Quantum Emulation of Gravitational Waves

Gravitational waves, as predicted by Einstein's general relativity theory, appear as ripples in the fabric of spacetime traveling at the speed of light. We prove that the propagation of small amplitude gravitational waves in a curved spacetime is equivalent to the propagation of a subspace of electromagnetic states. We use this result to propose the use of entangled photons to emulate the evolution of gravitational waves in curved spacetimes by means of experimental electromagnetic setups featuring metamaterials.Comment: 10 pages, 2 figure

Symmetry Protection of Photonic Entanglement in the Interaction with a Single Nanoaperture

In this work, we experimentally show that quantum entanglement can be symmetry protected in the interaction with a single subwavelength plasmonic nanoaperture, with a total volume of V ∼ 0.2λ^3. In particular, we experimentally demonstrate that two-photon entanglement can be either completely preserved or completely lost after the interaction with the nanoaperture, solely depending on the relative phase between the quantum states. We achieve this effect by using specially engineered two-photon states to match the properties of the nanoaperture. In this way we can access a symmetry protected state, i.e., a state constrained by the geometry of the interaction to retain its entanglement. In spite of the small volume of interaction, we show that the symmetry protected entangled state retains its main properties. This connection between nanophotonics and quantum optics probes the fundamental limits of the phenomenon of quantum interference

Quantum interference through plasmonic nanostructures

Empirical thesis.Bibliography: pages 79-90.1. General introduction -- 2. Technical introduction -- 3. Controlling the SPDC wave function -- 4. Measuring the SPDC wave function -- 5. Two-photon interactions with nanoapertures -- 6. Conclusion -- Appendices -- References.Quantum technologies like quantum computing, quantum communication or quantum metrology promise astonishing advantages over their classical counterparts. However, they all require excellent control and protection of the involved quantum states. In this respect, photons are ideal carriers of quantum information due to their robustness against decoherence and the ease with which they can be transferred over long distances. At the same time they suffer from weak interactions with matter and the large structures necessary, as given by the wavelength of light. Combining quantum optics with plasmonic structures could open an avenue to address these drawbacks while still benefiting from the advantages of photons.We present for the first time the transmission of an entangled two-photon state through a plasmonic aperture that is smaller than the wavelength of the light. Entanglement is the key resource for many quantum information schemes and its protection of great interest. Strong interactions with the nanoaperture usually destroy the entanglement of an arbitrary state. We tailor a special state for the interaction – taking into account the specific properties of the aperture – that leads to quantum interference and eventually protects the entanglement from degradation. We experimentally demonstrate creation of this state, transmission through the nanoaperture and successful protection of the entanglement.On our way to this achievement, we improve our control over the spontaneous parametric down-conversion source of photon pairs. We report a surprising dependence of the time delay distribution between the photons of the pair on the position of the non-linear crystal. We experimentally confirm the effect via quantum interference experiments and challenging direct measurements of the arrival time. Furthermore, a novel reconstruction scheme for the complex spectral biphoton wave function allows us to study the temporal correlations in more detail and to shape the wave function. We experimentally demonstrate the reconstruction in different situations and find an unexpected temporal distribution with a detection mode carrying orbital angular momentum.Mode of access: World wide web1 online resource (xiv, 91 pages) illustrations (some colour

Manipulating the temporal correlations of two-photon states through the spatial degree of freedom

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