like behaviour with respect to the spin bias. Moreover, the polarity direction of this spin-current diode can be manipulated and reversed by adjusting the gate voltage, which is much more feasible than the approach with traditional charge-current diodes. The present device can be realized by current technologies and has potential applications in spintronics or quantum information processing.

A magnetic field-controlled spin-current diode is theoretically proposed, which consists of a junction with an interacting quantum dot sandwiched between a pair of nonmagnetic electrodes. By applying a spin bias V S across the junction, a pure spin current can be obtained in a certain gate voltage regime,regardless of whether the Coulomb repulsion energy exists. More interestingly, if we applied an external magnetic field on the quantum dot, we observed a clear asymmetry in the spectrum of spin current I S as a function of spin bias, while the charge current always decays to zero in the Coulomb blockade regime. Such asymmetry in the current profile suggests a spin diode-like behavior with respect to the spin bias, while the net charge through the device is almost zero. Different from the traditional charge current diode, this design can change the polarity direction and rectifying ability by adjusting the external magnetic field, which is very convenient. This device scheme can be compatible with current technologies and has potential applications in spintronics or quantum processing.

In order to make full use of natural resources and ensure the safety of the ship navigation, based on the self-designed ship trajectory tracking system, the self-propelled model test of ship maneuverability which include cycle test and zig-zag test under the combined effects of water and fluid mud was completed in the test pool. And then based on the results of the tests, the influences of under-keel clearance on ship resistance, heading stability and turning radius were analyzed, and the maneuverability of the ship’s navigation in the fluid mud was comprehensively evaluated. The results show that as the under-keel clearance decreases, the linear stability of the ship increases, but its maneuverability deteriorates. In order to ensure safety, the depth of ship dragging into the fluid mud must be less than 10% of ship’s draft.

This paper considers the teleportation of quantum controlled-Not (CNOT) gate by using partially entangled states. Different from the known probability schemes, it presents a method for teleporting a CNOT gate with unit fidelity and unit probability by using two partially entangled pairs as quantum channel. The method is applicable to any two partially entangled pairs satisfying the condition that their smaller Schmidt coefficients μ and v are (2μ + 2v – 2μv – 1) ≥ 0. In this scheme, the sender's local generalized measurement described by a positive operator valued measurement (POVM) lies at the heart. It constructs the required POVM. It also puts forward a scheme for teleporting a CNOT with two targets gate with unit fidelity by using same quantum channel. With assistance of local operations and classical communications, three spatially separated users are able to complete the teleportation of a CNOT with two targets gate with probability of (2μ + 2v – 1). With a proper value of μ and v, the probability could reach nearly 1.

We present a new method called the permutation matrix method to perform dense coding using Greenberger–Horne–Zeilinger (GHZ) states. We show that this method makes the study of dense coding systematically and regularly. It also has high potential to be realized physically.

Remote quantum-state discrimination is a critical step for the implementation of quantum communication network and distributed quantum computation. We present a protocol for remotely implementing the unambiguous discrimination between nonorthogonal states using quantum entanglements, local operations, and classical communications. This protocol consists of a remote generalized measurement described by a positive operator valued measurement (POVM). We explicitly construct the required remote POVM. The remote POVM can be realized by performing a nonlocal controlled-rotation operation on two spatially separated qubits, one is an ancillary qubit and the other is the qubit which is encoded by two nonorthogonal states to be distinguished, and a conventional local Von Neumann orthogonal measurement on the ancilla. The particular pair of states that can be remotely and unambiguously distinguished is specified by the state of the ancilla. The probability of successful discrimination is not optimal for all admissible pairs. However, for some subset it can be very close to an optimal value in an ordinary local POVM.

We present the generation of six-particle Greenberger–Horne–Zeilinger (GHZ) states via deterministic entanglement concentration and generalize the scheme to the case of 2N particles. We show that arbitrary 2N-particle GHZ states can be obtained with certain probability via entanglement concentration. This may provide a new perspective for the preparation of multi-particle GHZ states. This study is also an exploration on the theory of deterministic entanglement concentration.

