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Author |
Tassin, Philippe; Koschny, Thomas; Kafesaki, Maria; Soukoulis, Costas M. |
Title |
A comparison of graphene, superconductors and metals as conductors for metamaterials and plasmonics |
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Journal Article |
Year |
2012 |
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Nature Photonics |
Abbreviated Journal |
Nat. Photon. |
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6 |
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4 |
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259-264 |
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fromIPMRAS |
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Recent advancements in metamaterials and plasmonics have promised a number of exciting applications, in particular at terahertz and optical frequencies. Unfortunately, the noble metals used in these photonic structures are not particularly good conductors at high frequencies, resulting in significant dissipative loss. Here, we address the question of what is a good conductor for metamaterials and plasmonics. For resonant metamaterials, we develop a figure-of-merit for conductors that allows for a straightforward classification of conducting materials according to the resulting dissipative loss in the metamaterial. Application of our method predicts that graphene and high-Tc superconductors are not viable alternatives for metals in metamaterials. We also provide an overview of a number of transition metals, alkali metals and transparent conducting oxides. For plasmonic systems, we predict that graphene and high-Tc superconductors cannot outperform gold as a platform for surface plasmon polaritons, because graphene has a smaller propagation length-to-wavelength ratio. |
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RPLAB @ gujma @ |
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790 |
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Goulielmakis, Eleftherios |
Title |
Attosecond photonics: Extreme ultraviolet catastrophes |
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Journal Article |
Year |
2012 |
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Nature Photonics |
Abbreviated Journal |
Nat. Photon. |
Volume |
6 |
Issue |
3 |
Pages |
142-143 |
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fromIPMRAS |
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Extreme ultraviolet attosecond pulses, which emerge from the interaction of atoms with intense laser fields, play a central role in modern ultrafast science and the exploration of electron behaviour. Recent work now shows that catastrophe theory can help optimize the properties of these pulses. |
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RPLAB @ gujma @ |
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791 |
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Usmani, Imam; Clausen, Christoph; Bussières, Félix; Sangouard, Nicolas; Afzelius, Mikael; Gisin, Nicolas |
Title |
Heralded quantum entanglement between two crystals |
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Journal Article |
Year |
2012 |
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Nature Photonics |
Abbreviated Journal |
Nat. Photon. |
Volume |
6 |
Issue |
4 |
Pages |
234-237 |
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fromIPMRAS |
Abstract |
Quantum networks must have the crucial ability to entangle quantum nodes. A prominent example is the quantum repeater, which allows the distance barrier of direct transmission of single photons to be overcome, provided remote quantum memories can be entangled in a heralded fashion. Here, we report the observation of heralded entanglement between two ensembles of rare-earth ions doped into separate crystals. A heralded single photon is sent through a 50/50 beamsplitter, creating a single-photon entangled state delocalized between two spatial modes. The quantum state of each mode is subsequently mapped onto a crystal, leading to an entangled state consisting of a single collective excitation delocalized between two crystals. This entanglement is revealed by mapping it back to optical modes and by estimating the concurrence of the retrieved light state. Our results highlight the potential of crystals doped with rare-earth ions for entangled quantum nodes and bring quantum networks based on solid-state resources one step closer. |
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RPLAB @ gujma @ |
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793 |
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Hase, Muneaki; Katsuragawa, Masayuki; Constantinescu, Anca Monia; Petek, Hrvoje |
Title |
Frequency comb generation at terahertz frequencies by coherent phonon excitation in silicon |
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Journal Article |
Year |
2012 |
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Nature Photonics |
Abbreviated Journal |
Nat. Photon. |
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6 |
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243–247 |
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fromIPMRAS |
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High-order nonlinear light–matter interactions in gases enable the generation of X-ray and attosecond light pulses, metrology and spectroscopy1. Optical nonlinearities in solid-state materials are particularly interesting for combining optical and electronic functions for high-bandwidth information processing2. Third-order nonlinear optical processes in silicon have been used to process optical signals with bandwidths greater than 1 GHz (ref. 2). However, fundamental physical processes for a silicon-based optical modulator in the terahertz bandwidth range have not yet been explored. Here, we demonstrate ultrafast phononic modulation of the optical index of silicon by irradiation with intense few-cycle femtosecond pulses. The anisotropic reflectivity modulation by the resonant Raman susceptibility at the fundamental frequency of the longitudinal optical phonon of silicon (15.6 THz) generates a frequency comb up to seventh order. All-optical >100 THz frequency comb generation is realized by harnessing the coherent atomic motion of the silicon crystalline lattice at its highest mechanical frequency. |
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RPLAB @ gujma @ |
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794 |
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Author |
Mineev, Vladimir P. |
Title |
Superfluid helium: Order in disorder |
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Journal Article |
Year |
2012 |
Publication |
Nature Physics |
Abbreviated Journal |
Nat. Phys. |
Volume |
8 |
Issue |
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Pages |
253–254 |
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fromIPMRAS |
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Confining liquid 3He in porous silica aerogel prepared with strong anisotropy stabilizes a state of axial superfluidity. |
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RPLAB @ gujma @ |
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810 |
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Author |
Clerk, Aashish |
Title |
Quantum phononics: To see a SAW |
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Journal Article |
