Quantum Dot Cellular Automata

1. Quantum Dot Cellular Automata A Logical Implementation PRESENTED BY : - APOORVA M. BHATT EE5970 COMPUTER ENGINEERING SEMINAR DR. ZHUO FENG

2. 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

3. 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.

4. 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

5. 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

6. 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.

7. NECESSITY OF QUANTUM DOTS: LIMITATIONS OF CURRENT CMOS BASED TECHNOLOGY • CMOS TRANSISTORS CAN NOT BE SCALED BEYOND A PARTICULAR SIZE ANY FURTHER • CMOS INTERCONNECTS HAVE NOT GROWN TO WORK AS FAST AS THE DEVICES THEMSELVES • POWER CONSUMPTION DUE TO LEAKAGE CURRENT IS SIGNIFICANT IN THE CMOS TECHNOLOGY AND HAS NO 100% SOLUTION TO IT AT THIS POINT IN TIME

8. ADVANTAGES OF QUANTUM DOT TECHNOLOGY • OPTIMISTIC ASSUMPTIONS INDICATE THAT THE TECHNOLOGY HAS THE POTENTIAL TO BREAK THE TERAHERTZ BARRIER (THEORETICALLY PROVEN) • POWER CONSUMPTION IS SIGNIFICANTLY LOW AS COMPARED TO THE CMOS TECHNOLOGY • 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

9. 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 • PLANAR QUANTUM DOTS • VERTICAL QUANTUM DOTS • SELF-ASSEMBLED QUANTUM DOTS

10. 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

11. 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.com/experiments/current_projects/Misc.html

12. HOW ARE QUANTUM DOTS GENERATED? • 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

13. HOW ARE QUANTUM DOTS GENERATED? COURTESY : - YOUTUBE VIDEO POSTED BY www.nanophys.ethz.ch

14. 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

15. 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

16. 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)

17. 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)

18. 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)

19. 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

20. 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)

21. 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

22. 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

23. 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

24. 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

25. 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

26. 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

27. 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

28. 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

29. APPLICATIONS OF Quantum dots & QCA • IN QUANTUM COMPUTATION PROCESSING TECHNOLOGY IN ORDER TO OBTAIN HIGHER BANDWIDTH AND OPERATING FREQUENCIES AND FASTER INTERCONNECTS AND LESSER POWER CONSUMPTION • FOR DISPLAY TECHNOLOGY • FOR LASER TECHNOLOGY IN PHOTONICS

30. 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.

31. QUESTIONS / COMMENTS SESSION

32. references • WIKIPEDIA (www.wikipedia.com) • YOUTUBE & THE RESPECTIVE CREATORS FOR THE MULTIMEDIA VIDEOS • 3. ADDER AND MULTIPLIER DESIGN IN QUANTUM DOT CELLULAR AUTOMATA IEEE TRANSACTION JUNE 2009 BYHeumpil Cho, Member, IEEE, and Earl E. Swartzlander, Jr., Fellow, IEEE • 4. QUANTUM CELLULAR AUTOMATA: THEORY AND APPLICATIONS • BY CARLOS A. P´EREZ DELGADO

33. APPRECIATING YOUR PATIENCE FOR THIS INFORMATIVE SESSION