Narrow Results

An enzyme system organized in a flow device with three parallel channels was used to mimic a reversible Double Feynman Gate (DFG) with three input and three output signals. Reversible conversion of NAD⁺ and NADH cofactors was used to perform XOR logic operations, while biocatalytic oxidation of NADH resulted in Identity operation working in parallel. The first biomolecular realization of a DFG gate is promising for integrating into complex biomolecular networks operating in future unconventional biocomputing systems, as well as for novel biosensor applications.

We propose AND and OR logic gates based on a phononic crystal (PNC) ring resonator cavity. The proposed devices consist of ring resonator cavities coupled to PNC line defect waveguides. The logic gate performance has been analyzed and investigated using finite element methods. The design specifies a logical 0 as a transmission rate of 0.3 or less and a logical 1 as a transmission rate of 0.6 or more. The results show that such a design has stable transmission peaks, meeting the requirements of acoustic logic gates. The design has the potential to be a key component in future phononic integrated circuits.

There is a special class of logic gates, called universal gates, any one of which is sufficient to express any desired computation. The NAND gate is truly global, given that it is already known, each Boolean function can be represented in a circuit that contains only NOT and AND gates, it is sufficient to show that these gates can be defined from the NAND gate. The effect of Rashba spin-orbit interaction (SOI) on the gate response and spin current density in a series of non-interacting one-dimensional rings connected to some leads is studied theoretically within the waveguide theory. The gates response and spin current density are computed in geometry of the system containing two terminal double quantum rings. Also, the presence and absence of Rashba SOI are treated as the two inputs of the AND/NAND/NOT gates. Furthermore, simulation of the device performance demonstrates that vital improvement toward spintronic applications can be achieved by optimizing device parameters such as magnetic flux and Rashba coefficient.

When signum operation is applied in chaotic systems to realize piecewise-linearity, the original nonlinearity turns to be a kind of Boolean calculation, and correspondingly the chaotic circuit can be implemented by an analog structure embedded with some logic-gate circuits. In this paper, as examples based on the diffusionless Lorenz system we proposed a couple of chaotic flows with signum piecewise-linearity, which experimentally resorts to digital gate circuits. The experimental chaotic circuit with logic elements was built, and the oscillation in the physical circuit agrees well with the numerical simulation.

A series of simple logic gates based on a water-soluble porphyrin molecule, 5,10,15,20-tetrakis-(4-sulfonatophenyl)porphyrin (TPPS₄) is designed. Logic operations, including OR, NOR, INHIBIT and AND, have been built by two inputs of acid/base or metal ions (Al³⁺ and/or Sn⁴⁺) and two outputs of UV-vis absorption and fluorescent spectra. An OFF–ON switch triggered by Al³⁺ ion in vitro is developed based on TPPS₄.

A julolidine-based boron-phenylpyrrin small molecule has been designed and synthesized through a one-pot condensation-complexation procedure. Systematic optical studies show that this compound displays two distinct optical responses to the addition of HCl and Fe${}^{\mathrm{\text{3+}}}$ in succession: the addition of HCl induces an obvious red shift in its maximum absorption and fluorescence emission bands accompanied with the fluorescence quenching, whereas after synchronously adding H${}^{\mathrm{\text{+}}}$ and Fe${}^{\mathrm{\text{3+}}}$, the maximum absorption and fluorescence emission wavelength were found to shift little but with an obvious decrease in the absorbance and fluorescence intensity, suggesting the dual-detecting nature of this compound to H${}^{\mathrm{\text{+}}}$ and Fe${}^{\mathrm{\text{3+}}}$ under acid conditions. More interestingly, based on the HCl/Fe${}^{\mathrm{\text{3+}}}$-mediated absorption and fluorescence signal features, JBPP can function as AND, NAND, INH and IMP logic gates which can be further developed into a 2:4 digital demultiplexer These will endow this small molecule compound with great potential for applications in molecular logic material, chemosensors and biological fields.

A mathematical model of classical computer was invented by Alan Turing and named “Turing machine” model, which is an idealized computer with a simple set of instructions and infinite memories. Soon after Turing’s model was proposed, John von Neumann developed a theoretical model for how to implement all the components in a computer to be fully capable as a Turing machine. In more practical way, we will make use of the circuit model, which is useful also in the study of quantum computation. A circuit may involve many inputs, outputs, many wires and many logic gates. These circuits will be implemented by semi-conductors, which have two functions as conductor and insulator and acts under given conditions as a high-speed switch that leads and stops electricity. Modern computers such as personal computers (PC) use integrated circuits (IC) of semiconductor. While the peculiar feature of semiconductor is based entirely on physics of quantum mechanics, we do not call these computers “quantum computers” but rather called “classical computers”, because logic gates are based on binary representations and any quantum state of atom or molecule is not used as a logic gate: in classical computers, the data are represented by two logical values 0 and 1 in the circuits using devices with high voltage/low voltage, current on/off, and/or direction of magnetization up/down.

The following sections are included:

• Turing machine

• von Neumann computer

• Possibility and complexity of computation
  • Arithmetic operations
    • P problem
  • Factorization and decision of prime numbers
    • About the NP problem
  • Combination problem
    • NP-complete problems
  • Computational complexity and amount of computation

• Logic gates

• Logic circuits

• Sequential circuit and memory

• Problem