August 2020
Beginner to intermediate
332 pages
8h 16m
Japanese
book
動かして学ぶ量子コンピュータプログラミング ―シミュレータとサンプルコードで理解する基本アルゴリズム
by Eric R. Johnston, Nic Harrigan, Mercedes Gimeno-Segovia, 北野 章, 丸山 耕司
Content preview from 動かして学ぶ量子コンピュータプログラミング ―シミュレータとサンプルコードで理解する基本アルゴリズム
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12.2
ショアのアルゴリズムが行うこと
235
12.2.1
本当に
QPU
は必要か？
私たちは、素因数分解の問題を、
a
x
mod(N)
の周期
p
を見つける問題に還元しました。実は、この
問題は従来型の
CPU
を使ったプログラムでも解くことができます。
x
の値を大きくしながら
a
x
mod(N)
を繰り返し評価し、試した
x
の値の数を数えながら、計算される値を観測していくことで、
p
を求める
ことができます。値が返されたら計算を終了し、そのときの整数値
x
がその周期となります。
a
x
mod(
N
)
の周期を見つけるというこの力任せの方法（
brute-force method
）で は 、 こ の 関
数の値が同じ値をとったときに、反復周期
p
に到達したと仮定しています。この仮定が正し
いかどうかは自明というわけではありませんが、数学的には
a
x
mod(
N
)
は
1
周期に
1
回、決
まった値とることを証明することができます。このため、等しい値が
2
回得られた瞬間に
1
回目の周期が終わったと言えるので、この方法で周期
p
を決定することができます。
例12-2は
p
を計算するために、従来型の
CPU
を使った力任せの方法の実装例です。
サンプルコード
https://oreilly-qc.github.io?p=12-2
で例12-2を実行してみましょう。
例 12-2
function ShorNoQPU(N, precision_bits, coprime) {
// Classical replacement for ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.