OUTLINE
INTRODUCTION TO QUANTUM DOTS
NECESSITY OF QUANTUM DOTS: LIMITATIONS OF CURRENT CMOS
BASED TECHNOLOGY
HOW ARE QUANTUM DOTS GENERATED?
WHAT IS QUANTUM DOT CELLULAR AUTOMATA (QCA)?
LOGICAL IMPLEMENTATION OF QCA IN QUANTUM COMPUTATION
APPLICATION OF QCA
CONCLUSION
INTRODUCTION TO QUANTUM DOTS
IN ANY MATERIAL, THERE EXISTS A QUASI-PARTICLE NAMED ‘EXCITON’
AN EXICITON IS DEFINED AS THE BOUND STATE OF AN ELECTRON AND HOLE
WHICH ARE ATTRACTED TO EACH OTHER BY COULOMB’S ELECTROSTATIC
FORCE
------------- WIKIPEDIA
A QUANTUM DOT IS A SEMICONDUCTOR WHOSE EXCITONS ARE CONFINED
IN ALL THREE SPATIAL DIMENSIONS. AS A RESULT, THEY HAVE PROPERTIES
THAT ARE BETWEEN THOSE OF BULK SEMICONDUCTORS AND THOSE OF
DISCRETE MOLECULES.
QUANTUM DOTS, THUS, ARE SEMICONDUCTOR NANOCRYSTALS OF RANGE
2-10 nm (10 – 50 ATOMS) IN DIAMETER AND SINCE THEY ARE SO SMALL,
THEY ARE CONSIDERED DIMENSIONLESS.
SIMULATED QUANTUM DOT GENERATION
SOURCE: - http://www.onlineinvestingai.com/blog/2009/02/04/whats-the-spin-on-quantum-dots/
National Institute of Nanotechnology at the University of Alberta
UNDERSTANDING QUANTUM DOTS
IN ITS TRUE FORM, QUANTUM DOTS CAN BE UNDERSTOOD TO BE SMALL
DEVICES CONTAINING TINY DROPLET OF FREE ELECTRONS.
THUS, ANY QUANTUM DOT CONSISTS OF ANYTHING FROM A SINGLE
ELECTRON TO A CLUSTER OF A NUMBER OF ELECTRONS.
IT CAN BE UNDERSTOOD TO BE AN ARTIFICALLY CREATED ATOM WITH 3D
SPATIAL CONFINEMENT OF ELECTRONS WITH THE ONLY DIFFERENCE BEING
THAT THERE CAN BE SIGNIFICANT CHANGE IN THE PROPERTIES OF THE
QUANTUM DOT EVEN IF A SINGLE ELECTRON WERE TO LEAVE THE
STRUCTURE.
ANIMATION
----------- WIKIPEDIA
AN EXAMPLE OF QUANTUM DOTS
COURTESY:- The size of the quantum
dots can be tuned to produce several
different colors (Image: Nature)
COURTESY:- The structural aspects and light-emitting
properties of quantum dots P. O’Brien, S. S. Cummins, D. Darcy, A.
Dearden, O. Masala, N. L. Pickett, S. Ryley and A. J. Sutherland (2003),
“Quantum dot-labelled polymer beads by suspension polymerization.”
Chem. Commun. 2532-2533 and www.nanoco.biz.
