Quantum Cellular Automata : Theory, Experimentation and Prospects

by Macucci, Massimo

• ISBN13: 9781860946325
• ISBN10: 1860946321
• Format: Hardcover
• Copyright: 2006-07-01
• Publisher: World Scientific Pub Co Inc

Summary

The Quantum Cellular Automaton (QCA) concept represents an attempt to break away from the traditional three-terminal device paradigm that has dominated digital computation. Since its early formulation in 1993 at Notre Dame University, the QCA idea has received significant attention and several physical implementations have been proposed. This book provides a comprehensive discussion of the simulation approaches and the experimental work that have been undertaken on the fabrication of devices capable of demonstrating the fundamentals of QCA action. Complementary views of future perspectives for QCA technology are presented, highlighting a process of realistic simulation and of targeted experiments that can be assumed as a model for the evaluation of future device proposals. Contents: The Concept of Quantum-Dot Cellular Automata (C S Lent); Simulation with the Occupation-Number Hamiltonian (M Macucci & M Governale); Realistic Time-Independent Models of a QCA Cell (J Martorell et al.); Time-Independent Simulation of QCA Circuits (L Bonci et al.); Simulation of the Time-Dependent Behavior of QCA Circuits with the Occupation-Number Hamiltonian (I Yakimenko & K-F Berggren); Time-Dependent Analysis of QCA Circuits with the Monte Carlo Method (L Bonci et al.); Implementation of QCA Cells with SOI Technology (F E Prins et al.); Implementation of QCA Cells in GaAs Technology (Y Jin et al.); Non-Invasive Charge Detectors (G Iannaccone et al.); Metal Dot QCA (G L Snider et al.); Molecular QCA (C S Lent); Magnetic Quantum-Dot Cellular Automata (MQCA) (A Imre et al.). Readership: Physicists, electronic engineers and academics.

