Controlled quantum teleportation and secure direct communication

We present a controlled quantum teleportation protocol. In the protocol, quantum information of an unknown state of a 2-level particle is faithfully transmitted from a sender (Alice) to a remote receiver (Bob) via an initially shared triplet of entangled particles under the control of the supervisor Charlie. The distributed entangled particles shared by Alice, Bob and Charlie function as a quantum information channel for faithful transmission. We also propose a controlled and secure direct communication scheme by means of this teleportation. After insuring the security of the quantum channel, Alice encodes the secret message directly on a sequence of particle states and transmits them to Bob supervised by Charlie using this controlled quantum teleportation. Bob can read out the encoded message directly by the measurement on his qubit. In this scheme, the controlled quantum teleportation transmits Alice's message without revealing any information to a potential eavesdropper. Because there is not a transmission of the qubit carrying the secret message between Alice and Bob in the public channel, it is completely secure for controlled and direct secret communication if perfect quantum channel is used. The feature of this scheme is that the communication between two sides depends on the agreement of the third side.Comment: 4 page

Surface phase separation in nanosized charge-ordered manganites

Recent experiments showed that the robust charge-ordering in manganites can be weakened by reducing the grain size down to nanoscale. Weak ferromagnetism was evidenced in both nanoparticles and nanowires of charge-ordered manganites. To explain these observations, a phenomenological model based on surface phase separation is proposed. The relaxation of superexchange interaction on the surface layer allows formation of a ferromagnetic shell, whose thickness increases with decreasing grain size. Possible exchange bias and softening of the ferromagnetic transition in nanosized charge-ordered manganites are predicted.Comment: 4 pages, 3 figure

Searching for high-KK isomers in the proton-rich A∼80A\sim80 mass region

Configuration-constrained potential-energy-surface calculations have been performed to investigate the $K$ isomerism in the proton-rich $A\sim80$ mass region. An abundance of high-$K$ states are predicted. These high-$K$ states arise from two and four-quasi-particle excitations, with $K^{\pi}=8^{+}$ and $K^{\pi}=16^{+}$, respectively. Their excitation energies are comparatively low, making them good candidates for long-lived isomers. Since most nuclei under studies are prolate spheroids in their ground states, the oblate shapes of the predicted high-$K$ states may indicate a combination of $K$ isomerism and shape isomerism

Effect of iron on the microstructure and mechanical property of Al-Mg-Si-Mn and Al-Mg-Si diecast alloys

This article is made available through the Brunel Open Access Publishing Fund. Copyright @ 2012 Elsevier B.V.This article has been made available through the Brunel Open Access Publishing Fund.Al–Mg–Si based alloys can provide super ductility to satisfy the demands of thin wall castings in the application of automotive structure. In this work, the effect of iron on the microstructure and mechanical properties of the Al–Mg–Si diecast alloys with different Mn concentrations is investigated. The CALPHAD (acronym of Calculation of Phase Diagrams) modelling with the thermodynamic properties of the multi-component Al–Mg–Si–Mn–Fe and Al–Mg–Si–Fe systems is carried out to understand the role of alloying on the formation of different primary Fe-rich intermetallic compounds. The results showed that the Fe-rich intermetallic phases precipitate in two solidification stages in the high pressure die casting process: one is in the shot sleeve and the other is in the die cavity, resulting in the different morphologies and sizes. In the Al–Mg–Si–Mn alloys, the Fe-rich intermetallic phase formed in the shot sleeve exhibited coarse compact morphology and those formed in the die cavity were fine compact particles. Although with different morphologies, the compact intermetallics were identified as the same α-AlFeMnSi phase with typical composition of Al24(Fe,Mn)6Si2. With increased Fe content, β-AlFe was found in the microstructure with a long needle-shaped morphology, which was identified as Al13(Fe,Mn)4Si0.25. In the Al–Mg–Si alloy, the identified Fe-rich intermetallics included the compact α-AlFeSi phase with typical composition of Al8Fe2Si and the needle-shaped β-AlFe phase with typical composition of Al13Fe4. Generally, the existence of iron in the alloy slightly increases the yield strength, but significantly reduces the elongation. The ultimate tensile strength maintains at similar levels when Fe contents is less than 0.5 wt%, but decreases significantly with the further increased Fe concentration in the alloys. CALPHAD modelling shows that the addition of Mn enlarges the Fe tolerance for the formation of α-AlFeMnSi intermetallics and suppresses the formation of β-AlFe phase in the Al–Mg–Si alloys, and thus improves their mechanical properties.EPSRC and JL

