Quantum-dot cellular automata using buried dopants

Abstract

The use of buried dopants to construct quantum-dot cellular automata is investigated as an alternative to conventional electronic devices for information transport and elementary computation. This provides a limit in terms of miniaturisation for this type of system as each potential well is formed by a single dopant atom. As an example, phosphorous donors in silicon are found to have good energy level separation with incoherent switching times of the order of microseconds. However, we also illustrate the possibility of ultra-fast quantum coherent switching via adiabatic evolution. The switching speeds are numerically calculated and found to be 10's of picoseconds or less for a single cell. The effect of decoherence is also simulated in the form of a dephasing process and limits are estimated for operation with finite dephasing. The advantages and limitations of this scheme over the more conventional quantum-dot based scheme are discussed. The use of a buried donor cellular automata system is also discussed as an architecture for testing several aspects of buried donor based quantum computing schemes.

Phosphorus and hydrogen atoms on the (001) surface of silicon: A comparative scanning tunnelling microscopy study of surface species with a single dangling bond

“…This technique has been proposed for building quantum cellular automata [2], single electron transistors [3][4][5], and a Si based quantum computer [6][7][8][9]. In these approaches, STM lithography is used to selectively desorb hydrogen from a hydrogen terminated Si(0 0 1):H surface from the nanometer down to the atomic scale.…”

Conductance modulation by individual acceptors in Si nanoscale field-effect transistors

“…One issue is the establishment of new computer architectures in which charges of individual dopants are used. 1,2 Technologies for the control of the position of single dopants have also been rapidly developing, 3,4 which might lead to a new field, single-dopant electronics, in which we will use the electronic nature of single dopants to manipulate electrons.…”

Measuring decoherence properties of charge qubits using buried donor cellular automata

“…10 The energy difference (E ex −E gs ) between the excited (non-computational) and ground (computational) states of one cell as a function of system size is shown in Fig. 3.…”

“…8,9 Much of the discussion in this paper applies to all QDCA systems, but for concreteness we will concentrate on the case of a buried donor based quantum-dot cellular automata or BDCA. 10 We demonstrate that large variations in measured parameters can be obtained based on the coupling strength and decoherence times, which provides a convenient way to study these parameters. If two dots are placed next to each other, one cell influences the state of the other cell via capacitative coupling.…”