Quantum Correlations in Optical Angle–Orbital Angular Momentum Variables

Abstract

Entanglement of the properties of two separated particles constitutes a fundamental signature of quantum mechanics and is a key resource for quantum information science. We demonstrate strong Einstein, Podolsky, and Rosen correlations between the angular position and orbital angular momentum of two photons created by the nonlinear optical process of spontaneous parametric down-conversion. The discrete nature of orbital angular momentum and the continuous but periodic nature of angular position give rise to a special sort of entanglement between these two variables. The resulting correlations are found to be an order of magnitude stronger than those allowed by the uncertainty principle for independent (nonentangled) particles. Our results suggest that angular position and orbital angular momentum may find important applications in quantum information science.

Increasing the dimension in high-dimensional two-photon orbital angular momentum entanglement

“…More relevant to practical applications, higher-dimensional entanglement provides higher information capacity [7,8] and increased security and robustness [8,9]. Experimentally, D-levels in photons can be achieved by using the temporal and spectral degrees of freedom [10], polarisation of more than one photon [11], transverse spatial profile [7], position and linear momentum [12], and angular position and orbital angular momentum [13].The entanglement of orbital angular momentum (OAM) in photons generated via spontaneous parametric down-conversion (SPDC) is firmly established theoretically and experimentally [14,15]. The interest in OAM stems from its discrete and theoretically infinitedimensional Hilbert space.…”

Hybrid entanglement swapping of photons: Creating the orbital angular momentum Bell states and Greenberger-Horne-Zeilinger states

“…The strong EPR correlations in angle-orbital angular momentum variables were very recently demonstrated, which creates a new opportunity for increasing bandwidth in quantum cryptography [18]. As an ideal candidate to represent higher-dimensional quantum al-phabet, OAM has been employed to test local realism with the violation of a two-photon, three-dimensional Bell inequality [19] and OAM-based quantum cryptographic scheme for key distribution has been reported [20].…”

Massive individual orbital angular momentum channels for multiplexing enabled by Dammann gratings

“…The superior security advantages of OAM channels have also been demonstrated in both classical and quantum communication systems. [14][15][16][17][18][19] OAM-based optical communications can be classified into two different categories: OAM shift keying (OAM-SK) and OAM division multiplexing (OAM-DM). For OAM-SK, the OAM states of the OV beams are regarded as a modulation format that enables the encoding of information by dynamic switching of spatial light modulators.…”