Quantum key distribution over 120 km using ultrahigh purity single-photon source and superconducting single-photon detectors

Takemoto, Kazuhiro; Nambu, Yasusada; Miyazawa, T.; Sakuma, Yoshiki; Yamamoto, Tsuyoshi; Yorozu, Shinichi; Arakawa, Yasuhiko

doi:10.1038/srep14383

Cited by 190 publications

(163 citation statements)

References 39 publications

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“…This complements other related works involving hybrid optical states using spatial (path and optical orbital angular momentum) and polarisation modes [20][21][22][23]. It also substantiates the oftrepeated claim that combining different photonic encodings [24,25] is a practical tool for various quantum information tasks, for example studying the remote preparation of entangled states [26], complementarity [27], Bell inequalities [21,28,29], quantum key distribution implementations [30] and complete optical Bell state analysers [31,32]. Our first task consists of performing the quantum simulation of the perturbed coin.…”

Section: Experimental Implementationsupporting

confidence: 85%

Interfering trajectories in experimental quantum-enhanced stochastic simulation

et al. 2019

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Simulations of stochastic processes play an important role in the quantitative sciences, enabling the characterisation of complex systems. Recent work has established a quantum advantage in stochastic simulation, leading to quantum devices that execute a simulation using less memory than possible by classical means. To realise this advantage it is essential that the memory register remains coherent, and coherently interacts with the processor, allowing the simulator to operate over many time steps. Here we report a multi-time-step experimental simulation of a stochastic process using less memory than the classical limit. A key feature of the photonic quantum information processor is that it creates a quantum superposition of all possible future trajectories that the system can evolve into. This superposition allows us to introduce, and demonstrate, the idea of comparing statistical futures of two classical processes via quantum interference. We demonstrate interference of two 16-dimensional quantum states, representing statistical futures of our process, with a visibility of 0.96 ± 0.02.

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Section: Experimental Implementationsupporting

confidence: 85%

Interfering trajectories in experimental quantum-enhanced stochastic simulation

et al. 2019

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“…This was the case as single photon detectors had a low detection efficiency in the past and suffered from large dark counts at communication wavelengths . Recent progresses in the development of highly efficient single photon detectors at communication wavelengths makes the up‐conversion of single photons not necessary. However, wavelength converters are still attractive as they can convert single photons from quantum dots or ion traps, which usually emit in the ultraviolet to near infrared wavelength regime, to single photons at communication wavelengths.…”

Section: Emerging and Potential Future Applicationsmentioning

confidence: 99%

Status and Potential of Lithium Niobate on Insulator (LNOI) for Photonic Integrated Circuits

Boes

Corcoran

Chang

et al. 2018

Laser & Photonics Reviews

573

290

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Lithium niobate on insulator (LNOI) technology is revolutionizing the lithium niobate industry, enabling higher performance, lower cost and entirely new devices and applications. The availability of LNOI wafers has sparked significant interest in the platform for integrated optical applications, as LNOI offers the attractive material properties of lithium niobate, while also offering the stronger optical confinement and a high optical element integration density that has driven the success of more mature silicon and silicon nitride (SiN) photonics platforms. Due to some similarities between LNOI and SiN, established techniques and standards can readily be adapted to the LNOI platform including a significant array of interface approaches, device designs and also heterogeneous integration techniques for laser sources and photodetectors. In this contribution, we review the latest developments in this platform, examine where further development is necessary to achieve more functionalities in LNOI integrated optical circuits and make a few suggestions of interesting applications that could be realized in this platform.

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“…The simple model reproduces the measured behavior qualitatively. Figure 4 shows the intensity autocorrelation function g (2) (t) of the X luminescence line in Fig. 1(b).…”

Section: Arxiv:200107329v1 [Cond-matmes-hall] 21 Jan 2020mentioning

confidence: 99%

Single photon emission from droplet epitaxial quantum dots in the standard telecom window around a wavelength of 1.55 μm

Ha¹,

Mano²,

Dubos³

et al. 2020

Appl. Phys. Express

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We study the luminescence dynamics of telecom wavelength InAs quantum dots grown on InP(111)A by droplet epitaxy. The use of the ternary alloy InAlGaAs as a barrier material leads to photon emission in the 1.55 µm telecom C-band. The luminescence decay is well described in terms of the theoretical interband transition strength without the impact of nonradiative recombination. The intensity autocorrelation function shows clear anti-bunching photon statistics. The results suggest that our quantum dots are useful for constructing a practical source of single photons and quantum entangled photon pairs. This is the version of the article before peer review, as submitted to Applied Physics Express. The final published version will be available as an Open Access article from the journal's site.A source of single photons and quantum entangled photon pairs is a key device in vast quantum technologies. Semiconductor quantum dots are expected to serve as photon sources that can be operated very efficiently and deterministically. Numerous efforts have already been made to develop a practical quantum dot photon source. However, photon emission in the standard telecom band, particularly around a wavelength of 1.55 µm, which is the maximum transmission window of silica optical fibers, is a material challenge. Careful growth optimization is required to achieve a 1.55 µm emission 1-10 . Nevertheless, the well-known quantum dot growth based on the Stranski-Krastanow mode leads to an asymmetric dot shape, which is not favorable for entangled pair generation.The problem is ideally solved by using droplet epitaxy, which offers considerable freedom regarding the choice of materials and substrates 11 . The application of a C 3v symmetric (111)A surface to the growth substrate results in the creation of almost perfectly symmetric quantum dots, which can work in both the visible wavelength region 12,13 and the infrared telecom wavelength region 14,15 . Recently, the emission wavelength has been extended beyond 1.5 µm for InAs dots embedded in InAlGaAs on InP(111)A 16 . However, the previous samples were not sufficiently optimized: the dot density was too high for a single quantum dot to be isolated using standard micro optics. Moreover, the dot size distribution is relatively large so that careful dot selection is required to find a dot that emits at 1.55 µm.Here, we extend the droplet epitaxy scheme to achieve a purely 1.55 µm photon emission. We introduce the high temperature crystallization protocol, which has recently been applied to the GaAs material system 17,18 , to the InAs/InP material system in order to improve the a) Electronic mail: ha.neul@nims.go.jp b) Electronic mail: kuroda.takashi@nims.go.jp FIG. 1. (Color online) (b) The luminescence spectra of a large ensemble of InAs quantum dots in In0.52Al0.12Ga0.36As /InP(111)A at 12 K at different excitation powers. (b) The luminescence spectra of a single isolated InAs dot with a cw excitation of 40 nW. We focus on this dot in our time-resolved study. The inset shows an atomic fo...

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Quantum key distribution over 120 km using ultrahigh purity single-photon source and superconducting single-photon detectors

Cited by 190 publications

References 39 publications

Interfering trajectories in experimental quantum-enhanced stochastic simulation

Interfering trajectories in experimental quantum-enhanced stochastic simulation

Status and Potential of Lithium Niobate on Insulator (LNOI) for Photonic Integrated Circuits

Single photon emission from droplet epitaxial quantum dots in the standard telecom window around a wavelength of 1.55 μm

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