No abstract

A quantum gate: A system of two coupled electron spins that is useful for simple quantum computing operations has been prepared by synthesis of a biradical 1 and co-crystallization with an isomorphous host molecule. The two weakly exchange-coupled quantum bits (target qubit blue and control qubit red) span four electron spin states. The electron spin transition is denoted by two black arrows.

We have first achieved the synthesis of triple-stranded metallo-helicates composed of 4,4':2',2'':4'',4'''-quaterimidazole (Qim) and Mn(II) or Zn(II) ions, which serve as synthetic electron spin qubits (quantum bits). In the crystal structure, a hydrogen-bonding network through counteranions and/or crystal solvents was constructed by the outward N-H hydrogen-bonding functional groups intrinsic to the imidazole skeleton. Importantly, these helicates showed high stability even in a solution state at room temperature. These salient features of triple helicates of Qim are different from those of reported metallo-helicates. These chemical properties of the Qim-based triple helicates allow us to synthesize magnetically diluted single crystals composed of Mn(II) (S = 5/2) and diamagnetic Zn(II) complexes of Qim in an appropriate Mn(II)/Zn(II) ratio. The magnetically diluted crystals can afford to build up the prototype of electron-spin qubits of Lloyd's one-dimensional periodic system, which gives a practical approach to scalable quantum computers/quantum information processing systems (QCs/QIPSs). The experiments have proven the practical capability of oligo(imidazole)s as a component of Lloyd's system which has nonequivalent g-tensors within the helicate (g-engineering). The helical symmetry plays an important role in giving a prototype of the synthetic spin qubits of the formidable Lloyd model. This result links supramolecular chemistry to the field of QCs/QIPSs.

Electrical conductivity of LiMn 2 O 4 , which is a promising cathode active material for lithium ion batteries, was monitored in situ during electrochemical lithium extraction and reinsertion reactions in 1 M LiClO 4 propylene carbonate solution. The in-situ conductivity measurement was achieved by means of an interdigitated microarray electrode coated with a uniform and dense film of LiMn 2 O 4 . The conductivity of Li 1-x Mn 2 O 4 was found to exhibit a peak-shaped profile as a function of lithium content. The conductivity of Cr 3+ -doped spinel, LiMn 1.95 -Cr 0.05 O 4 , decreased monotonically with decreasing lithium content. These results are discussed by considering the effects of phase transformation on the conductivity of these materials.