NECESSITY OF QUANTUM DOTS: LIMITATIONS OF
CURRENT CMOS BASED TECHNOLOGY
1. CMOS TRANSISTORS CAN NOT BE SCALED BEYOND A
PARTICULAR SIZE ANY FURTHER
2. CMOS INTERCONNECTS HAVE NOT GROWN TO WORK
AS FAST AS THE DEVICES THEMSELVES
3. POWER CONSUMPTION DUE TO LEAKAGE CURRENT IS
SIGNIFICANT IN THE CMOS TECHNOLOGY AND HAS NO
100% SOLUTION TO IT AT THIS POINT IN TIME
ADVANTAGES OF QUANTUM DOT TECHNOLOGY
1. OPTIMISTIC ASSUMPTIONS INDICATE THAT THE TECHNOLOGY HAS THE
POTENTIAL TO BREAK THE TERAHERTZ BARRIER (THEORETICALLY PROVEN)
2. POWER CONSUMPTION IS SIGNIFICANTLY LOW AS COMPARED TO THE
CMOS TECHNOLOGY
3. THE INTERCONNECTS DESIGNED WITH QCA WOULD BE FASTER AND
WOULD WORK ALMOST UP TO THE SPEED OF THE PROCESSING DEVICE
WHICH WOULD DRASTICALLY ENHANCE THE SYSTEM PERFORMANCE
Courtesy:- Quantum-dot Cellular Automata (QCA) - Logic Gates
By John C. Bean University of Virginia, Charlottesville, VA
HOW ARE QUANTUM DOTS GENERATED?
ESSENTIALLY QUANTUM DOTS ARE OF 3 TYPES DEPENDING ON THE
PHYSICS OF HOW THE ELECTRON CONFINEMENT OCCURS IN THE
SEMICONDUCTOR MATERIAL
1. PLANAR QUANTUM DOTS
2. VERTICAL QUANTUM DOTS
3. SELF-ASSEMBLED QUANTUM DOTS
HOW ARE QUANTUM DOTS GENERATED?
QUANTUM DOTS ARE GENERATED BY THE PHENOMENON KNOWN AS
ELECTRON TRAPPING OR CONFINEMENT IN AN ENERGY WELL OF DISCRETE
MAGNITUDE. THIS WOULD GENERATE ‘EXCITONS’ IN AN ATOM
THERE ARE DIFFERENT WAYS OF CONFINING THE EXCITONS AND HENCE
THERE ARE DIFFERENT WAYS TO GENERATE THE QUANTUM DOTS.
COLLOIDAL
QUANTUM
DOTS IRRADIATED WITH A
UV LIGHT. DIFFERENT SIZED
QUANTUM DOTS EMIT
DIFFERENT COLOR LIGHT
DUE
TO
QUANTUM
CONFINEMENT.
Courtesy:- WIKIPEDIA – QUANTUM DOTS
HOW ARE QUANTUM DOTS GENERATED?
•
COLLOIDAL SEMICONDUCTOR NANOCRYSTALS IRRADIATED WITH ULTRAVIOLET
LIGHT. QUANTUM CONFINEMENT CAUSES THE BAND GAP ENERGY TO VARY WITH
THE NANOCRYSTAL'S SIZE. EACH VIAL CONTAINS A MONODISPERSE SAMPLE OF
NANOCRYSTALS DISPERSED IN A LIQUID SOLVENT (FIGURE IN THE PREVIOUS SLIDE)
•
FOLLOWING ARE THE MOST COMMON WAYS OF PRODUCING THE QUANTUM DOTS
1. COLLOIDAL SYNTHESIS : - INVOLVES BINARY ALLOYS SUCH AS CADMIUM
SELENIDE, CADMIUM SULFIDE, INDIUM ARSENIDE,
AND INDIUM PHOSPHIDE. ALTHOUGH, DOTS MAY ALSO BE
MADE FROM TERNARY ALLOYS SUCH AS CADMIUM
SELENIDE SULFIDE.
Courtesy:- AMAZING RUST
http://www.amazingrust.c
om/experiments/current_
projects/Misc.html
HOW ARE QUANTUM DOTS GENERATED?
2.
FABRICATION:QUANTUM
DOTS
DEFINED
BY LITHOGRAPHICALLY PATTERNED GATE ELECTRODES, OR BY
ETCHING ON TWO-DIMENSIONAL ELECTRON GASES IN
SEMICONDUCTOR HETEROSTRUCTURES CAN HAVE LATERAL
DIMENSIONS EXCEEDING 100 NM
COURTESY:- QUANTUM DOTS BY ULTRAVIOLET AND X-RAY
LITHOGRAPHY BY MASSIMO F BERTINO1,7
HOW ARE QUANTUM DOTS GENERATED?
