minimum cost fault tolerant adder circuits in reversible logic synthesis

Minimum Cost Fault Tolerant Adder Circuits in Reversible Logic

Synthesis

Sajib Kumar Mitra*

Department of Computer Science and EngineeringFaculty of Engineering and Technology

University of Dhaka, Dhaka-1000, BangladeshE-mails: sajibmitra.csedu@yahoo.com, farhan717@cse.univdhaka.edu

*Corresponding Author and Presenter

Purposes

• Minimization of Quantum Cost

• Fault Tolerant Circuit

• Reduction of Critical Path Delay

• Reduction of Number of Gates

• Garbage Outputs Optimization

Overview

• Reversible and Quantum Computing

• Quantum Realization of Reversible Circuits

• Fault Tolerant Mechanism

• Proposed Designs of Adder Circuits

• Performance Analysis

• Conclusion

Reversible and Quantum Computing

Reversible Computing

• Equal number of input states and output states• Preserves an unique mapping between input and

output vectors for any Reversible circuit• One or more operations can be united called

Reversible Gate• (N x N) Reversible Gate has N number of inputs and

N number of outputs where N= {1, 2, 3, …}

[1] A. K. Biswas, M. M. Hasan, A. R. Chowdhury, and H. M. H. Babu, “Efficient approaches for designing reversible binary coded decimalimplement in a single adders,” Microelectronics Jounrnal, vol. 39, no. 12, pp. 1693–1703, December 2008.

A

BA B

3

2

1

0

1

0

INP

UT

VE

CT

OR

(A

, B)

OU

TP

UT

VE

CT

OR

(A

B

)

OU

TP

UT

VE

CT

OR

(P

, Q)

3

2

1

0

2

1

INP

UT

VE

CT

OR

(A

, B)

FGA

B Q=A B

P=A

0

3

(a) Irreversible EX-OR operation (b) Reversible EX-OR operation

• Limitation • Feedback is strictly restricted • Fan-out must be one always

Fig. 1: Basic difference between Irreversible and Reversible Circuits

Reversible Computing…

F2GA

BC

A

A C

A B

(d) Feynman Double Gate

PGA

BC

AA B

AB C

(b) Peres Gate

FRGA

BC

A

A’C AB

A’B AC

(f) Fredkin Gate

TGA

BC

A

AB C

B

(c) Toffoli Gate

NFTA

BC

AC’ B’CAC’ BC

A B

(e) New Fault Tolerant Gate

FGAA

B A B

(a) Feynman Gate

Fig. 2: Popular Reversible gates

Reversible Computing…

In Quantum Computing, encode information as a series of quantum-mechanical states such as spin directions of electrons or polarization orientations of a photon that might represent as or might represent a superposition of the two values.

Encoded data is represented by qubits rather than bits which can perform certain calculations exponentially faster than conventional computing.

10 q

Quantum Computing

[2]W. N. N. Hung, X. Song, G. Yang, J. Yang, and M. Perkowski, “Quantum logic synthesis by symbolic reachability analysis,” in 41st Conference on (DAC’04), Design Automation Conference, May 2004, pp. 838–841.

Quantum Computation uses matrix multiplication rather than conventional Boolean operations and the information measurement is realized by calculation the state of qubits .

The matrix operations over qubits are simply specifies by using quantum primitives. For example,

›|B A

|A

|B

|A

›(a) Quantum XOR operation (b) Equivalent matrix

for XOR

UCN=

1 0 0 00 1 0 00 0 0 10 0 1 0

››

Fig. 3: Reversible behavior of Quantum matrix operation

Quantum Computing…

Q= |B A

››

|A

|B ›Quantum XOR operation

›P= |AInput Output

A B P Q

0 0 0 0

0 1 0 1

1 0 1 1

1 1 1 0

Input/output

PatternSymbol

00 a

01 b

10 c

11 d

Quantum Computing…

Fig. 4: Working Principle of Unitary Controlled NOT (UCN)

1 0 0 00 1 0 00 0 0 10 0 1 0

abcd

abdc

Quantum Realization of Reversible Circuits

Quantum Cost

• Quantum Cost (QC): Total number of 2x2 quantum primitives (4x4 unitary matrices) which are used to form equivalent quantum circuit of any Reversible Circuit.

