Entanglement distribution over 300 km of fiber

Inagaki, Terumi; Matsuda, Nobuyuki; Tadanaga, O.; Asobe, Masaki; Takesue, Hiroki

doi:10.1364/oe.21.023241

Cited by 190 publications

(132 citation statements)

References 32 publications

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“…However, this method is known to be sensitive to polarization mode dispersion in optical fibers [11]. As an alternative, entanglement in the time-energy basis may be employed, wherein quantum information is encoded in the arrival time of photons, and long-distance fiber transmission over 300 km is possible [12]. The approach of using time-energy entangled photons was first formulated by Franson, with photon pairs created in an atomic decay process and two unbalanced interferometers [13].…”

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confidence: 99%

Franson Interference Generated by a Two-Level System

2017

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We report a Franson interferometry experiment based on correlated photon pairs generated via frequency-filtered scattered light from a near-resonantly driven two-level semiconductor quantum dot. In contrast to spontaneous parametric down conversion and four-wave mixing, this approach can produce single pairs of correlated photons. We have measured a Franson visibility as high as 66%, which goes beyond the classical limit of 50% and approaches the limit of violation of Bell's inequalities (70.7%).Introduction-Entanglement is perhaps the most intriguing of all physical phenomena, and was famously challenged by Einstein, Podolsky and Rosen (EPR) in 1935 [1]. The EPR paradox led to Bell's inequalities [2] which were since tested by numerous experiments [3] including recent "loophole-free" tests [4][5][6] that have conclusively demonstrated that entanglement cannot be explained using local hidden variable theories.Most experiments have employed photons that are entangled in the energy and polarization degrees of freedom [7][8][9][10]. However, this method is known to be sensitive to polarization mode dispersion in optical fibers [11]. As an alternative, entanglement in the time-energy basis may be employed, wherein quantum information is encoded in the arrival time of photons, and long-distance fiber transmission over 300 km is possible [12]. The approach of using time-energy entangled photons was first formulated by Franson, with photon pairs created in an atomic decay process and two unbalanced interferometers [13]. Franson-type experiments have stimulated a plethora of research activities and have been extensively used for Bell tests in quantum optics [14][15][16].Today, entangled photon pairs for Franson experiments are primarily produced via spontaneous parametric down conversion (SPDC) or four-wave mixing (FWM), following two main methods. In time-energy experiments [17,18], a nonlinear medium is pumped by a continuous monochromatic laser and emission times of the photons have an uncertainty equal to the coherence time of the pump laser. On the other hand in time-bin experiments [14,19], a nonlinear medium is pumped by pulses that have previously passed through an unbalanced interferometer, leading to a "which-path" ambiguity in emission time. However, either method provides a nondeterministic pair generation, leading to limitations on the accuracy and security of quantum communication.Single-photon sources, based on single atoms, ions, impurity centers and quantum dots (QDs) [20], have emerged as alternatives [21,22], emitting no more than a single pair during any given cascade decay. In particular, intense research efforts using InAs semiconductor QDs have enabled the generation of triggered photon pairs at

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confidence: 99%

Franson Interference Generated by a Two-Level System

2017

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“…In order to realize quantum communication system, a long-distance entanglement distribution is also important, and recently experiments of an entanglement distribution over 300 km of the optical fiber has been achieved by using SSPDs [45]. Very recently, a new scheme named the measurement-device-independent QKD (MDI-QKD) protocol, in which the security never relies on the measurement, has been actively studied, and high-performance SSPDs were implemented also in the MDI-QKD systems as a key device [46].…”

Section: Quantum Communicationmentioning

confidence: 99%

Recent Progress and Application of Superconducting Nanowire Single-Photon Detectors

Yamashita

Miki

Terai

2017

IEICE Trans. Electron.

