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This Defense Intelligence Reference Document from the Defense Intelligence Agency, dated 10 December 2010, is one of a series of advanced technology reports produced in FY 2010 under the Advanced Aerospace Weapon System Applications (AAWSA) Program. It reviews quantum computing technologies and DNA-based molecular computing for onboard supercomputing on future spacecraft. It forecasts ion-trap quantum computers within 10 years, simple DNA tile computing within 20 years, and self-repairing DNA computers on a 40-year horizon.
“Strand”15 pages
UNCLASSIFIED//POI\ GI I ICIAL USE 014Jtf APPLICATIONS OF QUANTUM COMPUTERS Although smaller circuitry and supercomputing is a motivator, the driving application behind quantum computing is cryptography. First, there is cracking cipher codes. The vast majority of secured communications utilize a method known as public-key cryptography. In this method, the code is based on the prime number factors of a very large integer which is publically available. The private key is one of the integer factors and this allows the receiver of information to decipher the code easily. The strength of this technique is that traditional computer algorithms will take a long time to guess the correct factors of the public key, on the order of months.9 Traditional brute force methods require a number of steps that increase as an exponential function of the size of the public key. However, in 1994 Shor presented a quantum algorithm that would only require a polynomial number of steps, thus dramatically decreasing the required time to factor, assuming a quantum computer would ever be physically realized. (6) This speedup is primarily due to the nature of quantum waves; specifically, they can follow several parallel paths instead of the usual stepwise procedural execution of instructions. This acceleration by superposition concept is more easily understood in a random search of data. Consider an algorithm that has a 50% probability to locate a specific phone number in a database of N phone numbers by a random search. The procedural algorithm on average will require O.SN inquiries to locate the correct number. A quantum algorithm on the other hand can be devised that accumulates information by examining multiple numbers with each step. Such a scheme has been shown to reduce the number of examinations required to ✓N. (7, 8) The superposition of states allows examination and processing of several tape cells simultaneously in a Turing-inspired machine. Second, there is quantum communication. Once public key encryption is easily broken by the quantum computer, a new cipher needs to replace it. The canonical quantum communication experiment defines a sender, Bob, and a receiver, Alice. In most scenarios, Alice and Bob communicate over a distance using entangled particles and a traditional open line. The open line relays information about measurement settings, but is useless to an observer without access to the entangled wave function (entanglement is discussed below, and the open line information is an analogue to the public key of current ciphers). The other advantage of this setup is that almost any disturbance in the communication line between Alice and Bob would destroy entanglement and thus the information would be lost instead of intercepted. Additional archetypical participants in a communications experiment/scenario follow the English alphabet: Charlie (or Chuck if his intent is malicious), Dave, Eve, etc. Quantum communication is thus an application replacing one performed by a general purpose computing machine; the classical and quantum systems do not operate in similar fashion other than the function of securely transmitting information. Additionally, quantum communication has been suggested as a method to connect isolated quantum systems without disturbing closed box requirements like classical interventions would. (9, 10) Beyond cryptography is a third application, quantum metrology, where time and/or distance are measured to an extremely high accuracy. A fourth obvious application is simulation of quantum systems. (11, 12) g Or hours if one has farms of supercomputers. The point is that the value of most communication is much smaller than the cost to decipher by brute force. The 128-bit web standard is a compromise between security and speed. 10 UNCLASSIFIED/;'f8R: 8ffl@IJliL ~81!! 8HLY
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Report, from the dia collection. The PDF is mirrored here; the original link is under it. 54 pages are in the text index: search them above, or from the library's search.