Cold trapped ions

P. Zoller, Quantum computations with cold trapped ions, Phys. Rev. Lett. 74, 4091 (1995). 

Cold Trapped Ions Project, JST, University of Electrocommunications,... 

This work is supported by the UK National Measurement System (NMS) under the Foundation Programme project 4.2 Hydrogenic systems calculable frequency standards . The measurement of the 2S Lamb shift in Si13+ is also a key experiment in a five-year International Collaborative Research Project (ICORP) on Cold Trapped Ions between NPL, the University of Oxford and the Japan Science and Technology Corporation (JST). 

National Physical Laboratory, Teddington, Middlesex TWll OLW, UK Department of Physics, University of Oxford, Oxford, 0X1 3PU, UK Cold Trapped Ions Project, JST, University of Electrocommnnications,... 

James, D.F.V. Quantum dynamics of cold trapped ions with apphcation to quantum computation. AppZ. Phys. B. 1998, 66, 181-190. 

Many systems are being studied to manipulate quantum information. Some make use of individual atoms cold trapped ions, neutral atoms in optical lattices, atoms in crystals. Other involve particle spins or photons in cavity QED or nonlinear optical setups as well as more exotic ones where geometric combinations of elementary excitations are defined as qubits, such as in topological quantum computing [8]. However, none of these systems has yet emerged as a definitive way to build a quantum information processor. A reason for this is that there is an essential dichotomy we need... 

Fig. 3.15. Schematic diagram of the Atomic Beam 22-Pole Trap Apparatus (AB-22PT). This instrument has been developed for exposing cold trapped ions to an effusive beam of H atoms. The velocity distribution of the hydrogen beam depends on the temperature of the accommodator and the transmission features of the two hexapole magnets. A short description of this setup has been given recently.A detailed documentation of this sophisticated instrument is in preparation. ...

Here, we will review some of the ideas given by Lloyd in [27] since they have very general applicability. They may be applied to quantum computers realized on polymers, on arrays of cold trapped ions, and on arrays of quantum dots. The example of computation on a heteropolymer will be discussed. The generalization to computation on the other systems is self-evident. 

The shift of information is quite difficult on polymers. If it were possible to shine light not on the whole polymer but on certain molecules only, simple exchange operations between the bits of two adjacent molecules would suffice. But of course this is not possible. However, cold trapped ions in multimodal electromagnetic fields that interact by Coulomb forces are a few micrometers apart. Nowadays, exciting a single one of these ions with a very well focussed laser is possible [31]. It is even possible to maintain quantum coherence in such systems for several seconds [34]. Therefore it could be that the first quantum computer will be realized on cold trapped ions. 

Urine As Multiple ion detection. Hydride generation heptane cold trap, Extraction Inorganic, monomethyl-, dimethyl- and trimethylarsenic compounds were detected by this combination of techniques 8o)... 

It is assumed that cold traps prevent these gases from passing through the trap. Unfortunately this is only partly true. The ion gauge and field... 

The rates of production of the heat evolved when a dose of carbon monoxide interacts with NiO(250) containing either 0 (ads) ions (Reaction 4) or C(V(ads) ions (Reaction 2) are given as a function of time in Figure 6. In both cases, the same amount of carbon monoxide has been introduced previously to this particular dose. Thermochemical cycles and direct observation of the presence of carbon dioxide in the cold trap confirm that, during the interaction of this particular dose of CO, carbon dioxide is desorbed to the gas phase. 

The choice of the proper stationary and mobile phases for the foregoing purpose would depend on several factors, such as the nature (polarity, stability in mobile phase) of the NOC analyzed and the availability/compatibility of the detector used. For example, if only a TEA is available as a detector, the use of an ion-exchange or a reversed-phase system is ruled out, because both require aqueous mobile phase for proper operation. Moisture in the mobile phase causes freeze-up of the cold traps in the TEA and also results in noisy response due to interference during chemiluminescence detection. Similarly, if one is using, as the detector the newly developed Hi-catalyzed denitrosation-TEA (62) or the photolytic cleavage-TEA (58), a reversed-phase system using aqueous mobile phase would be the method of choice. These detectors, however, have not been demonstrated to work in the normal-phase system. The use of an electrochemical detector will also be incompatible with an organic solvent as the mobile phase. 

The compounds resulting from the reaction of 748 were characterized by HRMS directly coupled to the reactor. The stable products 750 and 751 were analysed by GC and 111 NMR spectroscopy. The formation of the cyclodisilazane 750 is explained by dimerization of the unstable silanimine 749 only in the cold trap, as the reaction is carried out under high dilution conditions (equation 247). It was also shown that the hydrogen chloride elimination did not occur in the ion source of the mass spectrometer. 

Maher [6] has described a method for the determination of down to O.Olmg/kg of organoarsenic compounds in marine sediments. In this procedure, the organoarsenic compounds are separated from an extract of the sediment by ion exchange chromatography, and the isolated organoarsenic compounds are reduced to arsines with sodium borohydride and collected in a cold trap. Controlled evaporation of the arsine fractions and detection by atomic absorption spectrometry completes the analysis. 

In order to improve the signal-to-noise ratio in collinear laser spectroscopy, an ion source with bunched beam release was tested successfully. For this purpose, the temperature of a cold trap" inside the ion source is reduced for storage of reaction products, which are released from the trap during a subsequent period of increased temperature. The release of indium was found to occur with a FWHM of approximately 0.5s, corresponding to a... 

Jansen and co-workers [97] have described on-line TD-GC-FTIR. In the TD-GC-FTIR system a thermal desorption (TD) cold trap injector is used for the temperature-controlled outgassing of the samples with a maximum temperature of 350 °C. The volatile components are transferred to the cold trap by the carrier gas and preconcentrated. After completion of the outgassing process the cold trap is heated very quickly, causing on-column injection of the trapped components onto the gas chromatograph. The technique has recently been extended to include an ion-trap MS. 

The reaction of either cis- or trans-1 with potassium /-butoxide in tetrahydrofuran at 25 °C leads to a /-butyl ether (2), apparently arising by attack of /-butoxide ion on an intermediate l,4-di-/-butylmethylenecyclopropene. If the reaction is carried out at low temperature and the volatile materials are distilled directly into a cold trap, the cyclopropene can be trapped, albeit in low yield (10 %), by added cyclopentadiene or detected directly by low-temperature NMR23. In a related example, a l,l-dihalo-2-bromo-3-methylcyclopropane (2a) leads to products which are also apparently derived through an intermediate 1 -chloro-3-methylenecyclopropene which undergoes nucleophilic addition (See Ref. 80). 

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