Year |
2012 |
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Nature Physics |
Abbreviated Journal |
Nat. Phys. |
Volume |
8 |
Issue |
4 |
Pages |
256-257 |
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fromIPMRAS |
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Mechanical oscillations of microscopic resonators have recently been observed in the quantum regime. This idea could soon be extended from localized vibrations to travelling waves thanks to a sensitive probe of so-called surface acoustic waves. |
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RPLAB @ gujma @ |
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811 |
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Author |
Hollenberg, Lloyd C. L. |
Title |
Quantum control: Through the quantum chicane |
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Journal Article |
Year |
2012 |
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Nature Physics |
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Nat. Phys. |
Volume |
8 |
Issue |
2 |
Pages |
113-114 |
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fromIPMRAS |
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In quantum control there is an inherent tension between high fidelity requirements and the need for speed to avoid decoherence. A direct comparison of quantum control protocols at these two extremes indicates where the sweet spot may lie. |
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812 |
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Gustafsson, Martin V.; Santos, Paulo V.; Johansson, Göran; Delsing, Per |
Title |
Local probing of propagating acoustic waves in a gigahertz echo chamber |
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Journal Article |
Year |
2012 |
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Nature Physics |
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Nat. Phys. |
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8 |
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4 |
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338-343 |
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Abstract |
In the same way that micro-mechanical resonators resemble guitar strings and drums, surface acoustic waves resemble the sound these instruments produce, but moving over a solid surface rather than through air. In contrast with oscillations in suspended resonators, such propagating mechanical waves have not before been studied near the quantum mechanical limits. Here, we demonstrate local probing of surface acoustic waves with a displacement sensitivity of 30amRMSHz-1/2 and detection sensitivity on the single-phonon level after averaging, at a frequency of 932MHz. Our probe is a piezoelectrically coupled single-electron transistor, which is sufficiently fast, non-destructive and localized to enable us to track pulses echoing back and forth in a long acoustic cavity, self-interfering and ringing the cavity up and down. We project that strong coupling to quantum circuits will enable new experiments, and hybrids using the unique features of surface acoustic waves. Prospects include quantum investigations of phonon-phonon interactions, and acoustic coupling to superconducting qubits for which we present favourable estimates. |
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RPLAB @ gujma @ |
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813 |
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Korotkov, Alexander N. |
Title |
Entanglement preservation: The Sleeping Beauty approach |
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Journal Article |
Year |
2012 |
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Nature Physics |
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Nat. Phys. |
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8 |
Issue |
2 |
Pages |
107-108 |
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Two-qubit entanglement can be preserved by partially measuring the qubits to leave them in a 'lethargic' state. The original state is restored using quantum measurement reversal after the qubits have travelled through a decoherence channel. |
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RPLAB @ gujma @ |
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814 |
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Kim, Yong-Su; Lee, Jong-Chan; Kwon, Osung; Kim, Yoon-Ho |
Title |
Protecting entanglement from decoherence using weak measurement and quantum measurement reversal |
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Journal Article |
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2012 |
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Nature Physics |
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Nat. Phys. |
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8 |
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2 |
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117-120 |
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fromIPMRAS |
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Decoherence, often caused by unavoidable coupling with the environment, leads to degradation of quantum coherence. For a multipartite quantum system, decoherence leads to degradation of entanglement and, in certain cases, entanglement sudden death. Tackling decoherence, thus, is a critical issue faced in quantum information, as entanglement is a vital resource for many quantum information applications including quantum computing, quantum cryptography, quantum teleportation and quantum metrology. Here, we propose and demonstrate a scheme to protect entanglement from decoherence. Our entanglement protection scheme makes use of the quantum measurement itself for actively battling against decoherence and it can effectively circumvent even entanglement sudden death. |
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RPLAB @ gujma @ |
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815 |
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Bason, Mark G.; Viteau, Matthieu; Malossi, Nicola; Huillery, Paul; Arimondo, Ennio; Ciampini, Donatella; Fazio, Rosario; Giovannetti, Vittorio; Mannella, Riccardo; Morsch, Oliver |
Title |
High-fidelity quantum driving |
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Journal Article |
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2012 |
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Nature Physics |
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Nat. Phys. |
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8 |
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2 |
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147-152 |
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Accurately controlling a quantum system is a fundamental requirement in quantum information processing and the coherent manipulation of molecular systems. The ultimate goal in quantum control is to prepare a desired state with the highest fidelity allowed by the available resources and the experimental constraints. Here we experimentally implement two optimal high-fidelity control protocols using a two-level quantum system comprising Bose-Einstein condensates in optical lattices. The first is a short-cut protocol that reaches the maximum quantum-transformation speed compatible with the Heisenberg uncertainty principle. In the opposite limit, we realize the recently proposed transitionless superadiabatic protocols in which the system follows the instantaneous adiabatic ground state nearly perfectly. We demonstrate that superadiabatic protocols are extremely robust against control parameter variations, making them useful for practical applications. |
