Remote connections? Detangling entanglement in quantum physics

Quantum computers, quantum cryptography and quantum (insert name here) are often in the news these days. Articles about them inevitably refer to entanglement, a property of quantum physics that makes all these magical devices ...

Quantifying how much quantum information can be eavesdropped

Summary The most basic type of quantum information processing is quantum entanglement. In a new study published in EPJ B, Zhaonan Zhang from Shaanxi Normal University, Xi'an, China, and colleagues have provided a much finer ...

Physicists reveal material for high-speed quantum internet

Researchers from the Moscow Institute of Physics and Technology have rediscovered a material that could be the basis for ultra-high-speed quantum internet. Their paper published in npj Quantum Information shows how to increase ...

Trust is good, quantum trickery is better

An international team of scientists has proven, for the first time, the security of so-called device-independent quantum cryptography in a regime that is attainable with state-of-the-art quantum technology, thus paving the ...

A newly discovered prime number makes its debut

On December 26, 2017, J. Pace, G. Woltman, S. Kurowski, A. Blosser, and their co-authors announced the discovery of a new prime number: 2⁷⁷²³²⁹¹⁷-1. It's an excellent opportunity to take a small tour through the ...

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Quantum cryptography

Quantum cryptography, or quantum key distribution (QKD), uses quantum mechanics to guarantee secure communication. It enables two parties to produce a shared random bit string known only to them, which can be used as a key to encrypt and decrypt messages.

An important and unique property of quantum cryptography is the ability of the two communicating users to detect the presence of any third party trying to gain knowledge of the key. This results from a fundamental aspect of quantum mechanics: the process of measuring a quantum system in general disturbs the system. A third party trying to eavesdrop on the key must in some way measure it, thus introducing detectable anomalies. By using quantum superpositions or quantum entanglement and transmitting information in quantum states, a communication system can be implemented which detects eavesdropping. If the level of eavesdropping is below a certain threshold a key can be produced that is guaranteed to be secure (i.e. the eavesdropper has no information about), otherwise no secure key is possible and communication is aborted.

The security of quantum cryptography relies on the foundations of quantum mechanics, in contrast to traditional public key cryptography which relies on the computational difficulty of certain mathematical functions, and cannot provide any indication of eavesdropping or guarantee of key security.

Quantum cryptography is only used to produce and distribute a key, not to transmit any message data. This key can then be used with any chosen encryption algorithm to encrypt (and decrypt) a message, which can then be transmitted over a standard communication channel. The algorithm most commonly associated with QKD is the one-time pad, as it is provably secure when used with a secret, random key.

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