Differential-phase-shift quantum key distribution experiment with a planar light-wave circuit Mach–Zehnder interferometer

Honjo, Toshimori; Inoue, Kyo; Takahashi, Hiroshi

doi:10.1364/ol.29.002797

Cited by 131 publications

(130 citation statements)

References 7 publications

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“…We employed the spontaneous four-wave mixing (SFWM) process in dispersionshifted fiber (DSF) [8,9], with which we obtained quantum correlated photon pairs with narrow bandwidths. To observe two-photon interference, we used 1-bit delay interferometers made of planar lightwave circuits (PLC), which are silica-based optical waveguides fabricated on silicon substrates [14]. The excellent stability of the PLC interferometers enabled long-term measurements to be performed without feedback control.…”

mentioning

confidence: 99%

Generation of1.5−μmband time-bin entanglement using spontaneous fiber four-wave mixing and planar light-wave circuit interferometers

2005

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This paper reports 1.5-µm band time-bin entanglement generation. We employed a spontaneous four-wave mixing process in a dispersion shifted fiber, with which correlated photon pairs with very narrow bandwidths were generated efficiently. To observe two-photon interference, we used planar lightwave circuit based interferometers that were operated stably without feedback control. As a result, we obtained coincidence fringes with 99 % visibilities after subtracting accidental coincidences, and successfully distributed entangled photons over 20-km standard single-mode fiber without any deterioration in the quantum correlation.PACS numbers: 42.50. Dv, 42.65.Lm, 03.67.Hk In recent years, the generation and distribution of entangled photon pairs have been studied intensively with a view to realizing such forms of quantum communication as quantum cryptography [1,2], quantum teleportation [3] and quantum repeaters [4]. Although practical entanglement sources based on parametric down conversion (PDC) have been reported and widely used in the short wavelength band [5,6], what is needed most for scalable quantum communication networks over optical fiber is a practical entanglement source in the 1.5-µm band, where silica fiber has its minimum loss. Several polarization entanglement sources in the 1.5-µm band have already been reported [7,8,9,10]. However, when transmitting polarization entangled photons over optical fiber, polarization mode dispersion (PMD) causes decoherence, which limits the transmission length. Therefore, polarization entanglement is not the best choice for quantum communication over optical fiber.Time-bin entanglement has been proposed to overcome this problem [11]. This scheme is based on qubits spanned by two time slots instead of two polarization modes, and so is unaffected by PMD. Although degenerated photon pairs in the 1.3-µm band [11] and nondegenerated photon pairs in the 1.3/1.5-µm band [12] have been reported with this scheme, the use of photon pairs where both photons are in the 1.5-µm band is obviously the most effective way of increasing the transmission length. Recently, a Hong-Ou-Mandel experiment using quantum correlated photon pairs both in the 1.5-µm band was demonstrated by Halder et al. [13]. However, the direct observation of the degree of entanglement on time-bin entangled photons in the 1.5-µm band has * Electronic address: htakesue@will.brl.ntt.co.jp; yet to be achieved. The large bandwidths of the previous entangled photon-pair sources pose another problem. Although there have been a few reports on entangled photon-pair sources with narrow bandwidths [9,13], most of the previous time-bin entanglement experiments employed PDC that generated photon pairs with a typical bandwidth of ∼10 nm [12]. This relatively large bandwidth made it difficult to distribute such photons over a standard single-mode fiber (SMF) with a zero dispersion wavelength of ∼1.3 µm, because of the pulse broadening caused by the large chromatic dispersion of the SMF. Since most installed fibers are standard ...

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confidence: 99%

Generation of1.5−μmband time-bin entanglement using spontaneous fiber four-wave mixing and planar light-wave circuit interferometers

2005

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“…6 and 7, we plot the key generation rate and the corresponding optimal Alice's mean photon numbers (α A ) as a function of the distance between Alice and Bob. In the figures, we define |δ| that satisfies η ex = tan δ 2 2 = 10 −3 as δ 0 (∼ 0.063), where η ex = 10 −3 is the typical order of η ex in some experiments [29]. We have confirmed that we cannot generate the key when η ex = 10 −3 .…”

Section: A Phase Encoding Scheme Imentioning

confidence: 60%

Phase encoding schemes for measurement-device-independent quantum key distribution with basis-dependent flaw

et al. 2012

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In this paper, we study the unconditional security of the so-called measurement device independent quantum key distribution (MDIQKD) with the basis-dependent flaw in the context of phase encoding schemes. We propose two schemes for the phase encoding, the first one employs a phase locking technique with the use of non-phase-randomized coherent pulses, and the second one uses conversion of standard BB84 phase encoding pulses into polarization modes. We prove the unconditional security of these schemes and we also simulate the key generation rate based on simple device models that accommodate imperfections. Our simulation results show the feasibility of these schemes with current technologies and highlight the importance of the state preparation with good fidelity between the density matrices in the two bases. Since the basis-dependent flaw is a problem not only for MDIQKD but also for standard QKD, our work highlights the importance of an accurate signal source in practical QKD systems. Note: We include the erratum of this paper in Appendix C. The correction does not affect the validity of the main conclusions reported in the paper, which is the importance of the state preparation in MDIQKD and the fact that our schemes can generate the key with the practical channel mode that we have assumed.

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“…As has been shown, WCP based protocols have a security threat, since an eavesdropper can perform a photon number splitting attack against the protocol (Inoue et al, 2003), (Honjo et al, 2004). These kinds of attacks are based on the fact that some weak coherent pulses contain more than one photon in the same polarization state, which provides information to the eavesdropper without any disturbance.…”

Section: The Dps Qkd Protocolmentioning

confidence: 99%

“…These kinds of attacks are based on the fact that some weak coherent pulses contain more than one photon in the same polarization state, which provides information to the eavesdropper without any disturbance. The DPS protocol is robust against such photon number splitting attacks in practice, however a theoretical lower bound on the security of the protocol is still missing from the literature (Inoue et al, 2003), (Honjo et al, 2004). The working mechanism of the DPS QKD protocol is based on the same idea as the B92 protocol (Bennett, 1992): even two non-orthogonal quantum states are sufficient to perform a secure quantum key distribution.…”

Section: The Dps Qkd Protocolmentioning

confidence: 99%

Secure Long-Distance Quantum Communication over Optical Fiber Quantum Channels

Gyöngyösi¹,

Imre²

2012

Optical Fiber Communications and Devices

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Differential-phase-shift quantum key distribution experiment with a planar light-wave circuit Mach–Zehnder interferometer

Cited by 131 publications

References 7 publications

Generation of1.5−μmband time-bin entanglement using spontaneous fiber four-wave mixing and planar light-wave circuit interferometers

Generation of1.5−μmband time-bin entanglement using spontaneous fiber four-wave mixing and planar light-wave circuit interferometers

Phase encoding schemes for measurement-device-independent quantum key distribution with basis-dependent flaw

Secure Long-Distance Quantum Communication over Optical Fiber Quantum Channels

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