151
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Jha AK, Malik M, Boyd RW. Exploring energy-time entanglement using geometric phase. PHYSICAL REVIEW LETTERS 2008; 101:180405. [PMID: 18999801 DOI: 10.1103/physrevlett.101.180405] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2008] [Indexed: 05/27/2023]
Abstract
Using the signal and idler photons produced by parametric down-conversion, we report an experimental observation of a violation of the Bell inequality for energy and time based purely on the geometric phases of the signal and idler photons. We thus show that energy-time entanglement between the signal and idler photons can be explored by means of their geometric phases. These results may have important practical implications for quantum information science by providing an additional means by which entanglement can be manipulated.
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Affiliation(s)
- Anand Kumar Jha
- The Institute of Optics, University of Rochester, Rochester, New York 14627, USA
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152
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Avenhaus M, Coldenstrodt-Ronge HB, Laiho K, Mauerer W, Walmsley IA, Silberhorn C. Photon number statistics of multimode parametric down-conversion. PHYSICAL REVIEW LETTERS 2008; 101:053601. [PMID: 18764391 DOI: 10.1103/physrevlett.101.053601] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2008] [Indexed: 05/26/2023]
Abstract
We experimentally analyze the complete photon number statistics of parametric down-conversion and ascertain the influence of multimode effects. Our results clearly reveal a difference between single-mode theoretical description and the measured distributions. Further investigations assure the applicability of loss-tolerant photon number reconstruction and prove strict photon number correlation between signal and idler modes.
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Affiliation(s)
- M Avenhaus
- Max-Planck Research Group, Günther-Scharowsky-Strasse 1/Bau 24, Erlangen, Germany.
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153
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Kawase D, Miyamoto Y, Takeda M, Sasaki K, Takeuchi S. Observing quantum correlation of photons in Laguerre-Gauss modes using the Gouy phase. PHYSICAL REVIEW LETTERS 2008; 101:050501. [PMID: 18764380 DOI: 10.1103/physrevlett.101.050501] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2008] [Indexed: 05/26/2023]
Abstract
The effect of the Gouy phase, which is one of the geometrical phases of photons, is observed through quantum correlation in Laguerre-Gaussian (LG) modes. In an experiment, the relative phase of two different LG modes of measurement basis states is manipulated via the Gouy phase, and the observed coincidence count rates agree well with theoretical predictions. This result suggests that the Gouy phase can be used as a new tool to manipulate multidimensional photonic quantum states.
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Affiliation(s)
- Daisuke Kawase
- Research Institute for Electronic Science, Hokkaido University, Sapporo, Japan
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154
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Yarnall T, Abouraddy AF, Saleh BEA, Teich MC. Spatial coherence effects on second- and fourth-order temporal interference. OPTICS EXPRESS 2008; 16:7634-7640. [PMID: 18545470 DOI: 10.1364/oe.16.007634] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
We report the results of two experiments performed with two-photon light, produced via collinear degenerate optical spontaneous parametric downconversion (SPDC), in which both second-order (one-photon) and fourth-order (two-photon) interferograms are recorded in a Mach-Zehnder interferometer (MZI). In the first experiment, high-visibility fringes are obtained for both the second- and fourth-order interferograms. In the second experiment, the MZI is modified by the removal of a mirror from one of its arms; this leaves the fourth-order interferogram unchanged, but extinguishes the second-order interferogram. A theoretical model that takes into consideration both the temporal and spatial degrees-of-freedom of the two-photon state successfully explains the results. While the temporal interference in the MZI is independent of the spatial coherence of the source, that of the modified MZI is not.
