R. Landauer, "Is quantum mechanics useful?," Phil. Trans. R. Soc. Lond. A, vol. 353, pp. 367--376, 1995.  Home/Search   Document Not in Database   Summary   Related Articles   Check

.... the other polarization and thus it may not flip to the correct binary state [38] This situation is even worse in the fan out of one signal into two channels proposed by Lent et al. 34] where the cell is coupled more effectively to its successors than to its predecessor as discussed by Landauer [48]. Other questions concerning the practicality of such devices are also posed by Landauer: How do we place exactly two electrons on each cell How is that number controlled and or restored later on, in the presence of leakage, ff particles and cosmic rays Where is the compensating image charge ....

....atom relay. packing density and speed of operation but the fabrication technology has not yet reached the stage where such devices can become a reality. The SETs emerge from this comparison as the second best choice. Discussion in view of the ideal logic characteristics It was noted out before [38, 41, 48] that the wireless proposals may lack the unidirectionality property required in any logic family. A solution for this is to continuously increase the spacing between the cells in order to have a higher coupling to the left neighbor (the input) than to the right neighbor (the output) This ....

R. Landauer, "Is quantum mechanics useful?," Phil. Trans. R. Soc. Lond. A, vol. 353, pp. 367--376, 1995.

....have no obvious connection with previous gate assembly schemes. We will not touch at all on the great difficulties attendant on the actual physical realization of a quantum computer the problems of error correction[36] and quantum coherence[37, 38] are very serious ones. We refer the reader to [39] for a comprehensive discussion of these difficulties. 2 Introduction We begin by introducing some basic ideas and notation. For any unitary U = u 00 u 01 u 10 u 11 ; and m 2 f0; 1; 2; g, define the (m 1) bit (2 (m 1) dimensional) operator m (U) as m (U) jx 1 ; xm ; ....

R. Landauer, "Is quantum mechanics useful?", Proc. Roy. Soc. Lond., (to be published) .

.... down there , but in the end we are at their mercy. Even as schemes for quantum computation are being vigorously developed, common sense dictates that we explore two classes of questions: ffl Aren t there any exponential costs lurking sowhere that would offset the prospected exponential benefits[16, 17] ffl What is the fraction of problems that would benefit from quantum algorithms I wouldn t be surprised if it were a set of measure zero even though this set may contain some important problems. Most problems in combinatorial optimization are of exponential complexity, if we want an exact ....

Landauer, Rolf, "Is quantum mechanics useful?" Phil. Trans. R. Soc. London A 353 (1995), 367--376.

....factoring is much, much more remote. Still, when Peter Shor offered a wager during his seminar at Turin that the first factoring of a 500 digit number would be accomplished on a quantum computer, there were no takers on the other side. Although Rolf Landauer was not in attendance at Turin, his work[4] throughout the visionary era of quantum computing exercised an influence over much of the present work. His role has been unique during this period he has constantly challenged the visionaries to show a workable path to the future. He skeptically pointed out that abstract Turing machine ....

R. Landauer, "Is quantum mechanics useful?", Trans. Roy. Soc. Lond., in press.

....is that, even as we are asked to make a larger number of units, the individual units themselves get harder to fabricate. Fabrication plants for state of the art solid state memories now require investments on a planetary scale much as a particle supercollider and much for the same reasons[11, 28, 31]. If we ever are to attain computers consisting of an Avogadro number of devices of molecular size, some form of massively parallel fabrication and assembly will be necessary. Fortunately, when we reach the Angstrom scale the fabrication aspect of the problem disappears: atoms and certain small ....

Landauer, Rolf, "Is quantum mechanics useful?" Phil. Trans. R. Soc. London A 353 (1995), 367--376.

....another generalization, however, to multiple (interacting) quantum particles. This new system, described in Section 6, is a quantum lattice gas automaton (QLGA) and may be expected to be relevant for modelling parallel quantum architectures constructed from few electron devices. As Landauer [20] and others [21] have emphasized, achieving practical quantum computation will be difficult for a variety of reasons. The most fundamental problem is decoherence [22,23] which destroys the delicate interference phenomena on which quantum algorithms such as Shor s [5] depend. In Section 7 we ....

R. Landauer, "Is quantum mechanics useful?", Phil. Trans. Roy. Soc. Lond. A 353 (1995) 367--376.

....have no obvious connection with previous gate assembly schemes. We will not touch at all on the great difficulties attendant on the actual physical realization of a quantum computer the problems of error correction[33] and quantum coherence[34, 35] are very serious ones. We refer the reader to [36] for a comprehensive discussion of these difficulties. 2 Introduction We begin by introducing some basic ideas and notation. For any unitary U = u 00 u 01 u 10 u 11 ; and m 2 f0; 1; 2; g, define the (m 1) bit (2 (m 1) dimensional) operator m (U) as m (U) jx 1 ; xm ; yi) ....

R. Landauer, "Is quantum mechanics useful?", Proc. Roy. Soc. Lond., (to be published) .

....for a superconducting electronic embodiment of quantum computation and to offer a preliminary assessment of the magnitude of the technical challenge to achieve it. Note, however, that many knowledgeable scientists believe that useful quantum computation is next to unattainable in any technology [28], 29] ....

R. Landauer, "Is quantum mechanics useful?", Phil. Trans. R. Soc. Lond. A, vol. 353, Iss. 1703, pp. 367-376, 1995.

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