Differential phase shift quantum key distribution experiment over 105 km fibre

Takesue, Hiroki; Diamanti, Eleni; Honjo, Toshimori; Langrock, Carsten; Fejer, M. M.; Inoue, Kyo; Yamamoto, Yoshihisa

doi:10.1088/1367-2630/7/1/232

Cited by 144 publications

(128 citation statements)

References 32 publications

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“…Also, faked states exploiting detector efficiency mismatch can be constructed for energy-time encoding and differential phase shift keying QKD schemes [41,42,43,44,45]; see examples of faked states in Ref. [46].…”

Section: Discussionmentioning

confidence: 99%

Effects of detector efficiency mismatch on security of quantum cryptosystems

2006

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We suggest a type of attack on quantum cryptosystems that exploits variations in detector efficiency as a function of a control parameter accessible to an eavesdropper. With gated single-photon detectors, this control parameter can be the timing of the incoming pulse. When the eavesdropper sends short pulses using the appropriate timing so that the two gated detectors in Bob's setup have different efficiencies, the security of quantum key distribution can be compromised. Specifically, we show for the Bennett-Brassard 1984 (BB84) protocol that if the efficiency mismatch between 0 and 1 detectors for some value of the control parameter gets large enough (roughly 15:1 or larger), Eve can construct a successful faked-states attack causing a quantum bit error rate lower than 11%. We also derive a general security bound as a function of the detector sensitivity mismatch for the BB84 protocol. Experimental data for two different detectors are presented, and protection measures against this attack are discussed.

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Section: Discussionmentioning

confidence: 99%

Effects of detector efficiency mismatch on security of quantum cryptosystems

2006

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“…SHG, however, cannot be used for faint nonclassical states. In 2004, frequency up-conversion of single photons was achieved via nondegenerate sumfrequency generation [19] and used to increase the detection efficiency in quantum key distribution [20]. In [21] the nonclassical correlation between an up-converted photon and a reference photon was verified.…”

mentioning

confidence: 99%

“…We thus go beyond single-photon conversion [19][20][21]. With appropriate input states our setup is able to up-convert superpositions of coherent states with negative Wigner functions [5,6] as well as Einstein-Podolsky-Rosen entangled states [3,4].…”

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confidence: 99%

Quantum Up-Conversion of Squeezed Vacuum States from 1550 to 532 nm

et al. 2014

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Squeezed vacuum states constitute a particularly useful resource in quantum information as well as in quantum metrology. The frequency conversion of these states is important to provide the bridge between different wavelengths within a sequence of downstream applications and also to provide a way for squeezed-state generation at so-far inaccessible wavelengths. Here we demonstrate the external quantum up-conversion of carrier-light-free squeezed vacuum states for the first time. Our result proves that nondegenerate sum-frequency generation preserves the coherences that are present between photon pairs and higher-order photon pairs of the squeezed input state. DOI: 10.1103/PhysRevLett.112.073602 PACS numbers: 42.50.Dv, 03.67.-a, 07.60.Ly, 42.65.-k Frequency conversion constitutes a standard process for light fields in coherent states and mixtures thereof. Via frequency conversion, laser radiation can be shifted to wavelength regimes that are not directly accessible via state-of-the-art laser media. In particular, frequency upconversion is of high interest to increase the resolution in imaging and lithography [1] and to increase the sensitivity in phase measurements [2]. For light in nonclassical states, the task of frequency conversion is much more challenging. First, nonlinear processes are the more efficient the higher the light intensities, but the most practical and useful nonclassical states are extremely faint, for instance Fock states, squeezed vacuum states and superpositions of (dim) coherent states. Second, in order to preserve the distinct nonclassical properties of the input states high conversion efficiencies of ideally close to unity are mandatory.Optical fields in squeezed vacuum states consist of pairs and higher-order pairs of photons. The coherences between them give rise to a squeezed photon counting noise in a balanced homodyne detector. These states have been used for the realization of teleportation [3,4], superpositions of coherent states (Schrödinger kitten states) [5,6], and quantum key distribution [7,8], as well as quantum enhancements of spectroscopy [9], imaging [10,11], and weak-force measurements such as those performed in gravitationalwave detectors [12][13][14][15]. The absence of any bright carrier field makes squeezed vacuum states ideal for quantum communication and metrology since photon-phonon scattering from the carrier field (Brillouin scattering) easily spoils the squeezed vacuum states in the audio-and radiofrequency sideband [16,17].With their pioneering work in 1992, Huang and Kumar demonstrated quantum frequency conversion of a bright beam maintaining its nonclassical intensity correlation with another bright beam via second-harmonic generation (SHG) [18]. SHG, however, cannot be used for faint nonclassical states. In 2004, frequency up-conversion of single photons was achieved via nondegenerate sumfrequency generation [19] and used to increase the detection efficiency in quantum key distribution [20]. In [21] the nonclassical correlation between an up-converted p...

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“…From this viewpoint, the DPS protocol has been analyzed by Takesue et al (Takesue et al, 2005). In this section we show that the complexity of the DPS QKD protocol's security analysis can be decreased dramatically, using fast computational information geometric methods , (Gyongyosi & Imre, 2010a), (Nielsen et al, 2007), , (Nielsen & Nock, 2008a), (Nielsen & Nock, 2009).…”

Section: The Dps Qkd Protocolmentioning

confidence: 99%

“…QKD schemes were implemented over a 250 km long optical fiber, however these distances are still small compared to the distances in standard optical communication networks (Curty et al, 2008), (Inoue et al, 2003), (Honjo et al, 2004), (Kwiat et al, 2001), (Manderbach et al, 2007), (Takesue et al, 2005), (Stucki et al, 2009). The Six-state quantum cryptography protocol uses six polarization states to encode the logical bits in the qubits.…”

Section: Demonstration Of Qkdmentioning

confidence: 99%