Photonic logic gates

Fluorescent-labelled oligonucleotides have been applied to the development of photonic logic gates,which may have application in molecular computation. A machine which undergoes extension-contraction motion is described, which is monitored by FRET, between a duplex and a quadruplex structure. The motion is driven by the addition of single-stranded oligonucleotide that causes the quadruplex to collapse and leads to a duplex structure. 

Figure 2. Realization of optical CPHASE logic gate between two single-photon qubits, using polarizing beam-splitters (PBS), A/4 plates and 7r cross-phase modulation (XPM) studied here.

The use of molecular switches in solution phase has recently received attention (de Silva et al., 1997). Photochemical logic gates shown AND, OR, XOR, NOR, and INH functionality have been reported, whereas electrochemical storage of information via electroswitchable systems (Katz et al., 2004), electrochemical transduction of photonically or electrochemically encoded information, and electrochemi-cal/photochemical information processing (Willner et al., 2001 Perez-Inestrosa... 

By adding a logic gate between the discriminator and the counter, single-photon pulses can be counted within narrow time intervals. The principle is shown in Fig. 2.2. 

Yoshida, W., Yokobayashi, Y. (2007). Photonic boolean logic gates based on DNA aptamers. Chem Commun 2, 195-197. 

Straight SD, LiddeU PA, Moore TA, TerazonoY, Moore AL, Gust D (2007) AU-photonic molecular XOR and NOR logic gates based on photochemical control of fluorescence in a fulgimide— porphyrin-dithienylethene triad. Adv Fund Mater 17 777-785. doi 10.1002/adfin.200600802... 

The enabled OR - another type of gate that requires a minimum of three inputs -has just become available. Figure 15 shows the equivalent electronic representation, with the appropriate connection of AND and OR gates. In this context we note that the INHIBIT gate discussed in Section 11.10 also involves an enabling/disabling input. One strand of Pina, Maestri, and Balzani s novel exploitation of flavylium derivative photochemistry was briefly mentioned in Section 11.4. This AND logic system used protons and ultraviolet photons as the two inputs, to create a visible... 

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