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Affiliation(s)
- Timothy Yarnall
- Lincoln Laboratory, Massachusetts Institute of Technology, 244 Wood Street, Lexington, Massachusetts 02420-9108, USA
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155
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Yarnall T, Abouraddy AF, Saleh BEA, Teich MC. Synthesis and analysis of entangled photonic qubits in spatial-parity space. PHYSICAL REVIEW LETTERS 2007; 99:250502. [PMID: 18233506 DOI: 10.1103/physrevlett.99.250502] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2007] [Revised: 06/26/2007] [Indexed: 05/25/2023]
Abstract
We present the novel embodiment of a photonic qubit that makes use of one continuous spatial degree of freedom of a single photon and relies on the parity of the photon's transverse spatial distribution. Using optical spontaneous parametric down-conversion to produce photon pairs, we demonstrate the controlled generation of entangled-photon states in this new space. Specifically, two Bell states, and a continuum of their superpositions, are generated by simple manipulation of a classical parameter, the optical-pump spatial parity, and not by manipulation of the entangled photons themselves. An interferometric device, isomorphic in action to a polarizing beam splitter, projects the spatial-parity states onto an even-odd basis. This new physical realization of photonic qubits could be used as a foundation for future experiments in quantum information processing.
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Affiliation(s)
- Timothy Yarnall
- Quantum Imaging Laboratory, Departments of Electrical & Computer Engineering and Physics, Boston University, Boston, Massachusetts 02215-2421, USA
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156
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Cabello A, Moreno P. Bipartite all-versus-nothing proofs of Bell's theorem with single-qubit measurements. PHYSICAL REVIEW LETTERS 2007; 99:220402. [PMID: 18233265 DOI: 10.1103/physrevlett.99.220402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2007] [Indexed: 05/25/2023]
Abstract
If n qubits were distributed between 2 parties, which quantum pure states and distributions of qubits would allow all-versus-nothing (or Greenberger-Horne-Zeilinger-like) proofs of Bell's theorem using only single-qubit measurements? We show a necessary and sufficient condition for the existence of these proofs for any number of qubits, and provide all distinct proofs up to n=7 qubits. Remarkably, there is only one distribution of a state of n=4 qubits, and six distributions, each for a different state of n=6 qubits, which allow these proofs.
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Affiliation(s)
- Adán Cabello
- Departamento de Física Aplicada II, Universidad de Sevilla, E-41012 Sevilla, Spain.
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157
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Osorio CI, Molina-Terriza G, Font BG, Torres JP. Azimuthal distinguishability of entangled photons generated in spontaneous parametric down-conversion. OPTICS EXPRESS 2007; 15:14636-14643. [PMID: 19550744 DOI: 10.1364/oe.15.014636] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We experimentally demonstrate that paired photons generated in different sections of a down-conversion cone, when some of the interacting waves show Poynting vector walk-off, carry different spatial correlations, and therefore a different degree of spatial entanglement. This is shown to be in agreement with theoretical results. We also discuss how this azimuthal distinguishing information of the down-conversion cone is relevant for the implementation of quantum sources aimed at the generation of entanglement in other degrees of freedom, such as polarization.
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158
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Chen K, Li CM, Zhang Q, Chen YA, Goebel A, Chen S, Mair A, Pan JW. Experimental realization of one-way quantum computing with two-photon four-qubit cluster states. PHYSICAL REVIEW LETTERS 2007; 99:120503. [PMID: 17930486 DOI: 10.1103/physrevlett.99.120503] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2007] [Indexed: 05/25/2023]
Abstract
We report an experimental realization of one-way quantum computing on a two-photon four-qubit cluster state. This is accomplished by developing a two-photon cluster state source entangled both in polarization and spatial modes. With this special source, we implemented a highly efficient Grover's search algorithm and high-fidelity two-qubit quantum gates. Our experiment demonstrates that such cluster states could serve as an ideal source and a building block for rapid and precise optical quantum computation.
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Affiliation(s)
- Kai Chen
- Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, Philosophenweg 12, 69120 Heidelberg, Germany
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159
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Abstract
When light is transmitted through optically inhomogeneous and anisotropic media the spatial distribution of light can be modified according to its input polarization state. A complete analysis of this process, based on the paraxial approximation, is presented, and we show how it can be exploited to produce a spin-controlled change in the orbital angular momentum of light beams propagating in patterned space-variant optical axis phase plates. We also unveil a new effect: the development of a strong modulation in the angular momentum change upon variation of the optical path through the phase plates.
