By Harrison York
Every once in a while we hear news of a new breakthrough in quantum computing technology and excitement builds in anticipation of these developments. Experts talk about the possibility of quantum computing, and it sounds fantastical. Yet, despite these breakthroughs, quantum computing still seems far away and mysterious. But what exactly is quantum computing? What should we be excited about? And when can we expect it to actually change our lives?
First, it is important to understand that quantum computers (like the ones you hear about online) and classical computers (like the one you are reading this on), are both called computers, they are very different. Each one has advantages over the other, and because quantum computers are so new, there are many technical difficulties that have to be worked out before they become a viable option for companies and institutes to use. That being said, quantum computing has the potential to solve huge, complex problems that classical computers are simply unable to.
Quantum computers, as the name implies, use the science behind quantum phenomena to solve complex tasks more quickly than regular computers. Quantum phenomena are processes that occur in matter on an extremely small scale, and many of these processes look very different from the physics we observe in the world around us. Quantum mechanics, the scientific study of these micro-events, work to explain the interactions between individual atoms and their subatomic particles. But quantum mechanics is still a new field and there is much to be discovered. And even the discoveries that have been made are not yet fully understood.
In order to make computations, quantum computers manipulate qubits, or quantum bits. In classical computers, “bits” store information in a binary, as a 0 or 1. So each “bit” represents one tiny piece of information, either a 1 or a 0. When combined bits allow us to store and use long strings of information. Qubits, like bits, can also be 0 or 1. But on top of that, a single qubit can represent many different combinations of 1’s and 0’s at the same time, making the potential of a qubit much more than that of a classical bit, as it can contain more or different types of information (Martin Giles / MIT). This is due to the quantum-mechanical property of superposition, which means that at all times there is probability that a qubit is either a 0 or 1, and is essentially both at any given time. The state of the qubit is unknown until it is measured. When the qubit is measured, the probabilities collapse into a definite binary result and the qubit is defined as a 1 or a 0.
With the presence of both a 1 and a 0, qubits can process many possible outcomes at the same time. Thus, when many qubits are used in a quantum system, its processing power scales exponentially. Where a classical computer can process information related to the number of bits, an ideal quantum computer would be able to process information on a scale of 2 to the power of the number of qubits. Today, however, it is difficult to gather and manipulate large numbers of qubits due to their physical properties, like size and fragility. But larger numbers of qubits reduce the error rate of quantum systems, which is an inevitable issue in quantum physics caused by the finicky physics relied upon to make these computers function.
One problem of quantum computing is isolating and controlling these qubits. IBM and Google use special circuits cooled to extremely cold temperatures to do this while another company, IonQ, traps atoms in electromagnetic fields in vacuum chambers. Qubits behave very differently from bits as a result of the quantum properties employed in these computers. The two main properties utilized are superposition (as discussed above) and entanglement.
Entanglement is another strange concept. In this process, pairs of qubits can become entangled and exist in the same quantum state (1, 0, or a superposition of the two) at the same time. When one qubit of the pair is manipulated or changed, the other qubit will instantly and predictably change to match its partner. This happens even over long distances, and why it occurs confuses just about everyone. Einstein called it “spooky interaction at a distance,” and there are still limitations on how the process can be used to communicate information. Although difficult to harness, entanglement is necessary to create a capable quantum machine that measures every qubit to collapse the superposition of answers down to a definite solution.
The enemy of the processes of superposition and entanglement is called decoherence. It is the decay of qubits over time and is caused by interactions with the outside environment that interfere with the balance of a quantum computer. Slight vibrations and changes in temperature, generally referred to as “noise” by quantum scientists, are detrimental to quantum computing. Overcoming such disturbances is the greatest challenge in making this technology successful and practical. As a result, quantum computers have complex cooling and protective systems that reduce “noise.” A cooling apparatus serves to slow the motion of qubits and keep them in a stable state so they can be maintained and measured for a period of time.
Still, despite the intricate challenges, researchers, scientists, and engineers keep pushing forward towards “quantum supremacy.” Quantum supremacy is the point at which quantum computers can demonstrate their ability to solve problems beyond the most powerful classical computers. Progress is steady as leaders in the field are finding new ways to optimize the performance of current machines and build ones with more qubits and processing capabilities.
“Quantum computers will find a use anywhere where there’s a large, uncertain complicated system that needs to be simulated,” (Amit Katwala / WIRED).
Quantum computing is already being applied in various fields. One major use is modeling complex chemical structures. Auto manufacturers do this when analyzing the chemical composition of batteries in electric vehicles. At IBM, researchers are modeling caffeine and other substances in hopes of discovering new materials and possibly new medicines. Pharmaceutical companies are similarly analyzing compounds with quantum technology.
Cryptography is also an interesting area that quantum computing will affect. Encryption systems currently rely on breaking massive numbers into prime numbers. For classical computers, this is slow and expensive to do. Quantum computers, however, may be able to break these codes with ease. This would put most of today’s data at risk, as our cyber security measures would be unable to withstand the capabilities of quantum computers.
The solution to this problem is, in fact, a new kind of encryption based on the uncertainty principle of quantum mechanics. This principle states that nothing can be measured without the result being affected. On a small, quantum scale, this is significant, and quantum encryptions can be designed to prevent both classical and quantum computers from being able to crack keys that protect data.
Deeper than chemistry, quantum computers may one day have the ability to simulate quantum systems, such as models of organic chemicals or other complex data. This will help researchers get a better grip on the processes still confusing the industry and open up this mysterious micro-world to scientific eyes. These simulations are too complex for today’s supercomputers, taking too much time and money to be worth it to process.
Besides these large problems, though, classical computers will still reign on the consumer level. Quantum computers, as we understand them, will not be practical for use as a phone or laptop because of their delicateness and technical requirements. In the past, science has overcome significant hurdles of doubt, but in order to properly understand quantum computing, it is important not to get carried away by unlikely possibilities, especially in the near future. Quantum computers are still only being developed for laboratory use.
But perhaps the greatest use of quantum computers has not yet been imagined. Lasers, for example, play a role in some quantum systems by isolating qubits. But lasers were originally never thought to have applications in things like CD players, grocery store scanners, or as Christmas decorations, and yet these devices are used both in labs and in homes. Perhaps the most important use for quantum computers will become as commonplace as the laser is now. As the technology develops, its capabilities will surely expand and reach new areas, changing our world in innumerable ways.
1. What are the processes that quantum computers use that set them apart from classical computers?
Qubits are the quantum counterpart to classical computers’ bits. They use the quantum properties of superposition and entanglement to communicate information and be manipulated by these systems. Superposition gives them the ability to behave as a combination of the two final states of 0 or 1, resulting in exponential computing power the more qubits can be used (reliably) in a system. Entanglement ties two qubits together, changing the pair when each single qubit is manipulated individually. The two processes have their problems, but work is being done to overcome them and make quantum computers practical.
2. When will quantum computers become a reality?
Quantum computers are already being used today by technology companies for research and problem-solving. They are still sensitive to “noise” from the environment, and the challenge of keeping qubits isolated limits the number that can currently be used in systems.
No changes were made to the following image, IBM | IBM logo on RS6000 machine | Kansir | Flickr, License: Creative Commons Legal Code