Quantum Computing 101
With our vast knowledge of this world, for some reason we continue to think that anything is possible. Thanks to this stubborn human quality, we have pioneered and engineered time after time a “better” and “more efficient” method to improve our lives and solve our problems. This time might be a little different, this time the upgrade might be a lot more than we have ever seen before. For many years, we have been researching, studying and programming an unstoppable machine, that is capable of processing more data than our fellow human beings could ever imagine. Thus, it is capable to simulate breakthrough experiments that we have never been able to do before and even solve some computational problems that even if all the computers in the world were put together to solve the problem for hundreds of years they would have no chance to solve them, this solution is quantum computers.
How Does It Work?
But seriously, what are quantum computers and how is it unique to anything we have created over the millennia that humans have roamed the earth?
Well, quantum computers are technologically advanced machines able to use qubits and the counter intuitive laws of quantum physics such as superposition and entanglement to process large amounts of data in order to do some extraordinary things, but first let’s break it down.
Law of Superposition
First of all, let’s start with what the difference between a quantum computer and a classical computer is. The main difference between these two types of computing devices is that they have different forms of storage for their information. Classical computers have something called a bit, which are like a switch for “on” or “off”, “yes” or “no”, “true” or “false”, but we will stick to the easiest representation, 0 and 1. On the contrary, quantum computers have a qubit which is a lot smaller, and therefore follows the laws of quantum physics instead of normal physics? The qubit’s ability to take advantage of certain quantum qualities is what allows quantum computers to do so much. Instead of just being in an energy state of 0 or 1, they have the ability to take advantage of the first major law of quantum physics superposition, and occupy a state of both 0 and 1. This unique quality allows a computer to conduct calculations in parallel to perform 2^n calculations in one unit of time where n is the number of available qubits instead of the usual n calculations it could perform if n was the number of available bits. Using this principle, a quantum computer only needs 3 qubits in order to hold as much information as 8 regular bits. This is one reason why quantum computers are superior to our current classical computers.
Now you might be wondering, how does one obtain one of these powerful qubits? Any object able to obtain superposition can be a qubit. This includes the atomic nucleus, atoms, ions, photons and even individual electrons. Generally they are objects small enough that they follow the laws of quantum physics.
Law of Entanglement
Another vital property that qubits possess that gives quantum computing its advantage, is the law of entanglement. This law allows users to make more complex calculations using qubits. With the use of radio waves and other types of signals used to influence qubits, it is possible to make one qubit act relatively to another. Depending on the type of link created between the qubits, you are able to make the pair of qubits inversely related to each other or directly related to each other. One approach to use this law is: if one qubit turns out to be measured as a 1, you are able to make the other related qubit equate to that same value or the opposite (i.e. a 0). This is an important quality, especially used as a tool within quantum gates which allows programmers to develop more complex algorithms. One of the most effective uses of entanglement is within the field of information security for future quantum encryption which is for another article.
Types of Quantum Computers
As seen on the infographic on the left, there are three main forms of quantum computers that we have been able to categorize machines into, the quantum annealer, the analog quantum machine and the universal quantum machine. Currently, we have some innovative and successful companies such as D-wave creating working quantum annealers with 2000 qubits. There was debate for whether or not this was even considered a quantum computer since it had very limited applicationss, but nonetheless D-wave has created the world’s largest quantum annealer. A couple applications for quantum annealers include solving optimization problems, combinatorial problems, and sampling problems using the properties of superposition, entanglement and another property called quantum tunneling. With these types of problems, the quantum annealers show a greater efficiency, as reported by google, they are more than 1⁰⁸ times faster than simulated annealing running on a single core. On the other hand, for most other applications it may not even operate at par or even sub par relative to classical computers.
The next generation of quantum computers that the industry is hoping to develop is specifically called the gate model quantum computer. As you would expect, this is a much harder type of computer to achieve because of the difficulty to wield the qubits. With this new method, we must keep the qubit in a state of coherence in order to maintain information storage. This type of quantum computer is able to push through many of the limitations of our previous quantum hardware and is even able to potentially run the infamous algorithm that has put this technology into the social spotlight, Shor’s algorithm, which is infamous since it breaks RSA cryptography. So far, the furthest we have come to a gate based quantum computer is the 72-qubit gate based quantum processor that Google created which still has a ways to go in terms of development and reliability.
Another cutting edge company innovating in the quantum computing space is Rigetti. Rigetti is currently developing an abstract hybrid quantum computer which has the power to use the functionality of both classical computer components and quantum components in order to help with compilation and many other processes. In these types of computers, the quantum components are only used if it would be able to complete a task more efficiently or quickly than its classical counterpart. One aspect of this process that Rigetti is working on is the transition between the use of either type of processor. The current goal for Rigetti is to make a 128-qubit chip which will allow for one of the strongest and most efficient quantum computers today. Some of their product’s applications include: quantum simulations, optimization, and machine learning which is more than what the annealers could accomplish.
Current Obstacles
The limited ability of quantum annealers have made us determined and focused on creating a more powerful quantum chips that are able to run the increasingly popular algorithms and simulate important scientific experiments on. Through the industry’s journey in creating the all power quantum computers we all desire, they have had to deal with 2 huge problems: error detection/correction and decoherence. These problems are quite related but separate in their own ways.
Errors occur in quantum systems because of fragile qubits and their inability to be stable in a state of superposition. It is quite easy to disturb them, thus resulting in inaccuracy and misinformation being sent to the user. An algorithm created by Peter Shor helped to deal with this problem, he explains a concept called Quantum Error Correction where entangled qubits help detect each other of errors and correct them which in turn keeps the qubit intact for longer and results in more accurate calculations.
Among qubits, it is very difficult to keep qubits in a state of coherence because of how easy it is to jeopardize it. By exposure to radiation, light, sound, vibrations, heat, magnetic fields or even the act of measuring a qubit could result in a disruption of quantum information processing. Even though some of the current quantum processes are carried out more efficiently and faster than the classical approach, I believe we must overcome these problems before we are completely confident of quantum supremacy.
TLDR
Quantum computers are the next generation of computing and there are many different types being created and improved on. Some startups such as D-wave are creating quantum annealers and another called Rigetti is creating another type called hybrid quantum computers. These types of computers are able to outperform classical computers in some specialized tasks using special quantum properties called superposition, entanglement and tunneling. We currently also have many problems slowing our continued progress that we must solve in order to achieve true quantum supremacy.
