Secure free-space key exchange to 1.9km and beyond

Rarity, John; Tapster, P R; Gorman, P.M.

doi:10.1080/09500340108240895

Cited by 23 publications

(16 citation statements)

References 18 publications

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“…Wide bandgap semiconductor QDs based on group IIInitrides present additional advantages, as high-temperature operation [11][12][13][14] and wide spectral tunability from the deep ultraviolet to telecommunication wavelengths. The III-nitridebased quantum emitters operating in the ultraviolet-visible region are especially beneficial for free space communications [15]. Moreover, highly polarized light emission originating from valence-band mixing effects is typical of III-nitrides.…”

mentioning

confidence: 99%

Blue-to-green single photons from InGaN/GaN dot-in-a-nanowire ordered arrays

Chernysheva¹,

Gačević²,

García-Lepetit³

et al. 2015

EPL

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-Single photon emitters (SPEs) are at the basis of many applications for quantum information management. Semiconductor-based SPEs are best suited for practical implementations because of high design flexibility, scalability and integration potential in practical devices. Single photon emission from ordered arrays of InGaN nano-disks embedded in GaN nanowires is reported. Intense and narrow optical emission lines from quantum dot-like recombination centers are observed in the blue-green spectral range. Characterization by electron microscopy, cathodoluminescence and micro-photoluminescence indicate that single photons are emitted from regions of high In concentration in the nano-disks due to alloy composition fluctuations. Single photon emission is determined by photon correlation measurements showing deep antibunching minima in the second order correlation function. The present results are a promising step towards the realization of on-site/on-demand single photon sources in the blue-green spectral range operating in the GHz frequency range at high temperatures.Introduction. -Single photons are ideal "flying" qubits to convey quantum information between distant nodes of a quantum network. Reliable and controlled generation of single photons is therefore a crucial step to develop applications for quantum communication, quantum information processing and quantum metrology [1,2]. Single photons can be emitted in principle by material entities possessing discrete energy levels, as they need a finite time to "recharge" after emission of one photon. The standard method to assess single photon emission is to measure the second order photon correlation function by Hanbury-Brown and Twiss (HBT) interferometry. As shown in Fig. 1, single photons are either reflected or transmitted by a beam splitter, so that the probability of simultaneous detection in the two detectors of the interferometer is zero. The detection events are stored in a Time-Correlated Single Photon Counter (TCSPC), and the resulting correlation function g 2 (τ) shows an

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confidence: 99%

Blue-to-green single photons from InGaN/GaN dot-in-a-nanowire ordered arrays

Chernysheva¹,

Gačević²,

García-Lepetit³

et al. 2015

EPL

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“…Furthermore photons can be easily generated, manipulated and transmitted over large distances via optical fibres or free-space links. Since the maximal distance for the distribution of quantum entanglement in optical fibres is limited to the order [2, 3, 4, 5] of ∼ 100 km, the most promising option for testing quantum entanglement on a global scale is currently free-space transmission, ultimately using satellites and ground stations [6].In recent years, various free-space quantum communication experiments with weak coherent laser pulses [7,8,9,10,11] and entangled photons [12,13,14,15] have been performed on ever larger distance scales and with increasing bit rates. The to-date most advanced test bed for free-space distribution of entanglement is a 144 km free-space link between two Canary Islands, where the successful transmission of one photon of an entangled pair was recently achieved [16].…”

mentioning

confidence: 99%

“…In recent years, various free-space quantum communication experiments with weak coherent laser pulses [7,8,9,10,11] and entangled photons [12,13,14,15] have been performed on ever larger distance scales and with increasing bit rates. The to-date most advanced test bed for free-space distribution of entanglement is a 144 km free-space link between two Canary Islands, where the successful transmission of one photon of an entangled pair was recently achieved [16].…”