We present a systematic simple method to implement a generalized quantum control-NOT (CNOT) gate on two d-dimensional distributed systems. First, we show how the nonlocal generalized quantum CNOT gate can be implemented with unity fidelity and unity probability by using a maximally entangled pair of qudits as a quantum channel. We also put forward a scheme for probabilistically implementing the nonlocal operation with unity fidelity by employing a partially entangled qudit pair as a quantum channel. Analysis of the scheme indicates that the use of partially entangled quantum channel for implementing the nonlocal generalized quantum CNOT gate leads to the problem of 'the general optimal information extraction'. We also point out that the nonlocal generalized quantum CNOT gate can be used in the entanglement swapping between particles belonging to distant users in a communication network and distributed quantum computer.

High-dimensional, frequency-entangled photonic quantum bits (qudits for d-dimension) are promising resources for quantum information processing in an optical fiber network and can also be used to improve channel capacity and security for quantum communication. However, up to now, it is still challenging to prepare high-dimensional frequency-entangled qudits in experiments, due to technical limitations. Here we propose and experimentally implement a novel method for a simple generation of frequency-entangled qudts with without the use of any spectral filters or cavities. The generated state is distributed over 15 km in total length. This scheme combines the technique of spectral engineering of biphotons generated by spontaneous parametric down-conversion and the technique of spectrally resolved Hong-Ou-Mandel interference. Our frequency-entangled qudits will enable quantum cryptographic experiments with enhanced performances. This distribution of distinct entangled frequency modes may also be useful for improved metrology, quantum remote synchronization, as well as for fundamental test of stronger violation of local realism.

The stripe-shaped domain (SSD) structure was prepared in the initial ferroelectric liquid crystal (FLC) alignment without the application of an external electric field, which was realized by the aligning layer modification through the doping of tin tetra-2, 4-dimethyl phenoxy phthalocyanine (SnPc) into the rubbed polyimide films. Atomic force microscopy was used to investigate the alignment films and the corresponding aligning ability was evaluated through the pre-tilt angle measurement. The memory capability and the contrast ratio of thus aligned SSFLC cells have been enhanced and improved with the appearance of the SSD structure. The electrically controlled 64 × 64 FLC spatial light modulator was fabricated using the improved aligning method, which proves valuable for the practical device fabrication.

We present general and optimal schemes for local conversion of pure states, via one specific example. First, we give the general solution of the doubly stochastic matrix. Then, we find the general and optimal positive-operator-valued measure (POVM) to realize the local conversion of pure states. Lastly, the physical realization of the POVM is discussed. We show that our scheme has a more general and better effect than other schemes.

Twenty-five new R-branch lines of the v2 (1−←0+) band of H3O+ are measured using diode laser velocity modulation spectroscopy between 1070 and 1230 cm−1. The H3O+ ions are produced in a high voltage ac discharge with water diluted in helium. The observed lines together with all the previously published measurements are fit to the standard vibration-rotational Hamiltonian of an oblate symmetric top, yielding a set of improved molecular constants. All the sextic centrifugal distortion constants for both 0+ and 1− states are determined precisely. The observed R(13,0) transition is shifted about -0.129 cm−1 from its calculated value, indicating that a near degeneracy exists between the (13, 0)+ and (13, 3)− ground-state rotation-inversion levels.

We first present the general solution and the simplest special solution of the doubly stochastic matrix used in deterministic entanglement concentration. Then, we give a better scheme to realize deterministic entanglement concentration. Under this scheme, the concentration is realized, and more importantly, two partially entangled pairs concentrate to four-particle Greenberger–Horne–Zeilinger (GHZ) states with a certain probability.

(Fe50Co25B15Si10)80Cu20 ribbons are prepared by using the single-roller melt-spinning method. A dual-layer structure consisting of a (Fe, Co)-rich amorphous phase and a Cu-rich crystalline phase forms due to metastable liquid phase separation before solidification. The magnetic hysteresis loops of the as-quenched and annealed samples are measured at room temperature. It is indicated that the coercivity of the ribbon is almost zero in the as-quenched state. The crystallization leads to the increase of coercivity and decrease of saturation magnetization.