Free-space quantum key distribution with Rb vapor filters

Shan, Xin; Sun, Xiujie; Luo, Jun; Zhan, Meng

doi:10.1063/1.2387867

Cited by 52 publications

(37 citation statements)

References 18 publications

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“…The sodium Fraunhofer lines are comparable "dim" as the H-alpha line. The use of a Faraday filter, which again reduces the background, could again reduce the sun's background contribution [58].…”

Section: Discussionmentioning

confidence: 99%

An atomic spectrum recorded with a single-molecule light source

et al. 2016

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Section: Discussionmentioning

confidence: 99%

An atomic spectrum recorded with a single-molecule light source

et al. 2016

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“…[11][12][13] Demonstrations of free-space QKD have been carried out successfully, including implementations over terrestrial 12,[14][15][16][17][18] and ground-air quantum channels. 18,19 Free-space quantum channels present a number of practical challenges for QKD.…”

Section: Introductionmentioning

confidence: 99%

“…FOVs previously discussed in the literature are sufficiently large to avoid turbulence-induced signal loss. [14][15][16]18,22,24 It has been discussed that improved tracking, or wavefront tilt correction, in a QKD receiver can improve the signal at small FOVs. 17,20,30,31 Recently, we presented preliminary results from numerical simulations showing that implementing higher-order adaptive optics (AO) at reduced FOVs in a QKD ground-station receiver can significantly improve SKG rates in daytime and enable SKG under conditions where it would otherwise be prohibited.…”

Section: Introductionmentioning

confidence: 99%

“…This includes a demonstration conducted at a low daytime sky radiance using a dielectric spectral filter 14 and a demonstration conducted at significantly higher radiance using an atomic-line spectral filter. 15 System-level analyses for implementations linking lowEarth orbit (LEO) satellites to terrestrial ground stations support plans for full-scale satellite demonstrations. 18,[20][21][22][23][24][25][26][27] Studies have considered both upward and downward propagating signal photons and concluded downlinks offer the advantage of lower transmitter-to-receiver aperture coupling losses due to the effects of atmospheric turbulence.…”

Section: Introductionmentioning

confidence: 99%

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Adaptive spatial filtering of daytime sky noise in a satellite quantum key distribution downlink receiver

et al. 2016

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Abstract. Spatial filtering is an important technique for reducing sky background noise in a satellite quantum key distribution downlink receiver. Atmospheric turbulence limits the extent to which spatial filtering can reduce sky noise without introducing signal losses. Using atmospheric propagation and compensation simulations, the potential benefit of adaptive optics (AO) to secure key generation (SKG) is quantified. Simulations are performed assuming optical propagation from a low-Earth-orbit satellite to a terrestrial receiver that includes AO. Higherorder AO correction is modeled assuming a Shack-Hartmann wavefront sensor and a continuous-face-sheet deformable mirror. The effects of atmospheric turbulence, tracking, and higher-order AO on the photon capture efficiency are simulated using statistical representations of turbulence and a time-domain wave-optics hardware emulator. SKG rates are calculated for a decoy-state protocol as a function of the receiver field of view for various strengths of turbulence, sky radiances, and pointing angles. The results show that at fields of view smaller than those discussed by others, AO technologies can enhance SKG rates in daylight and enable SKG where it would otherwise be prohibited as a consequence of background optical noise and signal loss due to propagation and turbulence effects. Keywords: quantum key distribution; adaptive optics; decoy states; quantum information; cryptography; sky radiance.Paper 151557P received Nov. 5, 2015; accepted for publication Dec. 24, 2015; published online Feb. 2, 2016; corrected Apr. 26, 2016. IntroductionThe threat quantum computing poses to public key cryptography is motivating the development of alternatives to modern key sharing techniques that rely on computational complexity for security.1,2 Presently, there is interest in developing quantum key distribution (QKD), presented by Bennett and Brassard in 1984 (BB84), as a provably secure alternative.2-5 QKD lends itself to mathematical proofs of theoretical security and offers the potential for secure generation of symmetric encryption keys in real time over optical channels.

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“…These atomic Faraday filters are imaging filters [9] with a large field of view [10], and can be engineered to be low loss at the signal frequency [11]. This makes them the filter of choice for many applications, for example, they are used in atmospheric lidar [11][12][13][14], Brillouin lidar [15,16], Doppler velocimetry [17,18], free-space communications [19] and quantum key distribution [20], quantum optics [21], filtering Raman light [22], optical limitation [23], and laser frequency stabilisation [24][25][26][27][28].…”

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confidence: 99%

Atomic Faraday filter with equivalent noise bandwidth less than 1 GHz

et al. 2015

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We demonstrate an atomic bandpass optical filter with an equivalent noise bandwidth less than 1 GHz using the D1 line in a cesium vapor. We use the ElecSus computer program to find optimal experimental parameters, and find that for important quantities the cesium D1 line clearly outperforms other alkali metals on either D-lines. The filter simultaneously achieves a peak transmission of 77%, a passband of 310 MHz and an equivalent noise bandwidth of 0.96 GHz, for a magnetic field of 45.3 gauss and a temperature of 68.0• C. Experimentally, the prediction from the model is verified. The experiment and theoretical predictions show excellent agreement.The Faraday effect in atomic media has come to be used for a wide range of applications, including creating macroscopic entanglement [1], GHz bandwidth measurements [2], non-destructive imaging [3], magnetometry [4], off-resonance laser frequency stabilization [5,6], and creating an optical isolator [7].Another application of increasing interest is utilizing the Faraday effect to create ultra-narrow bandwidth optical filters [8], of the order of a GHz width. These atomic Faraday filters are imaging filters [9] with a large field of view [10], and can be engineered to be low loss at the signal frequency [11]. This makes them the filter of choice for many applications, for example, they are used in atmospheric lidar [11][12][13][14] [9,24,25,[31][32][33][34], potassium [18,35,36], rubidium [37][38][39], and cesium [23,40,41]. A Faraday filter on the cesium D 1 line (894 nm) could be useful for quantum optics experiments which utilize the the Cs D 1 line [42], and could aid filtering degenerate photon-pairs at 894 nm in a similar way to that shown for 795 nm [21].In this letter we demonstrate the technique of using computer optimization to find optimal working parameters for a Faraday filter. Using this technique we find that a Faraday filter working at the Cs D 1 line has superior performance when compared to similar linear Faraday filters working with different elements and/or transitions. Experimentally, we verify the prediction of the model, and achieve a linear Faraday filter with the best performance to date.

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Free-space quantum key distribution with Rb vapor filters

Cited by 52 publications

References 18 publications

An atomic spectrum recorded with a single-molecule light source

An atomic spectrum recorded with a single-molecule light source

Adaptive spatial filtering of daytime sky noise in a satellite quantum key distribution downlink receiver

Atomic Faraday filter with equivalent noise bandwidth less than 1 GHz

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