Quantum Cryptography Quiz

What is the key principle that ensures the security of Quantum Key Distribution (QKD)?

• Quantum tunneling

• Quantum entanglement

• Heisenberg's uncertainty principle

• Superposition

Answer explanation

The key principle ensuring the security of Quantum Key Distribution (QKD) is Heisenberg's uncertainty principle. It states that measuring a quantum system disturbs it, allowing detection of eavesdropping, thus securing the key.

What happens in quantum cryptography when an eavesdropper attempts to intercept the transmission?

• The eavesdropper obtains the key without detection

• The quantum states collapse, making the eavesdropping detectable

• The communication speed increases

• The message becomes encrypted more strongly

Answer explanation

In quantum cryptography, if an eavesdropper tries to intercept the transmission, the quantum states collapse. This collapse alerts the communicating parties, making the eavesdropping detectable.

Which quantum phenomenon causes the collapse of a quantum state when it is observed?

• Entanglement

• Superposition

• Measurement

• Tunneling

Answer explanation

The phenomenon that causes the collapse of a quantum state upon observation is known as measurement. When a quantum system is measured, it transitions from a superposition of states to a definite state.

In the context of quantum cryptography, what is "unconditional security"?

• Security based on computational limitations

• Security based on the length of the key

• Security that is not affected by computational resources of an attacker

• Security that expires after a fixed period

Answer explanation

Unconditional security in quantum cryptography means that the security of the system is guaranteed regardless of the computational power of an attacker, making it fundamentally different from security based on computational limitations.

In quantum cryptography, which method can be used to extend the distance over which quantum keys can be distributed?

• Increasing photon intensity

• Quantum repeaters

• Amplifying the quantum signal

• Using fiber-optic cables with larger bandwidth

Answer explanation

Quantum repeaters are essential in quantum cryptography as they enable the extension of key distribution distances by overcoming the limitations of photon loss and decoherence in transmission, unlike the other methods listed.

Practically-speaking, what is the primary limitation of using quantum entanglement in cryptographic applications?

• It requires significant computational resources

• It cannot be achieved with more than two particles

• It is difficult to maintain entanglement over large distances

• It increases the complexity of the encryption algorithm

Answer explanation

The primary limitation of using quantum entanglement in cryptography is that it is difficult to maintain entanglement over large distances, which can hinder secure communication between distant parties.

Which quantum cryptography scheme is most suitable for networks with multiple users requiring shared encryption keys?

• E91 protocol

• BB84 protocol

• RSA encryption

• Quantum Digital Signatures (QDS)

Answer explanation

Quantum Digital Signatures (QDS) are designed for multiple users, allowing them to securely share encryption keys. In contrast, BB84 and E91 are primarily for point-to-point communication, while RSA is not a quantum scheme.

In quantum cryptography, what is "quantum bit error rate" (QBER) used to measure?

• The frequency of errors in classical encryption keys

• The noise in a quantum channel

• The computational resources needed to correct errors in classical cryptography

• The rate at which quantum states are affected by environmental factors

Answer explanation

Quantum bit error rate (QBER) measures the noise in a quantum channel, indicating how much the quantum states are disturbed during transmission. This is crucial for assessing the security of quantum cryptographic systems.

How does the concept of "quantum no-cloning" contribute to the security of quantum cryptography?

• It ensures that quantum keys can be perfectly copied

• It prevents an eavesdropper from duplicating an unknown quantum state

• It allows for faster distribution of quantum keys

• It enhances the transmission rate of quantum data

Answer explanation

The concept of 'quantum no-cloning' ensures that an eavesdropper cannot duplicate an unknown quantum state, which is crucial for maintaining the security of quantum cryptography.

What is the role of "quantum randomness" in quantum cryptography?

• It ensures that encryption keys are unpredictable

• It stabilizes quantum entanglement between particles

• It reduces the error rate in quantum channels

• It allows faster transmission of quantum data

Answer explanation

Quantum randomness is crucial in quantum cryptography as it ensures that encryption keys are unpredictable, making it extremely difficult for eavesdroppers to decipher the information, thus enhancing security.