Showing papers by "Craig S. Lent published in 1998"

Demonstration of a six-dot quantum cellular automata system

Abstract: We report an experimental demonstration of a logic cell for quantum-dot cellular automata (QCA). This nanostructure-based computational paradigm allows logic function implementation without the use of transistors. The four-dot QCA cell is defined by a pair of series-connected double dots, and the coupling between the input and the output double dots is provided by lithographically defined capacitors. We demonstrate that, at low temperature, an electron switch in the input double dot induces an opposite electron switch in the output double dot, resulting in a polarization change of the QCA cell. Switching is verified from the electrometer signals, which are coupled to the output double dot. We perform theoretical simulations of the device characteristics and find excellent agreement with theory.

Demonstration of a functional quantum-dot cellular automata cell

Abstract: We report an experimental demonstration of a functional cell for quantum-dot cellular automata (QCA), a transistorless approach to implement logic functions. The four-dot QCA cell is defined by a pair of series-connected, capacitively coupled input and output double dots. We demonstrate that, at low temperature, an electron switch in the input double dot induces an opposite electron switch in the output double dot, resulting in a complete polarization change of the QCA cell. Switching is verified by electrometer signals which are coupled to the output double dot. Experimental results suggest that electron motion in the coupled double dots is strongly correlated and can support high operating frequencies. Agreement between theoretical predictions and experimentally measured values of the dot potentials is excellent.

Experimental demonstration of quantum-dot cellular automata

Abstract: We present the experimental demonstration of a basic cell of quantum-dot cellular automata (QCA), a transistorless computation paradigm which addresses the issues of device density and interconnection. The device presented is a six-dot quantum-dot cellular system consisting of a four-dot QCA cell and two electrometer dots. The system is fabricated using metal dots which are connected by capacitors and tunnel junctions. The operation of a basic cell is confirmed by the externally controlled polarization change of the cell. The cell exhibits a bistable response, with more than 80% polarization of the charge within a cell.

A functional cell for quantum-dot cellular automata

Abstract: We present experimental demonstration of a basic cell of Quantum-dot Cellular Automata, a transistorless computation paradigm which addresses the issues of device density and interconnection. The devices presented consist of four and six-dot quantum-dot cellular systems where the metal dots are connected by capacitors and tunnel junctions. The operation of a basic cell is confirmed by the externally controlled polarization change of the cell. The cell exhibits a bistable response and voltage gain. We present an experimental technique which cancels the parasitic cross-talk capacitors in the system.

Correlated electron transport in coupled metal double dots

Abstract: The electrostatic interaction between two capacitively coupled, series-connected metal double dots is studied at low temperatures. Experiment shows that when the Coulomb blockade is lifted, by applying appropriate gate biases, in both double dots simultaneously, the conductance through each double dot becomes significantly lower than when only one double dot is conducting a current. The conductance lowering seen in interacting double dots is compared to that caused by an external ac modulation applied to the double-dot gates. The results suggest that the conductance lowering in each double dot is caused by a single-electron tunneling in the other double dot. Here, each double dot responds to the instantaneous, rather than average, potentials on the other double dot. This leads to correlated electron motion within the system, where the position of single electron in one double dot controls the tunneling rate through the other double dot.

Quantum computing with quantum-dot cellular automata using coherence vector formalism

Abstract: A coherence vector formalism is used to describe quantum computing with quantum-dot cellular automata, and the realizations of basic quantum gates are also discussed.

Quantum-Dot Cellular Automata - Experimental Demonstration of a Functional Cell

Abstract: : The experimental demonstration of a basic cell of Quantum Dot Cellular Automata, a transistorless conmutation paradigm is presented The device studied is a six-dot quantum dot cellular system consisting of a four-dot QCA cell and two electrometer dots The system is fabricated using metal dots, connected by capacitors and tunnel junctions The operation of a basic cell is confirmed by the externally detected change of the cell polarization controlled by the input signal The cell exhibits a bistable response, with more than 80% charge polarization within a cell