Quantum mechanics. To non-scientists and scientists alike, the phrase probably conjures up complex mathematical theory. Easily sidelined as something that exists only in the theoretical realm (a kind of imaginary oddity), recent advancements in quantum theory have made it possible for some aspects of quantum mechanics to be integrated into real-world applications. One hot area of study is cryptography, the study of hiding information (or encryption), as part of quantum communications and computation.
Quantum mechanics is generalized as the study of the principles governing the behavior of atomic and subatomic particles. The fundamentals of quantum mechanics are still subject to debate today, because of the conceptual abnormalities that differentiate them from the rules that govern classical physics. Physicists still puzzle at the theories of quantum mechanics because the natural laws of physics so familiar in explaining everyday behaviors cannot be applied to particles on the smaller scale. So how then is quantum theory applicable in real-world technology? Although there are still many unknowns, scientists can exploit certain features.
To understand how cryptography works within quantum theory, it’s essential to understand certain aspects of quantum mechanics. Quantum cryptography, or quantum key distribution, is unique in that it uses quantum mechanics to ensure secure communication between two parties while also being capable of detecting interference or eavesdropping from a third party. Quantum cryptography uses both the properties of quantum superpositions (which defines the set of all possible states an object could have, or probability theory) and quantum entanglement (which states that a system of two or more objects cannot be described individually without mentioning one in respect to the other) to describe a fundamental aspect of quantum mechanics. In other words, a quantum system cannot be measured without disturbing or interfering with the system.
“To measure which way [an object] behaves, you’d have to interact with it, bounce some photons off of it or something,” explains Professor Aephraim Steinberg of the Department of Physics and the Institute of Optical Sciences. “The idea is that if there’s an electron moving along here and you try to look at it in the microscope, then at some point some photons had to bounce off it and that’s going to change the momentum of the outcome […] so it turns out you can’t measure anything without disturbing it.”
A third party trying to gain access to the communication between the two parties therefore has to, in some way, measure the system, thus disturbing it and creating irregularities detectable to the two original parties.
This implementation of quantum cryptography is not used to transmit messages, but rather to produce a key for accessing messages. One party can transmit a secure key (with no interference from a third party) with an encryption algorithm to relay a message along a standard communication channel.
Current uses for this type of cryptography are primarily aimed at governments and corporations with high security requirements. Quantum cryptography has not reached widespread adoption outside of high-security areas due to high equipment costs, as well as the lack of significant threat to current key exchange protocols. Notable recent implementations of this type of cryptography, however, includes a bank transfer from the Mayor of Vienna to an Austrian bank in 2004 and the creation of Secure Communication Based on Quantum Cryptography, the first computer network protected by quantum cryptography, in 2008.
Quantum computation is another area that utilizes the fundamentals of quantum superposition to create quantum computers, which are essentially super computers capable of computations at a much faster pace than any current computers. Integer factorizations that are practically unsolvable by today’s computers can be calculated by super computers.
Professor Steinberg says “Today’s computers won’t be able to solve these codes, but the computers in 10 years can. So you add a few more digits and it takes another 10 years to come up with computers that can solve those problems. In quantum computation, the addition of one or two more extra digits won’t create much of an effect on the computer’s ability to compute efficiently.”
