# [TECH-Idea] Quantum Internet & Quantum Cryptography
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**The quantum internet** is a communication network transmitting quantum states — entangled photon pairs, qubits — enabling unconditionally secure cryptography by quantum key distribution (QKD), distributed quantum computing, and quantum-enhanced sensing.
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## Overview
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**Quantum Key Distribution (QKD)**: any eavesdropping on a quantum channel collapses the quantum states, making interception physically detectable. Security is guaranteed by quantum mechanics, not computational hardness — immune to any future quantum or classical computer. The BB84 protocol (Bennett & Brassard, 1984) is the theoretical foundation.
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**Deployed systems**:
- China's QUESS satellite (Micius, 2016): demonstrated QKD over 1,200 km (2017), intercontinental QKD Europe-China (2020), 4,600 km ground network.
- Toshiba: commercial QKD systems deployed in London, Tokyo, and New York financial networks.
- ID Quantique (Geneva): commercial QKD for banking and government.
- EU Quantum Flagship: EUR 1B, 10-year programme; EuroQCI (quantum communication infrastructure) connecting all EU capitals by 2027.
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**Quantum repeaters** (enabling global reach): require quantum memory + entanglement swapping. Currently limited to ~100 km without repeaters. QuTech (Delft), Innsbruck, and MIT are building repeater prototypes; commercial repeaters 5–10 years away.
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**Threat context**: A sufficiently powerful quantum computer running Shor's algorithm breaks RSA and ECC encryption — the basis of all internet security. "Harvest now, decrypt later" attacks (adversaries recording encrypted traffic today to decrypt once a quantum computer exists) make this an urgent present-day concern.
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## Key Actors
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China National Space Administration / QUESS program, Toshiba Research Europe, ID Quantique, QuTech (Delft, AWS partnership), Amazon Braket Quantum Networking, BT Quantum (UK), AWS, JPMorgan Chase (active QKD user).
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## Economic Value
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Global cybersecurity market: USD 200B+/year (2023). QKD for government and finance: USD 10–20B/year by 2030 (Markets and Markets). Full quantum internet enabling distributed quantum computing: impossible to estimate, but analogous to valuing the internet in 1985. NIST post-quantum cryptography standards (finalised 2024) provide a classical alternative — QKD competes with these for high-security government/military use.
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## Notes
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The US National Quantum Initiative Act (2018, USD 1.2B), EU Quantum Flagship (EUR 1B), and China's programme (USD 15B+ estimated) are the three major governmental commitments.
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## Discovery Character
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**Surprise level**: Moderate — theoretically clear since 1984. The surprise was China's pace and ambition (satellite QKD in 2017 was earlier than Western estimates). The technical challenge of quantum repeaters has been harder than initially anticipated.
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**Mode**: Systematic-engineering pursuit of clear theoretical goals. The quantum repeater challenge (quantum memory + entanglement swapping at room temperature) is the key unsolved engineering problem.
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## What This Enables
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This node is a current frontier — a global quantum internet would enable distributed quantum computing and next-generation secure communication that are themselves speculative.
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# Parents
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* [TECH] Quantum Computing Hardware⏎