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Affiliation(s)
- Gabriel F Calvo
- Grup de Física Teòrica, Universitat Autònoma de Barcelona, Bellaterna, Barcelona, Spain
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160
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Aolita L, Walborn SP. Quantum communication without alignment using multiple-qubit single-photon states. PHYSICAL REVIEW LETTERS 2007; 98:100501. [PMID: 17358518 DOI: 10.1103/physrevlett.98.100501] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2006] [Indexed: 05/14/2023]
Abstract
We propose a scheme for encoding logical qubits in a subspace protected against collective rotations around the propagation axis using the polarization and transverse spatial degrees of freedom of single photons. This encoding allows for quantum key distribution without the need of a shared reference frame. We present methods to generate entangled states of two logical qubits using present day down-conversion sources and linear optics, and show that the application of these entangled logical states to quantum information schemes allows for alignment-free tests of Bell's inequalities, quantum dense coding, and quantum teleportation.
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Affiliation(s)
- L Aolita
- Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, Rio de Janeiro, RJ 21941-972, Brazil
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161
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Ali-Khan I, Broadbent CJ, Howell JC. Large-alphabet quantum key distribution using energy-time entangled bipartite States. PHYSICAL REVIEW LETTERS 2007; 98:060503. [PMID: 17358925 DOI: 10.1103/physrevlett.98.060503] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2006] [Revised: 11/27/2006] [Indexed: 05/14/2023]
Abstract
We present a protocol for large-alphabet quantum key distribution (QKD) using energy-time entangled biphotons. Binned, high-resolution timing measurements are used to generate a large-alphabet key with over 10 bits of information per photon pair, albeit with large noise. QKD with 5% bit error rate is demonstrated with 4 bits of information per photon pair, where the security of the quantum channel is determined by the visibility of Franson interference fringes. The protocol is easily generalizable to even larger alphabets, and utilizes energy-time entanglement which is robust to transmission over large distances in fiber.
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Affiliation(s)
- Irfan Ali-Khan
- Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA
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162
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Barbieri M, De Martini F, Mataloni P, Vallone G, Cabello A. Enhancing the violation of the einstein-podolsky-rosen local realism by quantum hyperentanglement. PHYSICAL REVIEW LETTERS 2006; 97:140407. [PMID: 17155228 DOI: 10.1103/physrevlett.97.140407] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2006] [Indexed: 05/12/2023]
Abstract
Mermin's observation [Phys. Rev. Lett. 65, 1838 (1990)] that the magnitude of the violation of local realism, defined as the ratio between the quantum prediction and the classical bound, can grow exponentially with the size of the system is demonstrated using two-photon hyperentangled states entangled in polarization and path degrees of freedom, and local measurements of polarization and path simultaneously.
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Affiliation(s)
- Marco Barbieri
- Dipartimento di Fisica dell'Università La Sapienza and Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia, 00185 Roma, Italy
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163
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Cabello A. Bipartite bell inequalities for hyperentangled states. PHYSICAL REVIEW LETTERS 2006; 97:140406. [PMID: 17155227 DOI: 10.1103/physrevlett.97.140406] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2006] [Indexed: 05/12/2023]
Abstract
We show that bipartite Bell inequalities based on the Einstein-Podolsky-Rosen criterion for elements of reality and derived from the properties of some hyperentangled states allow feasible experimental verification of the fact that quantum nonlocality grows exponentially with the size of the subsystems, and Bell loophole-free tests with currently available photodetection efficiencies.
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Affiliation(s)
- Adán Cabello
- Departamento de Física Aplicada II, Universidad de Sevilla, 41012 Sevilla, Spain.
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164
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Aolita L, Mintert F. Measuring multipartite concurrence with a single factorizable observable. PHYSICAL REVIEW LETTERS 2006; 97:050501. [PMID: 17026084 DOI: 10.1103/physrevlett.97.050501] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2006] [Indexed: 05/12/2023]
Abstract
We show that, for any composite system with an arbitrary number of finite-dimensional subsystems, it is possible to directly measure the multipartite concurrence of pure states by detecting only one single factorizable observable, provided that two copies of the composite state are available. This result can be immediately put into practice in trapped-ion and entangled-photon experiments.
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Affiliation(s)
- Leandro Aolita
- Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, 21941-972 Rio de Janeiro, RJ, Brazil.
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