Effect of iron on the microstructure and mechanical property of Al-Mg-Si-Mn and Al-Mg-Si diecast alloys

This article is made available through the Brunel Open Access Publishing Fund. Copyright @ 2012 Elsevier B.V.This article has been made available through the Brunel Open Access Publishing Fund.Al–Mg–Si based alloys can provide super ductility to satisfy the demands of thin wall castings in the application of automotive structure. In this work, the effect of iron on the microstructure and mechanical properties of the Al–Mg–Si diecast alloys with different Mn concentrations is investigated. The CALPHAD (acronym of Calculation of Phase Diagrams) modelling with the thermodynamic properties of the multi-component Al–Mg–Si–Mn–Fe and Al–Mg–Si–Fe systems is carried out to understand the role of alloying on the formation of different primary Fe-rich intermetallic compounds. The results showed that the Fe-rich intermetallic phases precipitate in two solidification stages in the high pressure die casting process: one is in the shot sleeve and the other is in the die cavity, resulting in the different morphologies and sizes. In the Al–Mg–Si–Mn alloys, the Fe-rich intermetallic phase formed in the shot sleeve exhibited coarse compact morphology and those formed in the die cavity were fine compact particles. Although with different morphologies, the compact intermetallics were identified as the same α-AlFeMnSi phase with typical composition of Al24(Fe,Mn)6Si2. With increased Fe content, β-AlFe was found in the microstructure with a long needle-shaped morphology, which was identified as Al13(Fe,Mn)4Si0.25. In the Al–Mg–Si alloy, the identified Fe-rich intermetallics included the compact α-AlFeSi phase with typical composition of Al8Fe2Si and the needle-shaped β-AlFe phase with typical composition of Al13Fe4. Generally, the existence of iron in the alloy slightly increases the yield strength, but significantly reduces the elongation. The ultimate tensile strength maintains at similar levels when Fe contents is less than 0.5 wt%, but decreases significantly with the further increased Fe concentration in the alloys. CALPHAD modelling shows that the addition of Mn enlarges the Fe tolerance for the formation of α-AlFeMnSi intermetallics and suppresses the formation of β-AlFe phase in the Al–Mg–Si alloys, and thus improves their mechanical properties.EPSRC and JL

Codebook Based Minimum Subspace Distortion Hybrid Precoding for Millimeter Wave Systems

© 2018 IEEE. Hybrid precoding is adopted for millimeter wave (mmWave) communications to offer a good trade-off between hardware complexity and system performance. In this paper, we investigate a codebook based hybrid precoder for single-user mmWave systems with large antenna arrays. We exploit the sparse nature of mmWave channels to transform the hybrid precoding design problem into a vector space distortion optimization problem which is only related to the radio frequency (RF) precoder. A near optimal solution for the RF optimization problem is derived with the assumption of the perfect channel state information (CSI) at the transmitter, which is practically very difficult to obtain. To reduce the requirement of the CSI at the transmitter, we propose the codebook based minimum subspace distortion (MSD) hybrid precoding algorithm, which obtains CSI at the combiner side and returns the index of optimal RF codewords and the baseband precoder through a limited feedback channel. Simulation results are provided and validate the effectiveness of our proposed hybrid precoding algorithm