Orbital Angular Momentum in Quantum Communication and Information

Xizheng Ke, Hong Lv, Jingzhi Wu +1 more

The beam with orbital angular momentum is a present domestic and foreign research key direction. Its application and development will bring the profound influence in the optical communications field. At the same time, light's orbital angular momentum promises potential applications in both classical and quantum optical communication. The research progress of the beam with orbital angular momentum and encoding information as light's OAM for free-space optical communication were reviewed in this article, the existing design method, mechanism and description methods of encoding information as light's OAM were discussed. In quantum communication, qudits can be encoded in photons using their OAM for creating high-dimensional entanglement based on entangled photon pairs from SPDC. In this paper, light's OAM is used as information carrier for classical and quantum communication, which is promising to ensures the security of atmospheric laser communication, improves the density and precision of information transmission. It is apparent that an efficient way to measure the orbital angular momentum of individual photons and light beams with good efficiency would be of potentially great importance for optical communications and quantum information. In view of the above, the measurements of orbital angular momentum of individual photons and light beams are analyzed and discussed in detail.

Jean-Marc Lévy-Leblond

郭建军 Guo Jianjun, 郭邦红 Guo Banghong, 程广明 Cheng Guangming +3 more

Xizheng Ke

The nondiffracting higher-order Bessel beams carry the orbital angular momentum(OAM). During free propagation,their transverse intensity profile remains nearly invariant in a range.The beam comprises the topological charge l helical phasefronts and carries an orbital angular momentum of lh per photon.The angular momentum number carried by the photon in each eigenmode is represented by l, and the eigenstates |l〉can generate multidimensional quantum entangled states.A method of optical communication is presented that encodes information in two orthogonal orbital angular momentum states based on higher-order Bessel beams.Each photon carries OAM states of information,which can increase the key generation rate of the protocol,and offer a quantum solution for increase of the optical communication distance.

Hong Lai, Liling Zhang, Yanrong Zhu

The existing quantum secure direct communication (QSDC) protocols mainly make use of the spin angular momentum and entangled photons, to realize direct transmission of confidential information. But those protocols' capacity is low, only one-bit information. On the other hand, the orbital angular momentum (OAM) of a photon can be theoretically evaluated from minus infinity to infinity, and the angular momentum states of different orbits are orthogonal to each other. Given that, in this paper, we propose a quantum secure direct communication scheme based on OAM. Specifically, taking OAM of photons as the information carrier, the data of information is segmented and high-capacity coding in quantum secure direct communication is realized through the segmentation of sector states.

Ajit Kumar