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Written by: Xiaoyu Huang
Written on: April 30th, 2014
Tags: electrical engineering, physics
Thumbnail by: Torah Kachur/Science In Seconds
About the Author
Xiaoyu Huang is a junior majoring in electrical engineering and minoring in cinematic arts at USC. He enjoys discovering fun gadgets and new technologies that involve electrical engineering.
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Volume XVII Issue I > Encrypt the Future – Quantum Cryptography
The inherent weakness of traditional cryptography has exposed its unreliability to modern computing technology. To overcome this issue, scientists used the laws of quantum mechanics to create quantum cryptography, which is invincible to conventional hacking. By developing the quantum cryptography system, conventional hacking will eventually be eliminated.


The internet, as one of the greatest inventions in the world, has served many functions in our society. Without the internet, people will not be able to communicate freely with each other, and more importantly, the internet connects everything together to create the ultimate digital world – a place where everything is expressed as zeros and ones. The internet is composed of various data such as personal information, online banking data, private records, and even confidential government data. It is essential that the sensitive information can be protected so that unauthorized people cannot access the data. Fortunately, we have the solution of modern cryptography, which is the digital safe protecting massive amount of data that is being accessed by millions of people daily. However, as scientists discover more and more about advanced computing technology, the inherent weakness of traditional cryptography exposes its unreliability to modern computing technology. Nowadays, we are at the calm before the storm of confidentiality crisis because evidence has shown that the crisis in confidentiality is approaching us.

Confidentiality: Crisis of Traditional Encryption

Because of the unreliability of traditional cryptography, scientists are searching for a way to replace the traditional cryptography, a solution that is invincible to be hacked. In the traditional encryption, information can be encrypted and decrypted using a unique secret key – a mathematical algorithm that could overwhelm the current computing ability. However, emerging technologies have spawned new computers that possess more powerful computing ability, such as quantum computers. In January 2014, The Washington Post published an article revealing that the National Security Agency (NSA) is racing to build a quantum computer that could break nearly every kind of encryption used to protect banking, business, and government records around the world [1]. Moreover, according to Yahoo! NEWS, China is also working on building a quantum computer to rival the one being constructed by the NSA [2]. Once the quantum computer is built, it will be capable of performing the most complex calculations in a relatively short amount of time, which will also put 99.9% of private information and financial transactions at risk of being hacked [2]. In order to prevent valuable information from being hacked by quantum computers, scientists need to find a new encryption method that does not depend on mathematical algorithms. After years of research, scientists have begun to consider quantum cryptography as a replacement for traditional cryptography because of its unique advantages in quantum mechanics.
Enter the Quantum World
What is a small object? Different people may give different answers based on their personal experiences – a pen is small, a needle is smaller, and the dust is even smaller! However, when zooming into the quantum world, scientists find a place on a much smaller scale than anything that can be seen by human eyes – a place that is dominated by atoms. Comparing to normal world, atoms are unimaginably small, and the normal physical rules in the microscope world will behave in a totally different way in the quantum level [3]. Considering the example of classic projectile motion, people know that particles move in a trajectory that obeys Newton’s laws of motion. In order to observe the motion of a particle, we see the reflection of the light to locate the position of the particle and then draw a relationship between time and position. However, it is very hard to observe particles in the quantum world since electrons possess both particle and wave properties, and the collision of an electron with a photon will actually change an electron’s motion; in other words, we cannot simultaneously know the position and velocity of an electron, which means we cannot obtain the exact trajectory of an electron [3]. Therefore, in quantum mechanics, traditional trajectories are replaced with probability distribution maps, as shown in Fig. 1 [3].
Tro, Nivaldo J/Pearson Education
Figure 1: Trajectory vs. Probability, the dots indicate the possible position of the electron.
It is a fact that an atom is composed by the neutrons and protons within a nucleus and electrons that orbit around that nucleus. Since atoms are always in motion, scientists use quantum numbers to specify the orientation of the orbital – the spinning motion of the particle [3]. Although quantum numbers could be found arbitrarily, the relationship between each quantum number will always follow the rules of quantum mechanics. After years of studying on quantum mechanics, scientists were able to use the uncertainty of quantum particles to make quantum cryptography – an encryption method that is free of mathematical algorithms; that is to say, quantum cryptography is invincible to hacking, not even quantum computers could decrypt quantum cryptography.