QuantumDot Cellular Automata SPICE Macro Model

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Quantum-Dot Cellular Automata SPICE Macro Model
Electrical and Computer Engr. Department
Rui Tang, Fengming Zhang, Yong-Bin Kim
Electrical and Computer Engineering Department,
Northeastern University

• Why QCA
• CMOS technology has reached physical limits
• Technology Goal
• The cell size of QCA is about
• several nanometers _at_ room temperature
• Alternative Nano technology
• Quantum Cellular Automata (QCA)
• New method of information transformation
• Why SPICE Model
• CAD tools are essential for real application
• QCADesigner is a good bottom-up design
  tool.

QCA Cell and Two-Junction Realization
Majority Voter (MV) FABACBC
device cell

• 4 dots and 2 electrons
• Electrons tend to occupy antipodal dots
• (a) shows two-junction realization of the
  quantum cellular automata
• (b) shows a schematic diagram of the half-QCA
  cell

• AND/OR functions obtained by setting one input of
  MV to
• 0 for AND
• 1 for OR

The Schematic and Function of One-bit QCA
Full-Adder
Graph Representation of QCA SPICE Model
QCA SPICE Model

• The electrostatic energy to move an electron from
  one island i to another island j is given by
• In a simple case, there is only one extra
  electron in one pair of quantum dots.
• Therefore, only two states of the transition
  exist, one state is the extra electron trapped in
  island i and the other state is island j holding
  the extra electron. Therefore, the following
  expression can be obtained
• The tunnel rate is formulated based on the
  orthodox theory and given by
• The changes in energy when an electron tunnels
  from node i to j or an electron tunnels from node
  j to i are
• Once we know the tunnel rate, we can deduce the
  probabilities of the different states in the QCA
  cell

• Cin is the capacitance between the QCA cells
• Ci is the capacitance between the two pairs of
  QCA dots
• RT1 is the junction resistor

Simulation Results
The Traditional CMOS Circuits Design Process and
the Proposed QCA Circuits Design Flow

Truth Table of Full Adder


Conclusions and Future Research
Conclusions
Future Researches

• SPICE model for QCA cell is proposed
• Based on the orthodox theory and single electron
  tunneling
• First effort to develop SPICE macro modeling of
  QCA cells
• Based on experimental demonstrations of QCA cells
• The functions of full-adder and majority voter
  are verified in SPICE

• Develop QCA Synthesis Methodology
• Timing Characterization Across QCA Modules
• Cell Placement/Routing for Room
• Temperature Operation
• Pipeline Design for High Performance