The New Quantum Era

Chapter 5. Gedankenexperiment

Ordinary classical information, such as one finds in a book, can be copied at will and is not disturbed by reading it. Quantum Information is more like the information in a dream. Recalling a dream and describing it to someone else inevitably changes your memory of it. But unlike dreams, quantum information obeys well-known laws.

Charles H. Bennett¹

Turing’s information theory had been turned into a realized technology by teams working at Princeton and the University of Pennsylvania in order to aid in the calculations needed to make quantum theory into a terrible weapon. After the war, the focus for those building computers was for applications of a less destructive nature, and so fields of information science and physics headed off, for the most part, in different directions. Quantum physics was there to help create the semiconductor-based integrated circuits and microprocessors, and create the lasers in CD-ROMs and fiber optics, but it had no role in algorithms and applications. That separation would not last long.

It is not usually possible when tracing the development of a scientific theory to find a tidy origin story for a breakthrough. However, this is not the case with quantum computing. The work of Rolf Landauer, a physicist who had joined IBM’s research division in 1952, can be seen as a clear point of origin for the field. Landauer, a Harvard-trained physicist whose family had left Germany to escape Nazism, was interested in the physics ...