On the quantum-channel capacity for orbital angular momentum-based free-space optical communications

Zhang, Yequn; Djordjević, Ivan B.; Gao, Xin

doi:10.1364/ol.37.003267

Cited by 28 publications

(10 citation statements)

References 8 publications

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“…1 can be transmitted either over FMF link or by using an expanding telescope be sent over an FSO link to the remote receiver. When the OAM baseket jli is transmitted over the atmospheric turbulence channel, it can be detected on the receiver side as baseket jl 0 i ðl 0 6 ¼ lÞ with certain probability as we have shown in [37] (see also [32]), which will affect the MQKD protocols over FSO links. On the other hand, due to mode coupling the portion of observed OAM baseket jli will flow to neighboring OAM modes, resulting in crosstalk [38].…”

Section: Multidimensional Qkd Over Few-mode Fiber and Free-space Optimentioning

confidence: 97%

Multidimensional QKD Based on Combined Orbital and Spin Angular Momenta of Photon

Djordjević

2013

IEEE Photonics J.

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It has been widely recognized that the underlying principles of quantum mechanics could be used to enable secure communications, without any additional conventional cryptographic systems, while utilizing the properties of the photons. Considerable research efforts have been invested to develop an efficient quantum key distribution (QKD) scheme over either free-space optical or fiber-optics channels. Most of these research efforts have been focused on a two-dimensional QKD, commonly realized by the use of the polarization state of photons. However, the data rates for the quantum key exchange in two-dimensional QKD are still low, while transmission distance is limited. On the other hand, it is well known that photons can carry both the spin angular momentum (SAM) and the orbital angular momentum (OAM), associated with the polarization and azimuthal phase of the complex electric field, respectively. Accordingly, we can define the combined-OAM-SAM state of a photon as jl; i, where l and correspond to OAM and SAM indexes, respectively. Since the OAM eigenstates are orthogonal, an arbitrary number of bits per single photon can be transmitted, which could considerably increase the total secure bit rate. To improve secure data rates, we propose two types of protocols, namely, nonentangled-based (such as weak coherent state) and entanglement-assisted protocols, both employing the photon combined-OAM-SAM state, which can be used for secure key distribution over free-space optical and few-mode fiber channels. Two types of entanglement-assisted protocols are described, namely, two-basis and ðD þ 1Þ-basis protocols (D is dimensionality of corresponding Hilbert space). We further describe how to implement the qudit gates required for implementation of these protocols. Finally, we discuss the security issues of the proposed protocols and determine both infinite and finite secret key fraction rates.Index Terms: Quantum information processing (QIP), quantum qudit gates, quantum key distribution (QKD), orbital angular momentum (OAM), spin angular momentum (SAM), low-density parity-check (LDPC) codes.

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Section: Multidimensional Qkd Over Few-mode Fiber and Free-space Optimentioning

confidence: 97%

Multidimensional QKD Based on Combined Orbital and Spin Angular Momenta of Photon

Djordjević

2013

IEEE Photonics J.

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“…Because photons can carry both spin angular momentum (SAM), associated with polarization (σ ħ= ± ħ, for circular polarization) and orbital angular momentum (OAM) l ħ (l = 0, ±1,±2,…, ±L, …), associated with azimuthal phase of the complex electric field exp(-jlφ) [1]- [5], it is possible to exploit non-orthogonal photon angular momentum states, defined over computational basis states |l,σ, for multidimensional QKD (MQKD). By limiting OAM index l to maximum L, the corresponding space is D = 2(2L + 1)-dimensional.…”

Section: Entanglement Assisted Photon Angular Momentum-based Multidimmentioning

confidence: 99%

“…It has been widely recognized that the underlying principles of quantum mechanics can be used to enable secure communications, while utilizing the properties of the photons [1]- [5]. Considerable research efforts have been invested to develop an efficient quantum key distribution (QKD) scheme over either free-space optical or fiberoptics channels.…”

Section: Introductionmentioning

confidence: 99%

Photon angular momentum based multidimensional quantum key distribution

Djordjević

Zhang

2014

2014 16th International Conference on Transparent Optical Networks (ICTON)

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In this invited paper, we describe the photon angular momentum based entanglement assisted quantum key distribution (QKD) protocols, analyse their security, and determine the secure finite key fraction rates. Two types of entanglement-assisted protocols, namely two-basis and (D+1)-basis protocols (D is dimensionality of corresponding Hilbert space), have been identified as the most promising. We further analyse the implementation of the qubit gates required for these protocols. We demonstrate that photon angular momentum based QKD protocols significantly outperform corresponding two-dimensional QKD protocols in terms of the finite secret key rates.

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“…Therefore broadband X-waves are minimal X-waves capable to carry a given amount of OAM. Being diffraction-free, dispersion-free, and minimal OAM carriers (and other properties such as self-healing behavior and turbulence resistance [22]), broadband X-waves appear as optimum waves modes in many applications, particularly in superdense, multichannel free-space communications [23], and free-space quantum communications systems [24,25], commonly based on Laguerre-Gauss-type modes.…”

Section: Introductionmentioning

confidence: 99%

Broadband X-waves with orbital angular momentum

Porras,

García-Álvarez

2021

Preprint

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We describe the minimal diffraction-free and dispersion-free, superluminal wave packets (X-waves and generic superluminal localized waves) that can carry a given amount of units m of orbital angular momentum (OAM) per photon. Even if their frequency spectrum is wide enough to synthesize a unipolar pulse, OAM imposes a temporal pulse shape with as many zeroes as units of OAM, and therefore |m|/2 temporal oscillations. All the frequencies in the broadband spectrum are displayed, like in a rainbow, from the bluer ones in the vicinity of the vortex to the redder ones in the wave periphery. At the same time, the whole wave paclet experiences a blue shift proportional to |m|. As a result of the radial red shift and the OAM blue shift, the colour of the brilliant ring around the central vortex is independent of OAM, and solely determined by the broadband source spectrum. Given the very peculiar properties of X-waves with OAM, their generation and use, instead of standard Laguerre-Gauss modes, could improve the performance of OAM-based communication and quantum cryptographic systems, as well as the efficiency of the generation of high harmonics and attosecond pulses with OAM.

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On the quantum-channel capacity for orbital angular momentum-based free-space optical communications

Cited by 28 publications

References 8 publications

Multidimensional QKD Based on Combined Orbital and Spin Angular Momenta of Photon

Multidimensional QKD Based on Combined Orbital and Spin Angular Momenta of Photon

Photon angular momentum based multidimensional quantum key distribution

Broadband X-waves with orbital angular momentum

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