Is Quantum Communication Secure?
What QKD guarantees, what it assumes, and how it compares with post-quantum cryptography.
Quantum Communication
IntermediateQuantum communication7 min read
By QuantumO Editorial · Scientific reviewer: not yet assigned · Published · Updated
In short
Quantum communication sends quantum states between locations, usually as photons through fibre or free space. It enables quantum key distribution, entanglement distribution between distant nodes, and protocols such as teleportation. Losses limit distance, so repeaters and satellite links are active areas of research.
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Visit the channelPhotons as carriers
Photons interact weakly with their environment, which makes them good messengers. Quantum information is encoded in properties such as polarisation or timing.
The cost is loss: fibre attenuates signal, and quantum signals cannot simply be amplified, because copying an unknown quantum state is impossible.
Extending range
Trusted-node networks relay keys through intermediate sites that must themselves be trusted. Quantum repeaters, which would remove that requirement using entanglement swapping and memories, remain a research goal.
Satellite links have demonstrated entanglement distribution over very long distances, bypassing fibre loss through free space.
Common misconceptions
- Claim: Quantum networks will replace the internet.
- More accurately: Quantum links are expected to complement classical networks for specific tasks such as key distribution, not to carry ordinary traffic.
Important terminology
- Entanglement
- Entanglement is a link between quantum systems such that the whole system has a definite description while its individual parts do not.
- Quantum teleportation
- Quantum teleportation is a protocol that transfers a quantum state from one location to another using shared entanglement and two classical bits.
- Measurement
- Measurement is the process that extracts a definite classical outcome from a quantum system, with probabilities set by its amplitudes.
Frequently asked questions
- What is quantum communication?
- The transmission of quantum states between locations, typically encoded in photons, supporting applications such as key distribution and entanglement sharing.
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Sources and further reading
Keep going
What Is Quantum Teleportation?
The protocol, step by step, and what it is not.
Quantum Entanglement
Correlations without communication — what Bell tests established and what they did not.