Cauchy–Schwarz inequality for general measurements as an entanglement criterion

Wasak, Tomasz; Szańkowski, Piotr; Trippenbach, Marek; Chwedeńczuk, Jan

doi:10.1007/s11128-015-1181-z

Cited by 8 publications

(5 citation statements)

References 48 publications

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“…4B . The CSI can be violated for quantum states, when Γ( q s ) < C (0), indicating nonclassical spatial correlations and multimode spatial entanglement ( 46 ). The underlying physics can be interpreted as the spatial analog of the photon antibunching effect ( 47 ).…”

Section: Resultsmentioning

confidence: 99%

Spatially entangled photon pairs from lithium niobate nonlocal metasurfaces

Zhang

Parry

et al. 2022

Sci. Adv.

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Metasurfaces consisting of nanoscale structures are underpinning new physical principles for the creation and shaping of quantum states of light. Multiphoton states that are entangled in spatial or angular domains are an essential resource for many quantum applications; however, their production traditionally relies on bulky nonlinear crystals. We predict and demonstrate experimentally the generation of spatially entangled photon pairs through spontaneous parametric down-conversion from a metasurface incorporating a nonlinear thin film of lithium niobate covered by a silica meta-grating. We measure the correlations of photon pairs and identify their spatial antibunching through violation of the classical Cauchy-Schwarz inequality, witnessing the presence of multimode entanglement. Simultaneously, the photon-pair rate is strongly enhanced by 450 times as compared to unpatterned films because of high-quality-factor resonances. These results pave the way to miniaturization of various quantum devices by incorporating ultrathin metasurfaces functioning as room temperature sources of quantum-entangled photons.

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Section: Resultsmentioning

confidence: 99%

Spatially entangled photon pairs from lithium niobate nonlocal metasurfaces

Zhang

Parry

et al. 2022

Sci. Adv.

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“…The CSI can be violated for quantum states, when Γ(q s ) < C(0), indicating non-classical spatial correlations and multi-mode spatial entanglement [41]. The underlying physics can be interpreted as the spatial analogue of the photon antibunching effect [42].…”

Section: Concept and Modellingmentioning

confidence: 99%

Spatially entangled photon-pairs from lithium niobate nonlocal metasurfaces

Zhang,

Ma,

Parry

et al. 2022

Preprint

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Metasurfaces consisting of nano-scale structures are underpinning new physical principles for the creation and shaping of quantum states of light.Multi-photon states that are entangled in spatial or angular domains are an essential resource for quantum imaging and sensing applications, however their production traditionally relies on bulky nonlinear crystals. We predict and demonstrate experimentally the generation of spatially entangled photon pairs through spontaneous parametric down-conversion from a metasurface incorporating a nonlinear thin film of lithium niobate. This is achieved through nonlocal resonances with tailored angular dispersion mediated by an integrated silica meta-grating, enabling control of the emission pattern and associated quantum states of photon pairs by designing the grating profile and tuning the pump frequency. We measure the correlations of photon positions and identify their spatial anti-bunching through violation of the classical Cauchy-Schwartz inequality, witnessing the presence of multi-mode entanglement. Simultaneously, the photon-pair rate is strongly enhanced by 450 times as compared to unpatterned films due to high-quality-factor metasurface resonances, and the coincidence to accidental ratio reaches 5000. These results pave the way to miniaturization of various quantum devices by incorporating ultra-thin metasurfaces functioning as room-temperature sources of quantum-entangled photons.

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“…where P is a probability distribution of the variables (z, ϕ). The expression (10) is the fixed-N analog of the classical state of the electromagnetic field, according to the Glauber-Sudarshan criterion [42][43][44][45]. The expressions (9) and (10) can be easily generalized to the multimode setup.…”

Section: Role Of the Particle Entanglementmentioning

confidence: 99%

Quantum interferometry in multimode systems

Chwedeńczuk

2017

Phys. Rev. A

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We consider the situation when the signal propagating through each arm of an interferometer has a complicated multi-mode structure. We find the relation between the particle-entanglement and the possibility to surpass the shot-noise limit of the phase estimation. Our results are generalthey apply to pure and mixed states of identical and distinguishable particles (or combinations of both), for a fixed and fluctuating number of particles. We also show that the method for detecting the entanglement often used in two-mode system can give misleading results when applied to the multi-mode case.

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Cauchy–Schwarz inequality for general measurements as an entanglement criterion

Cited by 8 publications

References 48 publications

Spatially entangled photon pairs from lithium niobate nonlocal metasurfaces

Spatially entangled photon pairs from lithium niobate nonlocal metasurfaces

Spatially entangled photon-pairs from lithium niobate nonlocal metasurfaces

Quantum interferometry in multimode systems

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