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816 |
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Peruzzo, Alberto; Laing, Anthony; Politi, Alberto; Rudolph, Terry; O'Brien, Jeremy L. |
Title |
Multimode quantum interference of photons in multiport integrated devices |
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Journal Article |
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2011 |
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Nature Communications |
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Nat. Comm. |
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2 |
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224 |
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6 |
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Photonics is a leading approach in realizing future quantum technologies and recently, optical waveguide circuits on silicon chips have demonstrated high levels of miniaturization and performance. Multimode interference (MMI) devices promise a straightforward implementation of compact and robust multiport circuits. Here, we show quantum interference in a 2×2 MMI coupler with visibility of V=95.6+/-0.9%. We further demonstrate the operation of a 4×4 port MMI device with photon pairs, which exhibits complex quantum interference behaviour. We have developed a new technique to fully characterize such multiport devices, which removes the need for phase-sensitive measurements and may find applications for a wide range of photonic devices. Our results show that MMI devices can operate in the quantum regime with high fidelity and promise substantial simplification and concatenation of photonic quantum circuits. |
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763 |
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Ikuta, Rikizo; Kusaka, Yoshiaki; Kitano, suyoshi; Kato, Hiroshi; Yamamoto, Takashi; Koashi, Masato; Imoto, Nobuyuki |
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Wide-band quantum interface for visible-totelecommunication wavelength conversion |
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Journal Article |
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2011 |
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Nature Communications |
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Nat. Comm. |
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2 |
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5 |
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Although near-infrared photons in telecommunication bands are required for long-distance quantum communication, various quantum information tasks have been performed by using visible photons for the past two decades. Recently, such visible photons from diverse media including atomic quantum memories have also been studied. Optical frequency down-conversion from visible to telecommunication bands while keeping the quantum states is thus required for bridging such wavelength gaps. Here we report demonstration of a quantum interface of frequency down-conversion from visible to telecommunication bands by using a nonlinear crystal, which has a potential to work over wide bandwidths, leading to a high-speed interface of frequency conversion. We achieved the conversion of a picosecond visible photon at 780 nm to a 1,522-nm photon, and observed that the conversion process retained entanglement between the down-converted photon and another photon. |
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764 |
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Crespi, Andrea; Ramponi, Roberta; Osellame, Roberto; Sansoni, Linda; Bongioanni, Irene; Sciarrino, Fabio; Vallone, Giuseppe; Mataloni, Paolo |
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Integrated photonic quantum gates for polarization qubits |
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2011 |
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Nature Communications |
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Nat. Comm. |
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2 |
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566 |
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6 |
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The ability to manipulate quantum states of light by integrated devices may open new perspectives both for fundamental tests of quantum mechanics and for novel technological applications. However, the technology for handling polarization-encoded qubits, the most commonly adopted approach, is still missing in quantum optical circuits. Here we demonstrate the first integrated photonic controlled-NOT (CNOT) gate for polarization-encoded qubits. This result has been enabled by the integration, based on femtosecond laser waveguide writing, of partially polarizing beam splitters on a glass chip. We characterize the logical truth table of the quantum gate demonstrating its high fidelity to the expected one. In addition, we show the ability of this gate to transform separable states into entangled ones and vice versa. Finally, the full accessibility of our device is exploited to carry out a complete characterization of the CNOT gate through a quantum process tomography. |
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Berlín, Guido; Brassard, Gilles; Bussières, Félix; Godbout, Nicolas; Slater, Joshua A.; Tittel, Wolfgang |
Title |
Experimental loss-tolerant quantum coin flipping |
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Journal Article |
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2011 |
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Nature Communications |
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Nat. Comm. |
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2 |
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561 |
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7 |
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Coin flipping is a cryptographic primitive in which two distrustful parties wish to generate a random bit to choose between two alternatives. This task is impossible to realize when it relies solely on the asynchronous exchange of classical bits: one dishonest player has complete control over the final outcome. It is only when coin flipping is supplemented with quantum communication that this problem can be alleviated, although partial bias remains. Unfortunately, practical systems are subject to loss of quantum data, which allows a cheater to force a bias that is complete or arbitrarily close to complete in all previous protocols and implementations. Here we report on the first experimental demonstration of a quantum coin-flipping protocol for which loss cannot be exploited to cheat better. By eliminating the problem of loss, which is unavoidable in any realistic setting, quantum coin flipping takes a significant step towards real-world applications of quantum communication. |
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766 |
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