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Difficulty: Very hardScience, Emerging Technology, and Space Missions in News

With reference to recent global advancements in quantum computing and satellite-based quantum communications, specifically regarding quantum key distribution (QKD) networks and optical ground stations, which of the following statements are correct?

  1. Satellite-based QKD utilizes photon entanglement to generate shared secret keys across continental distances without relying on trusted nodes for security.Answer
  2. Atmospheric turbulence and daylight background noise pose major technical hurdles, requiring adaptive optics and narrow spectral filtering for daytime quantum optical links.Answer
  3. C
    Quantum signals can be amplified across interplanetary distances using standard fiber-optic Erbium-Doped Fiber Amplifiers (EDFAs) without disturbing quantum superposition states.
  4. Low Earth Orbit (LEO) satellites are preferred over Geostationary Earth Orbit (GEO) satellites for initial quantum communication constellations primarily because GEO satellites suffer higher free-space path loss and diffraction losses.Answer

Answer

The correct statements are those describing entanglement-based QKD security across continental distances, the atmospheric mitigation techniques of adaptive optics and spectral filtering, and the orbital altitude selection based on free-space path loss.
Satellite-based QKD using entangled photon pairs ensures security through quantum non-locality without requiring trusted orbital nodes. Furthermore, free-space transmission faces severe atmospheric turbulence and solar background noise, requiring adaptive optics and narrow spectral filters for operation. Finally, low Earth orbits are favored over geostationary orbits because the dramatically lower free-space path loss allows detectable single-photon transmission rates given current telescope aperture sizes.

Step-by-Step Solution

1
Evaluate statement on satellite-based entanglement QKD.
Entanglement-based QKD protocols (like E91) establish security via Bell state measurement and quantum non-locality. The satellite acts purely as a source of entangled pairs rather than a trusted relay, making the statement correct.
Understanding the fundamental distinction between trusted-relay QKD and entanglement-based untrusted relay QKD.
2
Evaluate atmospheric challenges in optical quantum communications.
Free-space optical quantum links are heavily constrained by atmospheric turbulence causing wavefront error and ambient solar background noise during daylight. Mitigations include spatial, temporal, and spectral filtering combined with adaptive optics, making the statement correct.
Analyzing optical engineering constraints in free-space quantum transmission.
3
Evaluate the feasibility of standard optical amplifiers for quantum signals.
Conventional EDFAs rely on stimulated emission which destroys quantum states and violates the No-Cloning Theorem (dψ→dψ⊗dψd\psi \rightarrow d\psi \otimes d\psi). Quantum repeaters, not standard amplifiers, are required to extend quantum communication distances. Thus, the statement is incorrect.
Applying quantum mechanical principles regarding state measurement and signal replication limits.
4
Evaluate orbital dynamics and signal attenuation differences between LEO and GEO.
Free-space path loss scales with the square of distance (Lp∝d2L_p \propto d^2). Signal attenuation over tens of thousands of kilometers (GEO) reduces single-photon count rates below detector background noise levels, favoring LEO deployment for initial operational quantum constellations. Thus, the statement is correct.
Synthesizing orbital physics with optical attenuation parameters.

Key Concept

Quantum Key Distribution (QKD) and Satellite-based Quantum Communications
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Topics

Science, Emerging Technology, and Space Missions in News

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