Explained: Quantum Computing
Quantum Computer (source)
According to Moore’s Law, the number of transistors in an integrated circuit (IC) doubles approximately every two years. Transistors are semiconductor devices that control the movement of electrons in a circuit. The smaller a transistor is, the higher the number of them can be placed on a specific component, resulting in higher speed and more power-efficient devices. However, there is a limit to how small transistors can become. The smallest functional transistor created to this day is one nanometer (nm) in size. Laws of quantum physics prevent scientists from inventing any smaller transistors because electrons could pass through transistors via quantum tunnelling. Scientists have been researching a new technology named quantum computing that harnesses the laws of quantum mechanics to exponentially increase power. The article is going to explore how quantum computers work, why they are more powerful than classic computers, and how it relates to people around the world.
To begin, computers are devices that allow us to perform tasks more effectively and efficiently. For instance, we produce documents using text editors because digitally typing is more efficient than physically writing and modern text editors provide us with advantageous features such as auto-correction. Text editors allow users to easily modify vocabulary terms, sentences, and paragraph structures to further enhance the reading experience. By writing a document using digital software, people can focus more on significant aspects of the piece such as the content. Similarly, individuals purchase an electric vehicle such as Tesla Model 3 because it is more convenient than traditional automobiles. Tesla provides every user with a charger. Users could then charge their vehicle at home without having to travel a certain range to arrive at a gas station. Additionally, Tesla engineers release software updates that fix bugs and errors in vehicles. Tesla vehicles contain more components common in consumer electronics than they do with other vehicles which indicates that Tesla is taking the same approach to its product similar to Apple. The deep integration of software and hardware in their products allows them to produce more authentic experiences. Technologies similar are examples of computers that allow us to perform tasks more effectively and efficiently but with that said, computers also have limitations.
There are certain tasks that computers cannot perform effectively due to the complexity of input. For instance, “with its one hundred billion neurons and one thousand trillion synapses working in parallel, simulating the human brain would push the limits of even the exascale computers“ [Makin]. One of the biggest challenges that scientists have faced is not being able to simulate the human brain. The amount and complexity of the input is greatly unprecedented that there are no supercomputers powerful enough to process the data. A supercomputer not being able to simulate a human brain is an indication that humanity requires more advanced technologies and many believe that quantum computers might be a solution.
Quantum computers are more powerful than classic computers because they have a component called quantum bits. Binary digits or bits are the smallest units of data in computers that either have the value of 1 or 0. Quantum bits or qubits are quantum versions of bits that store quantum information. “A qubit is a two-level quantum system” [Kurzgesagt - In a Nutshell]. It could be described as 1 and 0. Qubits provide quantum computers with higher processing power because of two special fundamental phenomenons.
Bits could be in the state of either 1 or 0, but qubits in superposition could be in proportions of both states simultaneously. When a coin is on the table, it is considered either face or tail, similar to classic bits. On the contrary, when a coin is spinning, it could be both face and tail, similar to how a qubit could be both 1 and 0 in superposition. For instance, four classic bits could be in two states to the power of four (2^4). It means that there are 16 different combinations, one of which can be used by the computer. A qubit in superposition could be in all 16 configurations simultaneously. As long as a qubit is in superposition, it has the probability to be both 1 and 0. When a qubit is observed, it causes its quantum state to “collapse” either to 1 or 0 and this is when output is produced. Superposition allows for quantum computers to process through many combinations simultaneously but there is another property called entanglement.
When a pair of qubits are entangled, “the two members of a pair exist in a single quantum state” [Giles]. The value of one qubit is changed instantaneously based on the value of another qubit in entanglement. Single qubit values can never be changed independently of another qubit in entanglement. “The quantum state of the system as a whole can be described; it is in a definite state, although the parts of the system are not” [Voorhoede]. To entangle two or more qubits, scientists can bring a group of qubits close together and perform entanglement operations. After that, the qubits could be apart from each other no matter how far, and they will still stay entangled. Entanglement and superposition are fundamental quantum mechanics that allow scientists to create quantum gates.
In classic computers, there are logic gates that perform operations such as addition and multiplication but in quantum computers, there are quantum gates, any set of operations that change the state of a qubit. “A quantum gate manipulates an input of superposition, rotates probabilities, and produces another superposition as its output” [Kurzgesagt - In a Nutshell]. In short, quantum computers work by setting up qubits, manipulating them through quantum gates, and then collapsing the superposition into outputs of either 1s or 0s. Similar to how 4 qubits could be in 16 different configurations simultaneously, a single quantum gate could run many different calculations simultaneously unlike traditional logic gates. Quantum computers are more powerful than classic computers because of the combination of superposition, entanglement, and quantum manipulation but similar to many tools, quantum computers also have many disadvantages.
Decoherence is when the environment around a qubit causes its quantum capabilities to disappear. With the slightest force, change in temperature, variation in radiation, noise, or magnetic attraction, qubits could lose superposition. If balancing a coin is superposition, decoherence is considered the force that collapses the coin. Decoherence is the reason why scientists control quantum computers in “supercooled fridges and vacuum chambers” [Giles]. Decoherence might prevent quantum computers from being used as general-purpose tools since it requires advanced technology to run them.
To conclude, quantum properties such as superposition and entanglement allow quantum computers to compute data at higher speeds than traditional computers. The advantages of quantum computers to the different industries far outweigh the negativity. Quantum supremacy states that quantum computers will be able to compute and solve certain logical problems that would be “demonstrably beyond the reach of even the most powerful supercomputer” [Giles]. Google claims to have achieved quantum supremacy in a calculation done by quantum computers that would have taken an estimation of ten thousand years for classical supercomputers. Based on the evidence, it is clear that quantum computers presumably have and will outperform traditional computers but are they going to replace classical computers? Quantum computers are still expensive devices that are not accessible to the general public. Certain corporations and research firms outsource quantum computers from other companies such as IBM and Rigetti. Only time will tell when quantum computers are going to be available as products for the general public to purchase.