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confidence: 99%

High-fidelity transmission of entanglement over a high-loss free-space channel

et al. 2009

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Quantum entanglement enables tasks not possible in classical physics. Many quantum communication protocols [1] require the distribution of entangled states between distant parties. Here we experimentally demonstrate the successful transmission of an entangled photon pair over a 144 km free-space link. The received entangled states have excellent, noise-limited fidelity, even though they are exposed to extreme attenuation dominated by turbulent atmospheric effects. The total channel loss of 64 dB corresponds to the estimated attenuation regime for a two-photon satellite quantum communication scenario. We confirm that the received two-photon states are still highly entangled by violating the CHSH inequality by more than 5 standard deviations. From a fundamental point of view, our results show that the photons are subject to virtually no decoherence during their 0.5 ms long flight through air, which is encouraging for future world-wide quantum communication scenarios.Entanglement is at the heart of many peculiarities encountered in quantum mechanics and has allowed many ground-breaking tests on the fundamentals of nature. Entangled photons are ideal tools to investigate the laws of quantum mechanics over long distances and timescales since they are not subject to decoherence. Furthermore photons can be easily generated, manipulated and transmitted over large distances via optical fibres or free-space links. Since the maximal distance for the distribution of quantum entanglement in optical fibres is limited to the order [2, 3, 4, 5] of ∼ 100 km, the most promising option for testing quantum entanglement on a global scale is currently free-space transmission, ultimately using satellites and ground stations [6].In recent years, various free-space quantum communication experiments with weak coherent laser pulses [7,8,9,10,11] and entangled photons [12,13,14,15] have been performed on ever larger distance scales and with increasing bit rates. The to-date most advanced test bed for free-space distribution of entanglement is a 144 km free-space link between two Canary Islands, where the successful transmission of one photon of an entangled pair was recently achieved [16]. In the present experiment we demonstrate a fundamentally more interesting scenario by sending both photons of an entangled pair over this free-space channel. By violating a Clauser-HorneShimony-Holt (CHSH) Bell inequality [17] we find that entanglement is highly stable over these long time spans -the photon-pair flight time of ∼ 0.5 ms is the longest lifetime of photonic Bell states reported so far, almost twice as long as the previous high [4,5] of ∼ 250 µs.The achieved noise-limited fidelity paves the way for free-space implementations of quantum communication protocols that require the transmission of two photons, e.g. quantum dense coding [18], entanglement purification [19], quantum teleportation [20] and quantum key distribution without a shared reference frame [21]. From a technological perspective, the overall two-photon loss bridged in our exper...

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“…The accidental detection rate due to the solar background was minimized using a combination of narrowband filters, short time windows, and a small solid angle over which the signal was accepted. A number of other groups [26][27] have now demonstrated similar systems over larger ranges, and satellite systems of this kind are being considered. These systems will probably have relatively high costs and small bandwidths.…”

Section: Challenges In Quantum Communicationsmentioning

confidence: 99%

Quantum Logic Using Linear Optics

Franson¹,

Jacobs²,

Pittman³

2005

Optical Science and Engineering

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Abstract:In order for quantum communications systems to become widely used, it will probably be necessary to develop quantum repeaters that can extend the range of quantum key distribution systems and correct for errors in the transmission of quantum information.Quantum logic gates based on linear optical techniques appear to be a promising approach for the development of quantum repeaters, and they may have applications in quantum computing as well. Here we describe the basic principles of logic gates based on linear optics, along with the results from several experimental demonstrations of devices of this kind. A prototype source of single photons and a quantum memory device for photons are also discussed. These devices can be combined with a four-qubit encoding to implement a quantum repeater.

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Secure free-space key exchange to 1.9km and beyond

Cited by 23 publications

References 18 publications

Blue-to-green single photons from InGaN/GaN dot-in-a-nanowire ordered arrays

Blue-to-green single photons from InGaN/GaN dot-in-a-nanowire ordered arrays

High-fidelity transmission of entanglement over a high-loss free-space channel

Quantum Logic Using Linear Optics

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