Quantum Pioneer Stephen Wiesner

by Lawrence Klaes, Science Editor

The year 1969 was certainly a time for landmark events in human history. Some are of course incredibly well known, such as the first manned landing on the Moon by the crew of Apollo 11 in July of that year. Another involved the New York Mets winning Major League Baseball’s World Series just a few months later.

There were also several other major events of a historic nature that happened in 1969 which did not receive anywhere near the same amount of publicity. One reason for this is that two of these revolutionary ideas involved the highly refined science of quantum physics. Another reason was due to these ideas being far ahead of contemporary understanding.

One concept involved the very creation of the Universe itself with a hypothesis called Vacuum genesis. Physicist Edward Tryon (1940 – 2019) apparently came up with the idea while attending a seminar on quantum physics in 1969. As cosmologist Dennis Sciama (1926 – 1999) was giving a lecture there, Tryon had a sudden inspiration and said out loud “Maybe the Universe is a vacuum fluctuation!”

The seminar audience thought Tryon had merely made an amusing quip, but in fact he was thinking of how virtual energetic particles can emerge into reality from quantum vacuum fields, or literally empty space, for short periods of time before returning to a state of non-existence. While Tryon’s idea has yet to be either proven or disproven by science, it does represent one scientifically plausible scenario to explain why and how our Universe came into existence from apparent nothingness.

The other landmark happening in 1969 (and thereabouts) involving quantum physics was even more historically obscure and unappreciated at the time but has since grown into perhaps the founding moment of what is now known as quantum cryptography.

A fellow named Stephen J. Wiesner was attending graduate school at Columbia University and exchanging ideas with his friend Charles Henry Bennett (born 1943) of Harvard University. Among Wiesner’s thoughts were on the concepts of quantum money and quantum multiplexing.

An age-old problem is the need for societies to protect their currency from counterfeiting and their critical knowledge and information from falling into the wrong hands. In the past, information encryption involved the generation of very large amounts of numbers, which had to be mathematically taken apart and reassembled in the proper order to allow items to be identified and data to be read. Understandably, this process was both time and space consuming, even when standard computers were involved.

Wiesner came up with a way to circumvent these large numbers with the idea of encoding paper money with light traps. He envisioned just twenty such devices on each bill that would be able to capture a single randomly polarized photon each, identifying the bank note with a unique serial number. As only a suitably equipped bank would possess the technology to read the exact sequence determined by quantum physics, a would-be counterfeiter could never produce a bill that would match the exact numbers required to pass as a real monetary note.

Here is a basic idea of what Wiesner’s concept of quantum money would look like. The little squares with the arrows represent the light traps that make counterfeiting impossible.

The quantum money concept led into Wiesner’s other idea, quantum multiplexing. In its most basic form, one party sends multiple messages to a receiver who is presumed to know exactly which message to decode and read. Whichever one they chose will cause the other messages to be destroyed without the chance of recovery. If an unwelcome party tried to read the messages without the proper exact codes, this too would cause the transmitting information to irreversibly destruct. This remarkable idea would one day lead to the emergence of the field known as quantum information science and the ability to send entangled transmissions across large distances.

Wiesner and his initial ideas suffered from one major flaw: They emerged in an era where utilizing such quantum abilities were beyond not only the technologies of the day but the minds of most people, even the ones who had the potential to grasp such concepts.

The graduate student wrote a paper on his ideas which he titled “Conjugate Coding”. The response from his fellow academics was less than enthusiastic.

“I didn’t get any support from my thesis advisor – he showed no interest at all,” Wiesner would later report. “I showed it to several other people, and they all pulled a strange face, and went straight back to what they were already doing.”

It would be safe to say that Wiesner was trying to explain the equivalent of a nuclear power plant to residents of the early Nineteenth Century: They had the general idea of atoms and atomic structure, but virtually no comprehension of their potential for human civilization. To use a well-worn phrase, Wiesner was way ahead of his time.

Later on, Wiesner would submit “Conjugate Coding” to the publication IEEE Transactions on Information Theory. They too rejected his paper as Wiesner had written it much like a physics paper and the benefits (and specific languages) of cross-disciplinary fields were often not as well appreciated then.

Eventually Wiesner’s landmark paper would be published in 1983 in SIGACT News, 15 (1): 78-88. Thankfully by then, the physicist’s past friendship and correspondence with Charles Bennett had paid off: Not only did Bennett relay Wiesner’s pioneering accomplishments to the world and history, but he was inspired to carry on his friend’s ideas to further various fields in quantum physics and mechanics.

One tangible benefit from all this became the implementation and eventually practical applications of Wiesner’s original concepts. Bennet and Gilles Brassard (born 1955) would go on to produce the first protocol for quantum cryptography in 1984, followed by the first experimental prototype in 1991.

By the early Twenty-First Century – April of 2004, to be exact – funds encrypted by quantum keys were successfully transferred between two nearby banks in Austria for the first time. A mere two months later, the first quantum cryptographically-secured computer network was operating in Cambridge, Massachusetts, between BBN and Harvard.

Quantum communications and computing have certainly come a long way since Stephen Wiesner first elaborated upon his ideas half a century ago. Thankfully, not only were his ideas scientifically and technologically plausible, they stand ready to promote widespread change in the way our civilization functions. When this day comes, this quantum pioneer will undoubtedly and deservedly join the ranks of the well-known scientists and similar men and women who advanced humanity into the future.

Wiesner’s landmark paper, “Conjugate Coding”, is available to read online for free here:

http://users.cms.caltech.edu/~vidick/teaching/120_qcrypto/wiesner.pdf

I also recommend this paper on the history of quantum cryptography written by Gilles Brassard himself:

https://arxiv.org/abs/quant-ph/0604072

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