Quantum Key Distribution and Qubits ECES Practice Questions (Page 3)

Questions 11–15

1. 11foundation · easy

   Which quantum principle guarantees that an eavesdropper cannot gain information without disturbing the quantum state?

   • AThe principle of quantum entanglement, which ensures that any measurement is instantly known to all parties.
   • BThe Heisenberg uncertainty principle, which limits the precision of simultaneous measurements.
   • CThe principle of quantum teleportation, which allows secure transfer without measurement.
   • DThe principle of quantum superposition, which allows a qubit to be in multiple states at once.
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2. 12foundation · easy

   What is the role of the no-cloning theorem in QKD security?

   • AIt prevents an eavesdropper from perfectly copying the quantum states carrying the key.
   • BIt ensures that the key can be transmitted without any errors.
   • CIt allows the legitimate parties to clone the key for backup purposes.
   • DIt allows the receiver to measure the qubit without disturbing it.
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4. 13foundation · easy

   Which of the following is an example of a real-world QKD implementation?

   • ASatellite-based QKD, such as the Micius satellite, which enables key exchange over long distances.
   • BImplementing QKD on standard Wi-Fi networks.
   • CUsing quantum computers to encrypt data with RSA.
   • DUsing quantum entanglement to create a VPN over the internet.
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5. 14application · medium

   A security analyst is reviewing the security guarantees of QKD. They ask why QKD is considered secure against an eavesdropper with unlimited computational power. What is the correct explanation?

   • AQKD relies on the mathematical difficulty of factoring large numbers, which is computationally infeasible
   • BQKD is secure because the key is never transmitted over any channel
   • CQKD security is based on the laws of quantum mechanics, such as the no-cloning theorem and measurement disturbance
   • DQKD uses one-time pad encryption, which is unbreakable regardless of quantum mechanics
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6. 15application · medium

   During a BB84 QKD session, Alice and Bob compare a subset of their sifted key bits and find an error rate of 2%. What should they do?

   • AApply error correction and privacy amplification to distill a secure key
   • BAbort the key because any error indicates eavesdropping
   • CIncrease the laser intensity to reduce the error rate further
   • DProceed to use the key directly without any further processing
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