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Sheer Curiosity

Scott Aaronson summarized it well: it would be astonishing if we learned nothing new by studying the intersection of quantum mechanics and computation

The final motivation for building quantum computers is certainly the most fundamental: sheer curiosity.

Scott Aaronson, professor at the University of Texas at Austin, said in his Ph.D. thesis, back in 2004:

For me, quantum computing matters because it combines two of the great mysteries bequeathed to us by the twentieth century: the nature of quantum mechanics, and the ultimate limits of computation. It would be astonishing if such an elemental connection between these mysteries shed no new light on either of them.
Quantum computing and quantum information owe their origins in part to the dissatisfaction with an apparent contradiction between the quantum mechanics of the first half of the twentieth century and special relativity, which limits the movement of any physical object to the speed of light. This worried Albert Einstein, Boris Podolsky and Nathan Rosen, who proposed a thought experiment highlighting the fact that two quanta seem to communicate with each other instantaneously, regardless of distance. In the 1960s, John Bell proposed a statistical test for whether this can happen.
Quantum computing proper began as a purely intellectual exercise in the 1980s, with important thinkers such as Richard Feynman, David Deutsch, Paul Benioff, and Charles Bennett striving to understand how the equations that govern our universe affect what can and cannot be computed efficiently.
At the same time, experimental physicists such as David Wineland, Serge Haroche, Alan Aspect and a host of others were pushing the boundaries of our ability to control and manipulate individual atoms, electrons, photons and tiny amounts of electrical current. They built exquisitely precise atomic clocks and other measurement apparatuses to test theoretical predictions about fundamental physics, then turned their attention to determining how to build a quantum computer.
Thanks to Bell’s theory and an increasingly rigorous set of experiments that confirm its truth, we now understand that information cannot travel faster than light. The exact resolution of why and how Einstein’s “spooky action at a distance” arises is an open topic in the foundations of quantum mechanics, but we will learn more about this quantum entanglement later in this course.
Thus, we can say that building a quantum computer is also a fascinating and important scientific experiment in its own right. It would be surprising if we learned nothing new in the process!


私が量子計算について気になる理由は、量子計算が20世紀から残されている2つの大きな謎を結びつけているからです。 それは、量子力学の性質と、計算の最終的な限界です。 2つの謎の間の要素的なつながりが、どちらかもしくは両方の謎に新しい光を当てるのであれば、それは驚くべきことです。

量子計算と量子情報は、20世紀前半の量子力学と、物体の動きを光の速度以下に制限する特殊相対性理論との間に、明らかな矛盾が存在しているという不満に始まります。 不満を持っていたアルベルト・アインシュタイン、ボリス・ポドルスキー、ネイサン・ローゼンは、2つの量子が距離にかかわらず瞬間的に相互作用を起こすという事実を強調する思考実験を提案しました。 1960年代、ジョン・ベルはこれが起こるかどうかの統計的テストを提案しました。


同時に、デービッド・ワインランド、セルジュ・アロシュ、アラン・アスペなどの実験物理学者たちは、個々の原子、電子、光子、微量の電流を制御・操作する能力の限界を向上させていました。 彼らは精密な原子時計やその他の測定装置を構築して、基本的な物理に関する理論的予測をテストした後、量子コンピュータを構築する方法の研究に移っていきました。

ベルの理論と、それを裏付ける厳格な一連の実験技術の進歩のおかげで、我々は情報が光よりも速く進むことができないことを理解しています。 なぜ、どのようにアインシュタインの「不気味な遠隔作用(spooky action at a distance)」が起きるのかという問いの正確な解は、量子力学の基礎理論では未解決ですが、私たちはこのコースの後半でこの「量子もつれ」について更に詳しく学んでいきます。

このように、量子コンピュータを構築することは、それ自体が魅力的で重要な科学的実験であるともいえます。 この過程で、人類は確実に新しいことを学ぶことができるはずです。

© Keio University
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