Spatial correlations in parametric down-conversion

Walborn, S. P.; Monken, C. H.; Pádua, S.; Ribeiro, P. H. Souto

doi:10.1016/j.physrep.2010.06.003

Cited by 363 publications

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“…Within the monochromatic and paraxial approximations, the spatial state of the photon pair at the near-field of the BBO source can be written as [35] |ψ (2) …”

Section: Appendix I: Spatial Entanglement From Spdcmentioning

confidence: 99%

“…In usual conditions, the state (9) can display a large amount of entanglement, which appears in the form of spatial correlations of the photons in the near-field, and anti-correlations in the far-field [35]. Moreover, these correlations can be observed simultaneously with the polarization correlations [11].…”

Section: Appendix I: Spatial Entanglement From Spdcmentioning

confidence: 99%

mentioning

confidence: 99%

“…1 shows our experimental setup. A 325nm He-Cd laser pumps two BBO crystals (2mm length), producing polarization and spatially entangled photon pairs via colinear spontaneous parametric down-conversion (SPDC) [34,35] with degenerate wavelength 650 nm. The state of the twin photons is well-described by |Ψ (2) = |Φ + ⊗ |ψ (2) , where |ψ (2) stands for the spatial degrees of freedom of the photon pair, and |Φ + = (|HH + |V V )/ √ 2 is the polarization state, with H (V ) standing for horizontal (vertical) polarization.…”

mentioning

confidence: 99%

“…The state of the twin photons is well-described by |Ψ (2) = |Φ + ⊗ |ψ (2) , where |ψ (2) stands for the spatial degrees of freedom of the photon pair, and |Φ + = (|HH + |V V )/ √ 2 is the polarization state, with H (V ) standing for horizontal (vertical) polarization. In usual conditions, photons pairs from SPDC display a large amount of spatial entanglement, which appears in the form of correlations of the photons in the near-field, and anti-correlations in the far-field [35] (see Appendix I). A pair of lenses (not shown) is used to map the source plane onto mirror M2.…”

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confidence: 99%

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Quantum-enhanced sensing from hyperentanglement

Walborn

Filho

2018

Phys. Rev. A

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Hyperentanglement -simultaneous entanglement between multiple degrees of freedom of two or more systems -has been used to enhance quantum information tasks such as quantum communication and photonic quantum computing. Here we show that hyperentanglement can lead to increased quantum advantage in metrology, with contributions from the entanglement in each degree of freedom, allowing for Heisenberg scaling in the precision of parameter estimation. Our experiment employs photon pairs entangled in polarization and spatial degrees of freedom to estimate a small tilt angle of a mirror. Precision limits beyond shot noise are saturated through a simple binary measurement of the polarization state. The broad validity of the dynamics considered here implies that similar strategies based on hyperentanglement can offer improvement in a wide variety of metrological tasks.To exploit the advantage of quantum entanglement for tasks such as computation and metrology requires producing highdimensional quantum states composed of many entangled sub-systems [1][2][3][4]. In addition to the difficulty in producing large entangled states, they are typically very sensitive to noise [5][6][7]. An alternative route to enhance the size of a system is through hyperentanglement [8], that is, the entanglement in multiple degrees of freedom (DOF) of a composite quantum system. So far, hyperentanglement has found use in high-capacity quantum communication [9][10][11][12][13], photonic quantum computing [14,15], tests of quantum non-locality [16,17], and the direct characterization of entanglement [18] and quantum dynamics [19]. Here we demonstrate the usefulness of hyperentanglement in metrology, allowing one to reach the ultimate quantum precision limits, for the paradigmatic case of an interaction between two degrees of freedom of the same system. Examples of this type of evolution include the interaction between spin and momentum in a SternGerlach experiment, between internal and external DOF of trapped ions [20], or the polarization and spatial DOF of an optical field propagating through a birefringent medium [21].Our experiment employs hyperentangled photon pairs to monitor a tiny rotation of a mirror. Entanglement in both spatial and polarization DOF leads to increased quantum advantage in metrological sensing, allowing for Heisenberg scaling in the number of photons N used to probe the rotation: the precision of estimation becomes proportional to 1/N , instead of the shot-noise behavior ∝ 1/ √ N . Estimation of tilt angles of mirrors is important in several fields of science [22][23][24][25]. A common procedure consists in detecting the spatial or phase displacement of a laser beam reflected by the mirror [26][27][28][29][30][31][32]. Our method, on the other hand, is based solely on a binary polarization measurement at the output of an interferometer with a displaced input beam. This scheme takes advantage of both hyper-entanglement and beam displacement to increase the precision beyond the shot-noise limit.Precision measurements and F...

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“…Within the monochromatic and paraxial approximations, the spatial state of the photon pair at the near-field of the BBO source can be written as [35] |ψ (2) …”

Section: Appendix I: Spatial Entanglement From Spdcmentioning

confidence: 99%

Section: Appendix I: Spatial Entanglement From Spdcmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Quantum-enhanced sensing from hyperentanglement

Walborn

Filho

2018

Phys. Rev. A

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Materials Innovations for Quantum Technology Acceleration: A Perspective

et al. 2023

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A broad perspective of quantum technology state of the art is provided and critical stumbling blocks for quantum technology development are identified. Innovations in demonstrating and understanding electron entanglement phenomena using bulk and low‐dimensional materials and structures are summarized. Correlated photon‐pair generation via processes such as nonlinear optics is discussed. Application of qubits to current and future high‐impact quantum technology development is presented. Approaches for realizing unique qubit features for large‐scale encrypted communication, sensing, computing, and other technologies are still evolving; thus, materials innovation is crucially important. A perspective on materials modeling approaches for quantum technology acceleration that incorporate physics‐based AI/ML, integrated with quantum metrology is discussed.

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Perspectives for Applications of Quantum Imaging

Basset

Setzpfandt

Steinlechner

et al. 2019

Laser & Photonics Reviews

127

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Quantum imaging is a multifaceted field of research that promises highly efficient imaging in extreme spectral ranges as well as ultralow‐light microscopy. Since the first proof‐of‐concept experiments over 30 years ago, the field has evolved from highly fascinating academic research to the verge of demonstrating practical technological enhancements in imaging and microscopy. Here, the aim is to give researchers from outside the quantum optical community, in particular those applying imaging technology, an overview of several promising quantum imaging approaches and evaluate both the quantum benefit and the prospects for practical usage in the near future. Several use case scenarios are discussed and a careful analysis of related technology requirements and necessary developments toward practical and commercial application is provided.

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Spatial correlations in parametric down-conversion

Cited by 363 publications

References 297 publications

Quantum-enhanced sensing from hyperentanglement

Quantum-enhanced sensing from hyperentanglement

Materials Innovations for Quantum Technology Acceleration: A Perspective

Perspectives for Applications of Quantum Imaging

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