Download presentation

Published byKatlyn Collinge Modified over 3 years ago

1
**prime factorization algorithm found by Peter Shor 1994**

generalized to an algorithm for order finding key step is the quantum Fourier transform (QFT)

2
**discrete Fourier transform (DFT)**

Lieven Vandersypen, PhD thesis: DFT unitary transform that converts a string of N complex numbers xj to a string of N complex numbers yj yk = xj ei2pjk/N 1 √N ∑ j=0 N-1 inverts periodicity (input string period r, output string N/r) converts off-sets into phase factors 1 0 -i i 0

3
**quantum Fourier transform**

Lieven Vandersypen, PhD thesis: number of qubits n = log2 N (for N=8, three qubits) amplitude of |000 represents first complex number, |001 the 2nd states |000, |001, ... , |111 are labelled |0, |1 , ... , |7 |j → ei2pjk/N |k 1 √N ∑ k=0 N-1 1 0 -i i 0 (|1 + |5)√2 (|0 - i|2 - |4 + i|6)/2

4
**quantum Fourier transform**

|j → ei2pjk/N |k 1 √N ∑ k=0 N-1 (short: j = j1j2j3) j = j122 + j221 + j320 0.j1j2j3 = j1/2 + j2/4 + j3/8 reverse order of output qubits: j1in = j3out, j3in = j1out e |j1 j2 j3 → 1 2n/2 |0 + 2pi 0. |1 j3 j1 j2j1 j2j3 j3j2j1 j1j2j3 1 -1 √2 j3in 1 -1 √2 j2in 1 eip/2 j2in j3in =1 H R23 90° H

5
**QFT quantum circuit |j3 |j2 |j1 |j1 |j2 |j3 H R R H R H e H = p**

Weinstein et al.: quant-ph/ v1 (1999) |j3 |j2 |j1 |j1 |j2 |j3 H R 90° R 45° H R 90° H -i f 2 e i H = i ħ Ix p e Iy 2 i ħ Iz f e R1 = = i ħ Iyj,k p 2 e Iyj,k Ixj,k f i ħ Iy p 2 e Iy Ix f = Rjk= i ħ J t Izj Izk e Iq j p

6
QFT implementation Weinstein et al.: Phys. Rev. Lett. 86,1889 (2001) 13C labeled spins of Alanine as qubits (T1>1.5s, T2>400ms) Preparation of pseudo-pure state |000 Preparation of input state |000+|010+ |100+|110 Apply QFT => |000+|001 and SWAP => |000+|100 |111 000| |000 000| |111 111| |000 111|

7
**Order finding M rooms with one entrance and one exit**

Lieven Vandersypen, PhD thesis: M rooms with one entrance and one exit Connected by subcycles How often to change room until back at start? p1(5)=4, p2(5)=2, … 6 y={2,4,5} 7 r=3 y={0,1,3,7} 4 r=4 y=6 r=1 5 2 3 1

8
**Order finding: quantum circuit**

Lieven Vandersypen, PhD thesis: |x= |x2x1x0, x=4x2+2x1+x0 M=4, |y1y0= |y, y M-1 |x|y → |x|px(y) = |x|p4x (y)|p2x (y)|px (y) 2 1 y=3 p1(3)=1, p2(3)=3, … |0 H QFT p4(y) p2(y) p (y) |y1 |y0 |1 |y2=(|0+|2+|4+|6)|1+(|1+|3+|5+|7)|3 |y1=(|0+|1+|2+|3+|4+|5+|6+|7)|11 |y3=(|0+|4)|1+(|0-|4)|3 |y0=|000|11 measurement yields multiple of 2n/r => r=2

9
**Order finding for n qubits**

Lieven Vandersypen, PhD thesis: register 1 register 2 number of transitions between “rooms” number of starting room 1) |0|0 2) Hn → √2n 1 S |j|0 j=0 2 -1 n 3) f(j)=pj(0) → √2n 1 S |j|f(j) j=0 2 -1 n 4) QFT r1 → ei2pjk/N |k|f(j) → ei2pjk/N |k|f(j) √2n 1 S j=0 2 -1 n k=0 5) Measure the amplitude of |k → S ei2pjk/N j=0 2 -1 n 2 (large for k=c*N/r)

10
**Shor’s algorithm number to factorize: N (e.g. N=15)**

L. Vandersypen et al.: Nature 414, 883 (2001) number to factorize: N (e.g. N=15) one factor is gcd(ar/21,N) (probability >0.5) “easy” integer a does NOT divide N (a=2,4,7,8,11,13,14) “easy?” f(x,y)=px(y)=axy mod N a2 mod 15 = 1, a {4,11,14} f(x) needs x0 only a4 mod 15 = 1, a {2,7,8,13} => a mod 15 =1, k ≥ 2 2k f(x) needs x0 and x1 register 1 needs 2 qubits (take 3) n=2m register 2 needs 4 qubits m=(log2N)

11
**Implementation of Shor’s algorithm**

1 2 3 4 5 6 7 C

12
**Measurement thermal spectra a=11 effective pure state calculated**

measured simulated x0=0 x1=0 x2=|0+|1 x=|000+|100 =|0+|4 =>r=2n/4=2 gcd(112/21,15)=3,5

13
**Pulse sequence total ~300 pulses 90°pulse 180°refocusing pulses**

y -x x 90°pulse 180°refocusing pulses x -x z rotation

Similar presentations

OK

15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 $1 Million $500,000 $250,000 $125,000 $64,000 $32,000 $16,000 $8,000 $4,000 $2,000 $1,000 $500 $300 $200 $100 Welcome.

15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 $1 Million $500,000 $250,000 $125,000 $64,000 $32,000 $16,000 $8,000 $4,000 $2,000 $1,000 $500 $300 $200 $100 Welcome.

© 2018 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Ppt on general etiquettes of life Ppt on conservation of electrical energy Upload and view ppt online ticket Ppt on index numbers line Ppt on next generation 2-stroke engine fuel Ppt on manufacturing of soft drinks Holographic 3d display ppt on tv Ppt on acid-base indicators chemistry Ppt on amplitude shift keying demodulation Download ppt on school management system