COURTESY : - YOUTUBE VIDEO POSTED BY www.nanophys.ethz.ch
HOW ARE QUANTUM DOTS GENERATED?
3. OTHER FABRICATION TECHNIQUES INCLUDE VIRAL ASSEMBLY
(BIOLOGICALLY PRODUCED USING VIRUS DNA), ELECTROCHEMICAL
ASSEMBLY, BULK MANUFACTURE (USES A PROCESS CALLED “HIGH
TEMPERATURE DUAL INJECTION” WHICH IS IMPRACTICAL FOR
MOST COMMERCIAL APPLICATIONS THAT REQUIRE LARGE
QUANTITIES OF QUANTUM DOTS) & CADMIUM FREE QDs (FREE
FROM CdSe SINCE CADMIUM IS A HEAVY METAL AND USES RARE
EARTH METALS)
------------- WIKIPEDIA
WHAT IS QUANTUM DOT CELLULAR AUTOMATA
(QCA) ? - INTRODUCTION
COURTESY : - YOUTUBE VIDEO POSTED BY UNIVERSITY OF ALBERTA, CA
http://www.phys.ualberta.ca/~wolkow/news.php
WHAT IS QUANTUM DOT CELLULAR AUTOMATA
(QCA) ? – QUANTUM CELL DEFINED
1) SHOWS A SIMPLIFIED DIAGRAM OF A QUANTUM-DOT CELL. IF THE CELL IS CHARGED WITH
TWO ELECTRONS, EACH FREE TO TUNNEL TO ANY SITE IN THE CELL, THESE ELECTRONS WILL TRY TO
OCCUPY THE FURTHEST POSSIBLE SITE WITH RESPECT TO EACH OTHER DUE TO MUTUALELECTROSTATIC
REPULSION. THEREFORE, TWO DISTINGUISHABLE CELL STATES EXIST. 2) SHOWS THE TWO POSSIBLE
MINIMUM ENERGY STATES OF A QUANTUM-DOT CELL. THE STATE OF A QCA REPRESENTS
ITS POLARIZATION, DENOTED AS P. ALTHOUGH ARBITRARY IN MEANING, USING CELL POLARIZATION P = -1
TO REPRESENT LOGIC “0” AND P = +1 TO REPRESENT LOGIC “1” HAS BECOME STANDARD PRACTICE. 3) A
WIRE OF QD CELLS.
COURTESY:- WIKIPEDIA (QUANTUM DOT CELLULAR AUTOMATON)
WHAT IS QUANTUM DOT CELLULAR AUTOMATA
(QCA) ? – LOGIC DESIGN
•
ASSUMING INPUTS A AND B EXIST IN A
“BINARY 0” STATE AND INPUT C EXISTS IN A
“BINARY 1” STATE, THE OUTPUT WILL EXIST IN
A
“BINARY
0”
STATE
AS
THE
CONJUNCT ELECTRICAL FIELD EFFECT OF
INPUTS A AND B IS GREATER THAN THE ONE
OF INPUT C. IN OTHER WORDS, THE MAJORITY
GATE DRIVES THE OUTPUT CELL’S STATE TO BE
EQUAL TO THAT OF THE MAJORITY OF THE
INPUTS. NOW, IF THE POLARIZATION OF INPUT
C WERE TO BE FIXED TO SAY, BINARY 0, THE
ONLY WAY THE OUTPUT’S STATE BECOMES
BINARY 1, IS IF INPUT A AND B ARE ALSO 1.
OTHERWISE, THE OUTPUT CELL WILL EXHIBIT
A BINARY 0 STATE.
