Quantum Computers: The Solution To Our Computing Problems?
Large organizations like Google, IBM, and the US government are investing heavily in quantum computing. Why?
The computer known as Sycamore was shown to solve a highly complex math problem in around 200 seconds, or 3 minutes and 20 seconds. Why is this significant? Well, Google claimed that a modern state-of-the-art supercomputer would have taken 10,000 years to solve that same problem. The reason for this substantial increase in computing time: quantum computing. Sycamore is a quantum computer that uses quantum mechanics to substantially increase its computing power.
After tossing around the word ‘quantum’ so many times, we need to answer several questions. What exactly is a quantum computer, how does it work, will it solve all of our problems, and will it sit on your desk in 100 years? Let’s explore!
Qubits
The primary difference between normal computers and quantum computers can be summed up by one word: qubits. While normal computers, like the Mac or Windows computer on your desk, run using a binary system, quantum computers use quantum bits, or qubits. The binary system is the string of 1s and 0s that you may have heard about, where each 0 or 1 is a ‘bit’. In a normal computer, sequences of bits are sent in electrical or optical (light) pulses. Virtually every single app, program, website, or streaming service uses this binary system.
How do qubits differ from bits used in the binary system? First, we need to understand the fundamentals of a qubit. Qubits, instead of using electrical and optical signals, use subatomic particles, such as electrons or photons. The qubit’s superiority comes from the fact that instead of representing 1 or 0, as bits do, a qubit can represent both at the same time. The reason for this lies in something known as superposition, which we will look at later in the article.
To understand this, we need to see that qubits show both 1 and 0 using levels. A qubit has two levels (for 0 and 1), a qutrit has three levels, and a qudit is anything with more than two levels. Each level is essentially shown through the motion of a subatomic particle. If an atom is rotating one way, it can represent a 1; if it rotates the other way, it can represent a 0. Now, imagine that same atom rotating diagonally or at a different angle. Using such motion, qudits can represent more information than regular bits.
Superposition
Remember when I mentioned the term ‘superposition’ earlier? Let’s break it down. Superposition, in simple terms, is when a qubit represents 1 and 0 simultaneously.
The superposition of qubits is crucial to quantum computing. The superposition of said qubits is controlled using a laser or beams of microwaves. No, the microwave used isn’t the machine used to heat your leftovers; instead, it is a specific frequency of waves like radio waves. Having a qubit in superposition means that it can transfer and analyze vast quantities of information in an instant. This is why the quantum computer solved the math problem mentioned earlier in 3 minutes and 20 seconds instead of 10,000 years like a normal supercomputer.
Quantum Mechanics
Quantum computers often use fundamentals from quantum mechanics, which deals with the behavior of atoms and their building blocks. To paint a quick picture of the truly fascinating laws in quantum mechanics, imagine a tennis ball. Now, imagine throwing that tennis ball against a wall. What happens? Obviously, it will bounce back — that's not a trick question. What’s interesting, however, is that if the same tennis ball was the size of an electron, it would go right through the wall. This relies on the principle that extremely small objects can have the properties of waves and particles. This effect of objects going through each other is known as quantum tunneling, and it is interesting yet troublesome.
If you remember, quantum computers often use electrons and photons, both of which are subatomic particles. This means that these electrons and photons have a high probability of encountering quantum tunneling. Imagine you are an electron on your daily commute through a circuit. Suddenly, you just fall through the circuit and can’t go to work. This is the issue with quantum tunneling: the electrons in the string of code can simply go away, which causes problems in the quantum computer. This issue is even visible in modern devices like your cellphone. As the components of your phone (e.g. processor) continue to get smaller, so does the energy zipping around inside. This means that the particles in your phone will soon be subject to the same issue.
How do engineers solve such problems? Well, there are currently two different methods. One method is to use a superconducting circuit that is frozen to around 0 Kelvins. This is around -273 degrees Celsius or -459.4 degrees Fahrenheit. For reference, the coldest element on the planet, liquid helium, is around 4.2 Kelvin, and the coldest naturally occurring place currently known in the universe is the Bow Tie Nebula, with a temperature of approximately 1 Kelvin. The second method used to avoid quantum tunneling is by trapping each atom in an electromagnetic field and then placing them in a silicone chip in a vacuum chamber. Both methods are used to help control the state of the qubit.
