 |
Business | Industries | Finance | Tax |
| Index: > A B C D E F G H I J K L M N O P Q R S T U V W X Y Z |
|
|||||
| First Prev [ 1 2 3 ] Next Last |
The basic idea in quantum key exchange is to use the "noisy" properties of light to render incoherent an image that acts to complement a secret key. This image can be represented in a number of ways, but the ability to decode that image rests upon an understanding of how it was made. No way to intercept the transmission without changing it is possible, so key information can be exchanged with great confidence it has been transmitted secretly.
Using quantum superposition as a part of the computation, quantum computing will considerably extend the reach of cryptanalysis, making brute force key space searches much more effective -- if such computers ever become possible in actual practice.
This is a particular approach to cryptography which appears to offer a very secure, albeit expensive, and low data rate, communications channel.
The most straightforward application is in distribution of secret keys. The rate of transmission will likely be low, for technical reasons, but the transmission will be secure at our present understanding of quantum mechanics. No informed observer has suggested any way around this; it is widely believed there can be no such way. By taking advantage of existing high quality encryption algorithms, this initial secure transfer can be leveraged to achieve a subsequent secure transmission of large amounts of data (at much higher speeds). Quantum key exchange may, thus, become an excellent alternative to the Diffie-Hellman key exchange algorithm.
The advantage of quantum key exchange over traditional key exchange methods is the certainty that the key exchange cannot be compromised. The exchange can be shown to be secure in a very strong sense, without relying on the intractability of one or more mathematical problems. Even assuming eavesdroppers with unlimited computing power and funding, the laws of quantum physics guarantee (though only probabilistically) that the key exchange will be secure, given a few other assumptions.
The information is exchanged by observations of quantum states. Typically photons are put into a particular state by the sender and then observed by the recipient. Because of Heisenberg's uncertainty principle, certain quantum informationQuantum information is physical information that is held in the "state" of a quantum system. The most popular unit of quantum information is the qubit, a two-state quantum system. However, unlike classical digital states (which are discrete), a two-state occurs as conjugates (superposition) that cannot be simultaneously measured. Depending on how an observation is carried out, different aspects of the system can be measured -- for example, polarizationThis article treats polarization in electrodynamics. Other articles treat polarization in electrostatics, polarization in politics and polarization in psychology. In electrodynamics, polarization is a property of waves, such as light and other electromagns of photons can be expressed as any of three different types: rectilinear, circular, and diagonal -- but every observation of those photons (including by any eavesdropper) changes the values of the conjugates. Thus, if the receiver and sender do not agree on what basis of a quantum system they are using as bases, the receiver or eavesdropper will destroy the sender's information without gaining any useful information, and, depending on the protocolsIn computing, a protocol is a convention or standard that controls or enables the connection, communication, and data transfer between two computing endpoints. Protocols may be implemented by hardware, software, or a combination of the two. At the lowest being used, may betray his/her presence.
Ideally, each pulse should consist of a single photon. If this is impossible, and the number of photons received is Poisson-distributedIn statistics and probability theory, the Poisson distribution is a discrete probability distribution (discovered by Simeon-Denis Poisson ( 1781- 1840) and published, together with his probability theory, in 1838 in his work Recherches sur la probabilite, the average number of photons in each pulse should be slightly larger than the logarithmIn mathematics, the logarithm functions are the inverses of the exponential functions. Logarithms are numbers that are substituted in computation for other numbers, to which they bear such a relation that the operations to be performed on the latter are r of the number of bitThis article is about the unit of information, see Bit (disambiguation) for other meanings. A bit (abbreviated b is the most basic information unit used in computing and information theory. A single bit (short for b inary dig it is a zero or a one, or a ts in a message. Fewer, and a pulse may be absent; more, and the polarization of a pulse can be detected without altering it.
| Politics | Business | Finance |
 |
 |
 |
|