# Quantum Cryptography on Quantum Computing: Questions and Answers

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**Q. 1 What is Quantum?**

**Ans**. “Quantum” is the Latin word for “amount” and, in modern understanding, means the smallest possible discrete unit of any physical property, such as energy or matter.

Quantum came into the latter usage in 1900, when the physicist Max Planck used it in a presentation to the German Physical Society.

**Q. 2 What is Quantum cryptography?**

**Ans**. Quantum cryptography is the science of exploiting __quantum mechanical__ properties to perform __cryptographic__ tasks.

The best-known example of quantum cryptography is __quantum key distribution__ which offers an __information-theoretically secure__ solution to the __key exchange__ problem.

**Q. 3 How did Quantum Cryptography discovered?**

**Ans**. In late 1960՚s Stephen Wiesner from Colambia University and Charles Bennett from Harvard University came together on the Beach of a Posh Hotel at San Jaun, Duerto Rico for the Unforgeable Bank Notes which led the idea of Quantum Cryptography and published a paper named “Conjugate Coding.”

- The Charles Bennett and Giles Brassard had put forward the theory of Quantum Key Distribution by BB84 Protocol both their surname՚s initials in December 1984 at Bangalore which was helped by their best friend Vijay.
- This idea was further carried forward by Artur Ekert which generated the Quantum Key Distribution Protocol with the name BB84 on 1990.

**Q. 4 Why Quantum Computing and Quantum Cryptography?**

Ans. Quantum Computing is the next future of the world which makes the work 100x faster as it simultaneously carries the bits 0 &1 both at the same time in which the guess work is more accurate in comparison with the usual classical computers that are very slow.

- As the technology is growing faster the Quantum Cryptography comes into the picture which makes the security more confidential and very difficult for encryption. Cryptology is divided into cryptography and cryptanalysis.
- Secure quantum communication, i.e.. , quantum key distribution (QKD) , is on the forefront of the commercialization of future quantum technologies. Since its first theoretical proposal, it has been one of the major driving forces to investigate and apply quantum features for future information processing schemes.
- Quantum cryptography, also called quantum encryption, applies principles of quantum mechanics to encrypt messages in a way that it is never read by anyone outside of the intended recipient. It takes advantage of quantum՚s multiple states, coupled with its “no change theory,” which means it cannot be unknowingly interrupted.

**Q. 5 What are the challenges in Quantum Cryptography?**

**Ans**. Quantum cryptography is still in its infancy. But we cannot ignore the challenges it brings to the security of existing cyberspace.

- In 1994, mathematician Shor has proposed the quantum algorithm by which the integer factorization problem and the discrete logarithm problem can be efficiently solved in polynomial time.
*(***Note**:*that so far researchers have not found the classical algorithm to solve the large integer decomposition and the discrete logarithm problem efficiently under the Turing machine model.)* - Therefore, the challenge of the emergence of quantum computers to the traditional cryptosystems cannot be ignored even if it is still in its infancy.