# Quantum Computing Explained

Quantum computing has been a speculative subject that was originally developed as just an idea. More commonly known as an area belonging to quantum mechanics, quantum computing is really a promising fusion of concepts from physics, mathematics and computer science. Why promising? Let's find out.

Preeti Sunil

Last Updated: Jun 3, 2018

**Making Sense of the Word "Quantum"**

In order to have quantum computing explained, we need to delve a little into quantum mechanics. Quantum mechanics is based on the principle that every object is made of quantum particles or quanta (atoms, electrons and photons). These particles, sometimes, behave as waves and sometimes the waves behave as particles, but really they are neither, unless someone observes it. In addition, what the observer finds is well, a random probability! Sounds bizarre? Well, hang in there. The quanta can exist in the two states simultaneously! This is called the

*superposition*principle in quantum theory which finds application in quantum computing. Another counter-intuitive quantum principle states that there exists a strong correlation between quanta even when they're separated by vast distances, even if they're at opposite ends of the universe! This is the

*entanglement*principle. Welcome to the quirky world of quantum mechanics.

**How do Quantum Computers Work?**

If the above paragraph didn't make much sense, perhaps this one will. A classical computer uses bits to encode information, representing either one or zero, while a quantum computer uses qubits. So with reference to the above paragraph, a qubit can represent a one, a zero or a superposition of these simultaneously, thus achieving

*quantum parallelism*. From this, we understand that a qubit can essentially represent significantly more information than a bit in a classical computer.

Quantum computing began as an idea that if the principles of quantum mechanics could be represented by building a quantum computer, computing could be revolutionized. Richard Feynman, a Nobel prize winning physicist is considered one of the pioneers in the field of quantum computing. He thought up the idea of a quantum computer in 1982. In 1994, Peter Shor, a scientist with Bell Labs, devised an algorithm that could be used to factor huge numbers especially products of prime factors, using a quantum computer. However, this was again a theoretical attempt as there was no actual quantum computer built to test the algorithm.

**Early Challenges in Building a Quantum Computer**

Although quantum computers have since been built, especially in the last few years, the pioneers in this field had some real challenges in attempting to build them. While several algorithms were written for a hypothetical quantum computer, the counter-intuitive principles on which it was based ironically posed the biggest challenge in realizing an actual physical device. Maintaining the coherence of the quantum states proved to be most difficult. Quantum parallelism could be achieved only when the quantum states could be preserved/controlled for a certain desired duration. External environmental factors (including the act of measuring a quantum state, classical noise and quantum noise, etc.) were known to cause

*quantum decoherence*and all subsequent research in the field of quantum computers began focusing on controlling or removing decoherence by isolating these external factors.

**Devices to Control Quantum Decoherence**

*Ion Traps and Optical Traps*: Elongated electrodes form an electromagnetic field to trap ions, curbing the potential for the atoms to swerve. Ion trap devices have also been fabricated on chips. Optical traps apply light waves to control particles.*Superconducting Qubits*: These allow electrons to flow with least resistance at low temperatures.*Semiconductor Qubits and Quantum Dots*: These possess long coherent times.

**Have Quantum Computers Been Built?**

Quantum computers with a few qubits (up to 10) have been built in research labs and they do perform some basic mathematical computations. One of the most inventive companies of the world, IBM is investing in quantum computing research because they foresee great market potential. Many other companies as also computer scientists believe that once quantum computers leap forth from research labs into commercial territory, they could become game changers. A fully functional quantum device with thousands of entangled qubits is still a futuristic idea. However, there's much less speculation in the capabilities of quantum computers. In fact, many scientists agree that an actual full-scale powerful device could well open up possibilities that have not been imagined or perceived with the current toy models, simulation algorithms and theories.

**Is it Already in the Commercial Market?**

If you thought the world of quantum computing is bizarre enough, here's something that's on the same lines. In May 2011, a Canadian company called D-wave Systems was in the news for having sold a 128-qubit quantum computing system, called "D-Wave One", to a global security company, Lockheed Martin. While some researchers have questioned the company's claims of having built a mythical system known to exist only theoretically, however, the company is moving ahead with building even more powerful quantum computers by scaling up to thousands of qubits. Lockheed Martin being a security company, all design aspects and applications of its state-of-the-art purchase have been kept a secret, further fueling speculation.

**Uses of Quantum Computers**

Quantum computers were always thought of in the context of complex mathematical computations and aspects such as machine learning and artificial intelligence. Quantum computing promises to have the capacity to simultaneously compare a huge number of variables and working out a huge number of probabilities. These attributes make it ideal for application in the following area.

*Medical Diagnosis*: In this case, several symptoms will need to be compared with several disease characteristics and the results of several other diagnostic tests.*Bioinformatics/Biomedical Simulations*: The parallel processing power of quantum computers will be helpful in comparing huge clinical data sets with statistical and probabilistic tools.*Robotics*: Machine learning and artificial intelligence concepts can utilize the power of quantum computers to power the brains of intelligent robots.*Climate Modeling*: Again due to the capacity to perform parallel processing of a range of variables, quantum computers can provide hi-tech simulations.*Cryptanalysis*: Circumventing security encryption by cracking ciphers to expose weaknesses in the security systems, this technique involves working with various combination of secure keys which is a trademark use for quantum computers.