Table of Contents

Preface
1 The Concept of Quantum-Dot Cellular Automata	1	(16)
C.S. Lent
1.1 Needed: A New Device Paradigm for the Nanoscale	1	(1)
1.2 The Physical Representation of Information	2	(1)
1.3 Dots in QCA	3	(1)
1.3.1 Metal dots	3	(1)
1.3.2 Molecular dots	4	(1)
1.3.3 Semiconductor dots	4	(1)
1.4 QCA Cells	4	(1)
1.5 The Quantum-Dot Cellular Automata Paradigm	5	(2)
1.6 Clocked QCA Cells	7	(1)
1.7 Clocked QCA Shift Devices	8	(1)
1.8 Power Gain	8	(1)
1.9 Robustness against Thermal Errors and Defects	9	(4)
1.10 Conclusions	13	(1)
References	14	(3)
2 QCA Simulation with the Occupation-Number Hamiltonian	17	(8)
M. Macucci and M. Governale
2.1 Introduction	17	(1)
2.2 Formulation of the Occupation-Number Hamiltonian	18	(1)
2.3 Diagonalization of the Occupation-Number Hamiltonian	19	(1)
2.4 Application to the Evaluation of the Effects of Geometric Asymmetry on the Cell-to-Cell Response Function	20	(3)
References	23	(2)
3 Realistic Time-Independent Models of a QCA Cell	25	(40)
J. Martorell, D.W.L. Sprung, M. Girlanda, and M. Macucci
3.1 Introduction	25	(1)
3.2 Heterostructure with a Uniform Gate	26	(1)
3.3 Linear Gate	27	(6)
3.4 Linear Gate Deposited on Etched Surface	33	(3)
3.5 Modeling of a Complete QCA Cell	36	(1)
3.6 The Configuration-Interaction Method	37	(9)
3.6.1 Cell defined with a hole-array gate	41	(3)
3.6.2 Multiple-gate cell	44	(2)
3.7 Analysis of Cells with more than 2 Electrons	46	(6)
3.7.1 Many-electron driver cell	47	(2)
3.7.2 Semiclassical model	49	(1)
3.7.3 Many-electron driver cell	50	(2)
3.8 Analysis of Polarization Propagation along a Semiconductor-Based Quantum Cellular Automaton Chain	52	(5)
3.8.1 Model of a three-cell chain	52	(5)
3.9 Results	57	(5)
References	62	(3)
4 Time-Independent Simulation of QCA Circuits	65	(22)
L. Bonci, S. Frunraviglia. M. Gattabigio, C. Ungarelli, G. Iannaccone, and M. Macucci
4.1 Introduction	65	(2)
4.2 Semiclassical Alodel of QCA Circuits	67	(6)
4.3 Thermal Behavior	73	(4)
4.4 Analytical Model	77	(7)
4.4.1 Numerical simulation of more complex circuits	80	(4)
References	84	(3)
5 Simulation of the Time-Dependent Behavior of QCA Circuits with the Occupation-Number Hamiltonian	87	(22)
I. Yakimenko and K.-F. Berggren
5.1 Introduction	87	(1)
5.2 Modeling of Chains of Quantum Cells	87	(2)
5.3 Time Evolution of Polarization for a Chain of QCA Cells without Dissipation	89	(4)
5.4 Time Evolution of Polarization for a Chain of QCA Cells with Dissipation	93	(4)
5.5 Imperfections: Variable Coupling Strength, Defects, Stray Charges	97	(10)
5.5.1 Variations of the intercellular distances	99	(5)
5.5.2 Defects in interdot barriers	104	(2)
5.5.3 Effect of stray charges	106	(1)
References	107	(2)
6 Time-Dependent Analysis of QCA Circuits with the Monte Carlo Method	109	(34)
L. Bonci, M. Gattobigio, G. Iannaccone, and M. Macucci
6.1 Introduction	109	(1)
6.2 Six-Dot QCA Cell	110	(6)
6.2.1 Transition rates for a semi-cell	113	(3)
6.3 Analysis of the Parameter Space	116	(8)
6.3.1 Tunneling rate	116	(4)
6.3.2 Calculation of the energy imbalance	120	(4)
6.4 Simulation of Clocked and Nonclocked Devices	124	(15)
6.4.1 QCA circuit simulator	125	(1)
6.4.2 Simulation strategy	126	(2)
6.4.3 Binary wire simulations	128	(9)
6.4.4 Operation of a logic gate	137	(2)
6.5 Discussion	139	(1)
References	140	(3)
7 Implementation of QCA Cells with SOI Technology	143	(36)
F.E. Prins, C. Single, G. Wetekara, D.P. Kern, M. Macucci, L. Bonci, G. Iannaccone, and M. Gattobigio
7.1 Advantages of the SOI Material System	143	(5)
7.2 Fabrication of Si-Nanostructures	148	(1)
7.3 Experiments with the SOI Material System	148	(6)
7.4 Electrical Characterization of Double Dots	154	(3)
7.5 Electrical Characterization of a 4 Dot QCA Cell	157	(6)
7.6 Concept of an Experiment for the Detection of QCA Operation	163	(10)
7.7 Simulations	173	(2)
7.8 Possible Improvements	175	(1)
References	176	(3)
8 Implementation of QCA Cells in GaAs Technology	179	(34)
Y. Jin, C.G. Smith, J. Martorell, D.W.L. Sprung, P.A. Machado, M. Girlanda, M. Governale, G. Iannaccone, and M. Macucci
8.1 Introduction	180	(1)
8.2 Nanofabrication of GaAs Devices	180	(5)
8.3 Evaluation of the Achievable Precision	185	(4)
8.4 Electrical Characterization of QPCs	189	(1)
8.5 Modeling of Quantum Point Contacts: The Issue of Boundary Conditions	189	(5)
8.6 Electron Decay from an Isolated Quantum Dot	194	(17)
8.6.1 Lifetimes of the experimentally studied dot	194	(2)
8.6.2 Statistical analysis of the experimental data	196	(1)
8.6.3 First decays	197	(1)
8.6.4 Later decays	197	(1)
8.6.5 Modeling of electron decay from the isolated quantum dot	198	(2)
8.6.6 Theoretical framework	200	(1)
8.6.7 Equilibrium dot	201	(1)
8.6.8 Dot with excess electrons	201	(4)
8.6.9 Quasibound states of the dot	205	(3)
8.6.10 Results and discussieu	208	(3)
References	211	(2)
9 Non-Invasive Charge Detectors	213	(16)
G. Iannaccone, C. Ungarelli, M. Governale, M. Macucci, S. Gardelis, C.G. Smith, J. Cooper, D.A. Ritchie, and E.H. Linfield
9.1 Introduction	213	(1)
9.2 Experiments on a Double Dot System with Non-Invasive Detector	214	(2)
9.3 Numerical Simulation of the Dot-Detector System	216	(8)
9.4 Determining the Operation of a AlGaAs-GaAs QCA Cell	224	(3)
9.5 Conclusion	227	(1)
References	227	(2)
10 Metal Dot QCA	229	(26)
G.L. Snider, A.O. Orlov, and R.K. Kummamuru
10.1 Introduction	229	(1)
10.2 QCA Cell	229	(2)
10.3 Clocked QCA Devices Fabricated Using Metal Tunnel Junctions	231	(1)
10.4 Charging Process in QCA Half-Cell	231	(8)
10.5 QCA Latch Operation	239	(8)
10.6 Two Stage QCA Shift Register a Clocked QCA Cell	247	(1)
10.7 Simulation of a Multi-Stage Shift Register	248	(1)
10.8 QCA Power Gain	249	(4)
References	253	(2)
11 Molecular QCA	255	(14)
C.S. Lent
11.1 Introduction	255	(1)
11.2 Aviram's Molecule: A Simple Model System	256	(5)
11.3 A Functioning Two-Dot Molecular QCA Cell	261	(3)
11.4 A Four-Dot Molecular QCA Cell	264	(1)
11.5 Conclusions	264	(2)
References	266	(3)
12 Magnetic Quantum-Dot Cellular Automata (MQCA)	269	(8)
A. Imre, G. Csaba, G.H. Bernstein, and W. Porod
12.1 Introduction	269	(2)
12.2 Magnetic QCA Structures	271	(2)
12.3 Modeling of Magnetic QCA Arrays	273	(2)
12.4 Conclusion	275	(1)
References	275	(2)
13 Final Remarks and Future Perspectives	277	(4)
M. Marucci
Index	281