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SUMMARYIn this review, we present recent advances relating to superconducting nanowire single-photon detectors (SSPDs or SNSPDs) and their broad range of applications. During a period exceeding ten years, the system performance of SSPDs has been drastically improved, and lately excellent detection efficiencies have been realized in practical systems for a wide range of target photon wavelengths. Owing to their advantages such as high system detection efficiency, low dark count rate, and excellent timing jitter, SSPDs have found application in various research fields such as quantum information, quantum optics, optical communication, and also in the life sciences. We summarize the photon detection principle and the current performance status of practical SSPD systems. In addition, we introduce application examples in which SSPDs have been applied.

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“…It has been suggested that a design by Franson [23] could be used to achieve the same unconditional security as traditional QKD protocols. Several experiments have evaluated this Franson-type setup [24][25][26][27][28][29][30][31], however this thesis will show that there are complications when basing QKD on energy-time phenomena.…”

Section: Cryptography and The Quantum Worldmentioning

confidence: 99%

“…Using the Franson interferometer we can also perform QKD to generate a secret key and this has also been tested experimentally QKD [24][25][26][27][28][29][30][31]. Keep in mind, however, that the Franson setup uses a postselection step.…”

Section: The Franson Interferometermentioning

confidence: 99%

A Classical-Light Attack on Energy-Time Entangled Quantum Key Distribution, and Countermeasures

Jogenfors¹

2015

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Quantum key distribution (QKD) is an application of quantum mechanics that allows two parties to communicate with perfect secrecy. Traditional QKD uses polarization of individual photons, but the development of energytime entanglement could lead to QKD protocols robust against environmental effects. The security proofs of energy-time entangled QKD rely on a violation of the Bell inequality to certify the system as secure. This thesis shows that the Bell violation can be faked in energy-time entangled QKD protocols that involve a postselection step, such as Franson-based setups. Using pulsed and phase-modulated classical light, it is possible to circumvent the Bell test which allows for a local hidden-variable model to give the same predictions as the quantum-mechanical description. We show that this attack works experimentally and also how energy-time-entangled systems can be strengthened to avoid our attack. v vi Populärvetenskaplig sammanfattningKvantkryptering är en tillämpning av kvantmekanik där fysikens lagar används för att kryptera information. Till skillnad mot klassisk kryptering, som bygger på matematiska problem som antas (men inte bevisats) vara svåra att forcera, kan kvantkryptering ge garanterad säkerhet. Inte ens en oändligt snabb dator kan kringgå hemligheter som krypterats på kvantmekanisk väg eftersom säkerheten kommer direkt från fysikens lagar. Vanligtvis bygger kvantkryptering på enstaka fotoner där polarisering bär information, men nackdelen med den metoden är att polarisering är relativt känslig för störningar. Därför har det på senare tid kommit en ny metod, energi-tidssnärjning, som antas vara mer robust och därmed kan vara mer lämpat till att användas i stor skala. Det mest kända protokollet som bygger på denna teknik är Fransons interferometer. Detta system har utvärderats av ledande forskargrupper runt om i världen, och under många år har man trott att det kan uppnå garanterad säkerhet. Denna avhandling kommer dock visa på en inbyggd, allvarlig svaghet som gör att en tredje part kan forcera säkerheten i Fransons interferometer utan att lämna spår efter sig. Följderna är påtagliga; kvantkryptering som baseras på Fransons interferometer kan avlyssnas och måste därför byta ut den grundläggande säkerhetsmekanismen. Bells olikhet i sin ursprungliga form kan luras att certifiera ett osäkert system som säkert, och vi avslutar med att ge förslag på möjliga förbättringar. vii viii

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Entanglement distribution over 300 km of fiber

Cited by 190 publications

References 32 publications

Franson Interference Generated by a Two-Level System

Franson Interference Generated by a Two-Level System

Recent Progress and Application of Superconducting Nanowire Single-Photon Detectors

A Classical-Light Attack on Energy-Time Entangled Quantum Key Distribution, and Countermeasures

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