High-dimensional quantum key distribution (HDQKD) is a technology for

secure communication Secure communication is when two entities are communicating and do not want a third party to listen in. For this to be the case, the entities need to communicate in a way that is unsusceptible to eavesdropping or interception. Secure communication ...

between two parties. It allows for higher information efficiency than traditional binary

quantum key distribution Quantum key distribution (QKD) is a secure communication method which implements a cryptographic protocol involving components of quantum mechanics. It enables two parties to produce a shared random secret key known only to them, which can then ...

(QKD) protocols, which are limited to 1

bit The bit is the most basic unit of information in computing and digital communications. The name is a portmanteau of binary digit. The bit represents a logical state with one of two possible values. These values are most commonly represented a ...

photon A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are Massless particle, massless ...

. HDQKD also exhibits higher resilience to noise, enabling lower

signal-to-noise ratio Signal-to-noise ratio (SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. SNR is defined as the ratio of signal power to the noise power, often expressed in d ...

s and longer transmission distances.

Implementation

One way to implement HDQKD is by using space division

multiplexing In telecommunications and computer networking, multiplexing (sometimes contracted to muxing) is a method by which multiple analog or digital signals are combined into one signal over a shared medium. The aim is to share a scarce resource - a ...

technology and encoding quantum information in the spatial dimension, such as with optical angular momentum (OAM) modes. While OAM modes have been demonstrated for HDQKD over free-space links, transmission over long-distance

fiber Fiber or fibre (from la, fibra, links=no) is a natural or artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineering materials often incorpora ...

links is challenging due to intermodal crosstalk. An alternative approach is to use multicore fibers (MCFs) with separate cores, which offer a large multiplicity of cores and low crosstalk between cores. However, there are also challenges to implementing HDQKD with MCFs. Manipulating high-dimensional quantum states in MCFs requires precise phase stability, which can be difficult to achieve. In addition, transmitting quantum states through fibers can introduce noise and loss, leading to lower fidelity and higher quantum bit error rates (QBER).

References

{{reflist Cryptographic algorithms Quantum information science Quantum cryptography Quantum cryptography protocols

Implementation

See also

References