A A

B VIF (A ) THEN V(B )

ELSE B

A A

B V+ IF (A ) THEN V+(B ) ELSE B

A A

B A B

(b) EXclusive-OR

A A’

(a) NOT, Cost =0

(c) Square Root of NOT (d) Hermitian of SRN

Fig. 5: Several Quantum Primitives[3] M. Perkowski and et al, “A hierarchical approach to computer-aided design of quantum circuits,” in 6th International Symposium on Rep-resentations and Methodology of Future Computing Technology, 2003, pp. 201–209.

A A

B B

V V+

A

B

A

B

V V

A

B

A

B

T(a)

T(b)

The attachment of SRN (Hermitian Matrix of SRN) and EX-OR gate on the

same line generates symmetric gate pattern has a cost of 1.

Here T= V or V+

Fig. 6: Difference interactions between Quantum Primitives

Orientation of Quantum Gates

F2G, Cost = 2

A

A B

A

B

C A C

TG, Cost = 5

VV V+

B

AA

B

C AB C

Fig. 7: Equivalent Quantum Circuits of Reversible Gates

Quantum Cost of Reversible gates

FRG, Cost = 5

V

A

BC

A

V V+

A’B AC

A’C AB

VV V+

A B

AA

B

C AB C

PG, Cost = 4

DMIG, Cost = 7

ABC

Peres Gate

A

AB CAB’ D

A B

TG, Cost = 5

VV V+

Q= B

P= AA

B

C R= AB C

TGAB

C

P=A

R=AB C

Q=B

Working Principle of Quantum Circuit

How does Quantum

circuit work?

Fig. 8: Toffoli Gate and corresponding Quantum Circuit

V

1

1

C V R=C’

INPUT OUTPUT

A B R

0 0 C

0 1 C

1 0 C

1 1 C’

V

0

1

C V R=CV+ V

1

0

C V R=CV+

Fig. 9: Working Principle of Quantum Equivalent of TG

Working Principle of Quantum Circuit…

Working Principle of Quantum Circuit…

TGAB

C

P=A

R=AB C

Q=B

V

A

B

C V V+ R=AB C

A

B

INPUT OUTPUT

A B R

0 0 C

0 1 C

1 0 C

1 1 C’

V

A

B

C V V+ R=AB C

P=A

Q=B

Quantum Cost of Toffoli Gate is 5

Working Principle of Quantum Circuit…

Alternate representation of Quantum circuit of TG…

B

AA

B

C AB C

TGAB

C

P=A

R=AB C

Q=B

V

A

B

C V V+ R=AB C

P=A

Q=B

Fig. 9: Quantum Realization of NFT Gate (QC= 5)