Entanglement
Entanglement is about as sci-fi as quantum computers get. It generally refers to when two qubits remain in the same position as each other. When one qubit changes from, say, a 1 to a 0, the other qubit will do the same instantaneously. Now, imagine one qubit in Australia and the other qubit at the center of our galaxy. Both qubits remain “connected” and they will still change positions in regards to each other, even though they are far away from each other.
Currently, scientists do not completely understand entanglement, Einstein even went as far as to say it was a “spooky action at a distance”. Entanglement is used in quantum computers to increase the processing power of the quantum computer. The more qubits in the quantum computer, the higher the processing power. This same principle is found in normal computers as well. Quantum computers are often categorized on how many qubits that they each have. For reference, the Sycamore had 53 qubits and was shown to have achieved “Quantum Supremacy”, which is attained when a quantum computer completes a task in less time than a typical computer that needs an unfeasible amount of time to solve the same task (10,000 years seems unfeasible to me). “Quantum Supremacy” is heavily debated, and the exact requirements (or measurement of the computer) for reaching the supposed “Quantum Supremacy” are still undecided.
Decoherence
So far, we have discussed all of the things that make a quantum computer ‘quantum’, but we have not talked about the setbacks of these powerful machines. One such flaw is that they have to be kept at freezing temperatures and/or vacuum chambers, and the slightest change in temperature or vibration can render a quantum computer useless. These disturbances are called “noises” and are one of the main limiting factors of quantum computers. When such disturbances occur, the quantum state of the qubit can be lost in a process known as decoherence.
Nowadays, almost all of our efforts to prevent “noise” are rendered useless because eventually, some noise will creep in. This makes calculations and analytical information from a quantum computer prone to error. Thus comes the variation in qubits from standard to logical. To stop decoherence, scientists may add more regular qubits, but to create one reliable qubit with more “resistance” to decoherence, it takes thousands of such standard qubits. When these many qubits are compiled, they form a logical qubit.
Decoherence is the main limiting factor to quantum computers, and at the moment, we have a long way to go if we want to create a reliable and accurate quantum computer. This doesn’t mean that quantum computers are useless, but it does mean that having a quantum computer on your desk is probably not going to happen anytime soon. This is because present-day quantum computers are behemoths with lots of requirements.
Power And Impact Of Quantum Computers
We now know what quantum computers are and why they’re so powerful, but where is this power going to be used? Well, we already know that having a quantum computer replace a normal computer is unlikely. While the first normal computers like the ENIAC would take up entire rooms and programming them was difficult, they were downsized into the laptops and desktops you have. The quantum computer, on the other hand, costs much more, and for video editing, programming, school work, or any other task on your computer, a quantum computer would be overkill. Think about it like this: instead of biking over to a neighbor’s house 2 minutes away, you decide to ride a spacecraft to the house — regular tasks don’t need that much power.
So what is the purpose of quantum computers? One thing to clear up is that different types of quantum computers have different purposes. Such computers include the Quantum Annealer, Analog Quantum, and Universal Quantum, from least powerful to most powerful respectively.
The main benefit of quantum is power. Look at the novel coronavirus: it took about a year to analyze the different compounds of the virus and perform calculations to find a vaccine for COVID-19. The same task could be done by a quantum computer in a fraction of the time. This isn’t possible today, though, due to all the limitations of quantum computers like decoherence.
Outside of vaccines and drugs, other technologies could be improved using quantum computers. For example, modern batteries are commonly made out of lithium-ion due to its chemical properties. However, we are at a standstill with battery technology. Some claim to have found more powerful batteries using materials like sodium-ion or lithium-sulfur. These new batteries still require testing to support these claims, however. A quantum computer could run millions of simulations on different compounds to find the most ideal battery material.
There are many more uses for quantum computers such as performing virtual experiments, crunching large numbers and analytics, paving the way for innovations, and more. While the modern quantum computer can not do this yet, the future looks promising. Most of us will not see or operate a quantum computer, but the future is never set in stone — innovation never sleeps!
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