COURTESY:- WIKIPEDIA (QUANTUM DOT CELLULAR AUTOMATON)
WHAT IS QUANTUM DOT CELLULAR AUTOMATA
(QCA) ? – LOGIC DESIGN
THE OUTPUT CELL
SERIES HAS TO BE AT
450 FROM THE TWO
LOGICALLY
LIKE
INPUTS TO REALIZE A
‘NOT’ OR INVERTER
LOGIC
COURTESY:- WIKIPEDIA (QUANTUM DOT CELLULAR AUTOMATON)
CELL STATE TRANSITION FOR LOGIC DEFINITION
• QCA CELLS CAN ONLY BE FOUND IN TWO STATES (LOGIC ‘0’ AND ‘1’)
•
THE SITUATIONAL CHANGE IN THE STATE OF THE CELL UNDERGOING
TRANSITION IS RELATIONAL IN NATURE AND HIGHLY DEPENDS ON THE STATE OF
ITS ADJACENT NEIGHBORS
•
THE MOST IMPORTANT ROLE TO GENERATE THE LOGIC USING QCA IS TO
DEFINE METHOD TO CONTROL DATA FLOW WHICH IS INTURN NECESSARY TO
DEFINE THE DIRECTION IN WHICH STATE TRANSITION OCCURS IN QCA CELLS
CELL STATE TRANSITION FOR LOGIC DEFINITION
THE QCA CLOCK, ITS STAGES
AND ITS EFFECTS ON A CELL’S
ENERGY BARRIERS
A
TYPICAL
QCA
DESIGN
REQUIRES FOUR CLOCKS, EACH
OF WHICH IS CYCLICALLY 90
DEGREES OUT OF PHASE WITH
THE PRIOR CLOCK
COURTESY:- WIKIPEDIA (QUANTUM DOT CELLULAR AUTOMATON)
ADDER DESIGN IN QCA
- CARRY FLOW ADDERS
•
IN THE QCA TECHNOLOGY, THE PROPAGATION DELAY AND COMPLEXITY
INCREASES WITH THE INCREASE IN THE NUMBER OF CELLS APPLIED TO
RESOLVE A LOGIC
•
THE IDEA IS TO USE AS FEWER CELLS AS POSSIBLE TO REALIZE THE GIVEN
LOGIC AND AVOIDING THE ADDITION OF ADDITIONAL PROPAGATION
DELAY AND COMPLEXITY.
EQUATIONS FOR SUM AND CARRY FOR CARRY FLOW ADDER ARE
Si = aibici + a’ib’icI + a’i bi c’i + a’i bi ci
ci+1 = aibi + bici +aici
ADDER DESIGN IN QCA
- CARRY FLOW ADDERS
FULL ADDER FOR THE
CARRY FLOW ADDER.
(A) SCHEMATIC. (B)
LAYOUT.
COURTESY : - ADDER AND MULTIPLIER DESIGN IN QUANTUM-DOT CELLULAR
AUTOMATA HEUMPIL CHO, MEMBER, IEEE, AND EARL E. SWARTZLANDER, JR.,
FELLOW, IEEE
ADDER DESIGN IN QCA
- CARRY FLOW ADDERS
SIMULATION RESULTS
FOR 8-BIT CFA.
The first meaningful
output appears in the
third clock period after
2(2/4) clock delays.
First
and
last
input/output pairs are
highlighted.
COURTESY : - ADDER AND MULTIPLIER DESIGN IN QUANTUM-DOT CELLULAR
AUTOMATA HEUMPIL CHO, MEMBER, IEEE, AND EARL E. SWARTZLANDER, JR.,
FELLOW, IEEE
ADDER DESIGN IN QCA
- CARRY FLOW ADDERS
FULL ADDER FOR THE
CARRY FLOW ADDER.
(A) SCHEMATIC. (B)
LAYOUT.