V V+V

a

bc

a bac bc

ac bc

Proposed Quantum Circuit of NFT

A

BC

P=A B

R=AC’ BC

Q=AC’ B’CNFT

Proposed Quantum Circuit of NFT…

P=A B

R=AC’ AB

Q=AC’ B’C

A

BC

P=A B

R=AC’ BC

Q=AC’ B’CNFT

P=A B

R=C(A B) A

Q=C(A B) A C

Proposed Quantum Circuit of NFT…

A

BC

P=A B

R=C(A B) A

NFT Q=C(A B) A C

A

BC

A BBC

Proposed Quantum Circuit of NFT…

A

BC

P=A B

R=C(A B) A

NFT Q=C(A B) A C

A

BC

A B

CC(A B) B

Proposed Quantum Circuit of NFT…

A

BC

P=A B

R=C(A B) A

NFT Q=C(A B) A C

ABC

A BC(A B) BC B A

Proposed Quantum Circuit of NFT…

A

BC

P=A B

R=C(A B) A

NFT Q=C(A B) A C

ABC

A BC(A B) BC(A B) A C

Proposed Quantum Circuit of NFT…

A

BC

P=A B

R=C(A B) A

NFT Q=C(A B) A C

ABC

A BC(A B) A CC(A B) B

Proposed Quantum Circuit of NFT…

A

BC

P=A B

R=C(A B) A

NFT Q=C(A B) A C

ABC

A BC(A B) A CC(A B) A

Fig. 9: Quantum Realization of NFT Gate (QC= 5)

V V+V

a

bc

a bac bc

ac bc

Proposed Quantum Circuit of NFT

A

BC

P=A B

R=AC’ BC

Q=AC’ B’CNFT

Fault Tolerant Mechanism

Fault Tolerant Mechanism

Preserves same parity between Input and Output vectors

over one to one mapping of Reversible circuit.

Reversible Circuit

I1

I2

I3

In

O1

O2

O3

On

EV

EN

Par

ity

EV

EN

Par

ity

Reversible Circuit

I1

I2

I3

In

O1

O2

O3

On

OD

D P

arit

y

OD

D P

arit

y

Fig. 10: Fault Tolerant circuit preserves same parity between input and output vectors

[4] B. Parhami, “Fault tolerant reversible circuits,” in In Proc. of 40th Asimolar Conference Signals, Systems and Computers. Pacific Grove, CA, 2006, pp. 1726–1729.

Fault Tolerant Mechanism...

Let, Iv and Ov are input and output vectors of a reversible

circuit, so the relation is Iv↔Ov.

But to be a Reversible Fault Tolerant circuit, itself must

preserve following equation:

where Iv={I1, I2, I3, …, In} and Ov={O1, O2, O3, …, On}

nn OOOIII 2121

Input Parity = Output Parity

Fault Tolerant Mechanism…

A

BC

P=A

R=A’C AB

Q=A’B ACFRG

A

BC

P=A B

R=AC’ BC

Q=AC’ B’CNFT

F2GA

BC

A

A C

A B ABC

P = A

D

Q = A BR = AB CS = AB’ D

MIG

A

B

C

B C D

D

PPHCG B C AB D AC D A

Fig. 11: Most Popular Fault Tolerant Gates

Fault Tolerant Mechanism…

A

BC

P=A

R=A’C AB

Q=A’B ACFRG

RQPCBA

INPUT OUTPUT

A B C P Q R

0 0 0 0 0 0

0 0 1 0 0 1

0 1 0 0 1 0

0 1 1 0 1 1

1 0 0 1 0 0

1 0 1 1 1 0

1 1 0 1 0 1

1 1 1 1 1 1

Fault Tolerant Mechanism…

1

01

1FRG 1

0EV

EN

EV

EN

Fault detection of FRG gate

RQPCBA

Verification of the following equation:

