Quantum Computing – Key Discussion Points
At a recent event, I was asked a question on the kind of problems a quantum computer could solve that a classical computer cannot. The audience were also keen to understand why quantum computers were able to do things that classical computers have historically struggled with. A quantum computer could potentially model nature and the complexities that lie within. Classical computers are yet to scale to that extent as bits exist in two states. The ability of quantum systems to exist in superpositions allows them to deal with the problems of exponential. In order to understand how quantum computers can, in effect, leapfrog innovations in several industries, it is critical to understand the fundamental principles of quantum physics that underlie quantum computing.
Many of these principles of quantum physics have evolved over a century, and have a particular weirdness about them, as they are often counter-intuitive to minds...
Superposition
Superposition is one of the properties that differentiates a quantum computer from a classical computer. The qubits of a quantum computer can exist in 0s and 1s and linear combinations of both of these states. A quantum computer can achieve a special kind of superposition that allows for exponentially more logical states at once. This helps in solving problems such as factoring large numbers, which is typically hard for classical computers to solve. Classical computers are limited in terms of their ability to model the number of permutations and combinations that cryptography needs.
An example of the application of quantum computers in cryptography involves RSA encryption. RSA encryption involves two large prime numbers being multiplied to arrive at a larger number. The following examples should bring these challenges to life.
An exponential challenge
The story of the chessboard and rice brings to life the challenges in dealing with the exponential...
Entanglement – spooky action at a distance
The quantum property of entanglement was referred to by Einstein as Spooky action at a distance. Two particles in a system are entangled if one particle in a system cannot be described without taking the other part into consideration. In a quantum computer, qubits demonstrate this property. So, the probability of observing the configuration of one qubit will depend on the probability of observing the configuration of its entangled other half. This property of qubits exists in a quantum system, even when the entangled pair are separated by a good distance. This means, if one qubit spins in a clockwise direction, its entangled pair could spin in a counter-clockwise direction, even when miles apart.
Recently, scientists in China have demonstrated entanglement at a distance of up to 1,200 kilometres. Source: https://phys.org/news/2018-01-real-world-intercontinental-quantum-enabled-micius.html
This experiment was...
Conclusion
In order to understand the interviews in this book, and the key inferences from them, it is essential that this chapter is well understood by the reader. For the same reason, I have described the concepts of quantum computing using practical examples, with comparisons to classical computing equivalents. There are a few concepts of quantum computing that are hard to grasp without delving into the underlying physics (if not the math). In such cases, the simplification of the underlying concepts of physics in this chapter would help understand the weirdness in the behavior of microscopic elements that make up a quantum system. The simplified version may make a quantum scientist cringe, but I firmly believe that simplifying the narrative is critical for any technology to go mainstream.
References
- https://www2.physics.ox.ac.uk/sites/default/files/ErrorCorrectionSteane06.pdf
- https://journals.jps.jp/doi/full/10.7566/JPSJ.88.061009
- https://arxiv.org/pdf/quant-ph/9508027.pdf
- http://science.sciencemag.org/content/356/6343/1140
- https://people.cs.umass.edu/~strubell/doc/quantum_tutorial.pdf
- https://cs.uwaterloo.ca/~watrous/LectureNotes/CPSC519.Winter2006/05.pdf
- https://grove-docs.readthedocs.io/en/latest/vqe.html
- https://quantumexperience.ng.bluemix.net/qx/tutorial?sectionId=beginners-guide&page=004-The_Weird_and_Wonderful_World_of_the_Qubit~2F001-The_Weird_and_Wonderful_World_of_the_Qubit
- https://medium.com/@jonathan_hui/qc-cracking-rsa-with-shors-algorithm-bc22cb7b7767
- https://www.scottaaronson.com/blog/?p=208
- https://quantumexperience.ng.bluemix.net/proxy/tutorial/full-user-guide/004-Quantum_Algorithms/070-Grover's_Algorithm.html
- https://www.cs.cmu.edu/~odonnell/quantum15/lecture04.pdf