COURTESY : - ADDER AND MULTIPLIER DESIGN IN QUANTUM-DOT CELLULAR
AUTOMATA HEUMPIL CHO, MEMBER, IEEE, AND EARL E. SWARTZLANDER, JR.,
FELLOW, IEEE
ADDER DESIGN IN QCA
- CARRY LOOK-AHEAD ADDERS
•
IN A SIMILAR FASHION, WE CAN DESIGN A CARRY LOOKAHEAD ADDER
WHICH BASICALLY ONLY ADDS THE CARRY
ROUGLY TWICE
AS BIG AS THE
CARRY FLOW
ADDER
IN
TERMS
OF
WIDTH
AND
LENGTH
COURTESY : - ADDER AND MULTIPLIER DESIGN IN QUANTUM-DOT CELLULAR
AUTOMATA HEUMPIL CHO, MEMBER, IEEE, AND EARL E. SWARTZLANDER, JR.,
FELLOW, IEEE
COMPARISON OF CLA AND CFA FOR VARIOUS
OPERAND SIZES
COURTESY : - ADDER AND MULTIPLIER DESIGN IN QUANTUM-DOT CELLULAR
AUTOMATA HEUMPIL CHO, MEMBER, IEEE, AND EARL E. SWARTZLANDER, JR.,
FELLOW, IEEE
MULTIPLICATION DESIGN USING QCA
COURTESY : - ADDER AND MULTIPLIER DESIGN IN QUANTUM-DOT CELLULAR
AUTOMATA HEUMPIL CHO, MEMBER, IEEE, AND EARL E. SWARTZLANDER, JR.,
FELLOW, IEEE
SIMULATION RESULT OF MULTIPLIER QCA
COURTESY : - ADDER AND MULTIPLIER DESIGN IN QUANTUM-DOT CELLULAR
AUTOMATA HEUMPIL CHO, MEMBER, IEEE, AND EARL E. SWARTZLANDER, JR.,
FELLOW, IEEE
APPLICATIONS OF QUANTUM DOTS & QCA
1.
IN
QUANTUM
COMPUTATION
PROCESSING
TECHNOLOGY IN ORDER TO OBTAIN HIGHER
BANDWIDTH AND OPERATING FREQUENCIES AND
FASTER INTERCONNECTS AND LESSER POWER
CONSUMPTION
2.
FOR DISPLAY TECHNOLOGY
3.
FOR LASER TECHNOLOGY IN PHOTONICS
CONCLUSION
•
QUANTUM CELLULAR AUTOMATA IS CURRENTLY VIEWED AS THE MOST
SUITABLE SUCCESSOR TO THE ILLUSTRIOUS CMOS VLSI SYSTEM
PREVALENT TODAY DUE TO ITS ADVANTAGES MENTIONED.
•
QUANTUM CELLULAR AUTOMATA TECHNOLOGY WOULD BE USED IN THE
FUTURE FOR DEVELOPING A HIGH SPEED PROCESSORS AND ASICs THAT
WOULD BE USED FOR BOTH GENERAL PURPOSE AND TASK-SPECIFIC
COMPUTING REQUIREMENTS
•
QCA HAS EMERGED TO BE THE PROBLEM SOLVER IN THE TIMES WHEN
THE WORLD IS LOOKING AT A BOTTLE-NECK OF SCALABILITY IN CMOS
INDUSTRY.
REFERENCES
1. WIKIPEDIA
(www.wikipedia.com)
2. YOUTUBE & THE RESPECTIVE CREATORS FOR THE MULTIMEDIA VIDEOS
3. ADDER AND MULTIPLIER DESIGN IN QUANTUM DOT CELLULAR
AUTOMATA IEEE TRANSACTION JUNE 2009 BY Heumpil Cho, Member,
IEEE, and Earl E. Swartzlander, Jr., Fellow, IEEE
4. QUANTUM CELLULAR AUTOMATA: THEORY AND APPLICATIONS
BY CARLOS A. P´EREZ DELGADO
APPRECIATING YOUR
INFORMATIVE SESSION
PATIENCE
FOR
THIS