1

01

1FRG 1

1EV

EN

OD

D

Circuit with Faulty OutputCircuit without Fault

Fault Tolerant Mechanism…

A

BC

P=A

R=A’C AB

Q=A’B ACFRG

A

BC

P=A B

R=AC’ BC

Q=AC’ B’CNFTF2GA

BC

A

A C

A B

ABC

P = A

D

Q = A BR = AB CS = AB’ D

MIG

QC= 2

QC= 7

QC=5

QC= 5

Proposed Design of Adder Circuits

F2G F2G NFT F2Ga

b0

0 cin

a b cinab bcin acin

GGG

Proposed Design of Full Adder

CinFRG

F2GF2G

F2G

0

A

B

0

G

G

GA B Cin

AB BCin ACin

Reversible Fault Tolerant Full Adder

2

2 2

5

2 2 5 2

Fig. 12: Proposed Design of Fault Tolerant Adder Circuit

Comparison with Existing Design

ABCD G

MIGSum

MIGCin

CoutG

G

Comparison with Existing [5] Fault Tolerant Design

7 7

F2G F2G NFT F2Ga

b0

0 cin

a b cinab bcin acin

GGG2 2 5 2

Single NFT Full Adder

SNFA[5] M. S. Islam, M. M. Rahman, Z. begum, and M. Z. Hafiz, “Efficient approaches for designing fault tolerant reversible carry look-ahead and carry-skip adders,” MASAUM Journal of Basic and Applied Sciences, vol. 1, no. 3, 2009.

Proposed Design of Carry Skip Adder

Reversible Fault Tolerant Carry Skip Adder (RFT-CSA)

SNFA

x3y3 00

SNFA

x2y2 00

SNFA

x1y1 00

SNFA

x0y0 00

C2 C1C0 Cin

C3

FRG FRG FRG

FRG

0

0

S1S2S3

S000

F2G

Cout

Fig. 13: Proposed Design of Fault Tolerant Carry Skip Adder

Delay Calculation of RFT-CSA

Delay Optimization of Fault Tolerant Carry Skip Adder

SNFA

x3y3 00

SNFA

x2y2 00

SNFA

x1y1 00

SNFA

x0y0 00

C2 C1C0 Cin

C3

FRG FRG FRG

FRG

0

0

S1S2S3

S000

F2G

Cout

4

56789

Fig. 14: Delay Calculation of RFT-CSA

Performance Analysis of RFT-CSA

0

20

40

60

80

100

120

140

Proposed Existing [5] Exising [6] Existing [7]

Un

it(s

)

Gates Garbage Delay Quantum Cost

Fig. 15: Compare with existing designs of Carry Skip Adder[6] P. K. Lala, J. P. Parkerson, and P. Charaborty, “Adder designs using reversible logic gates,” WSEAS TRANSACTIONS on CIRCUITS and SYSTEMS, June 2010.[7] J. W. Bruce et al., “Efficient adder circuits based on a conservative re-versible logic gates,” in ISVLSI ’02: Proceedings of the IEEE Computer Society Annual Symposium on VLSI. Washington, DC, USA, 2005, pp. 83–88.

Proposed Carry Look-ahead AdderReversible Fault Tolerant Carry Look-ahead Adder

(RFT-CLA) Circuit

F2G F2G NFT F2Gx0

00

cin

S0

G

G

F2G F2G NFT F2G0

S1

G

G

y0

x1

0y1

G

G

F2G F2G NFT F2G0

S2

G

G

x2

0y2

G

F2G F2G NFT F2G0

S3

G

G

x3

0y3

G

Cout

Fig. 16: Proposed design of Fault Tolerant Carry Look-ahead Adder

Delay Calculation of RFT-CLA

Delay Calculation of Fault Tolerant Carry Look-ahead Adder

F2G F2G NFT F2Gx0

00

cin

S0

G

G

F2G F2G NFT F2G0

S1

G

G

y0

x1

0y1

G

G

F2G F2G NFT F2G0

S2

G

G

x2

0y2

G

F2G F2G NFT F2G0

S3

G

G

x3

0y3

G

Cout

1 2 3

4

5

6 7

Performance Analysis of RFT-CLA

0

10

20

30

40

50

60

70

RFT-CLA RFT-CSA

Un

it(s

) Gates

Garbage

Delay

Quantum Cost

Fig. 17: Performance Analysis between Fault Tolerant Carry Look-ahead Adder and Carry Skip Adder

Conclusions

Reversible Circuit prevents power consumption caused by

input bit loose and tolerates bit error by using fault tolerant

mechanism. The operations of Quantum Computing are

fundamentally reversible and circuit performs multiple

operations in single cycle. We have presented the efficient

designs of fault tolerant reversible adder circuits, where the

designs are preferable for quantum computing because of

minimum quantum cost in the designs.

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