Quantum Computing is the next evolution of Computers. If Commercialized, they can single-handedly nullify modern day encryption and change how we use computers.
The reason why we are looking into Quantum Computing is because we are reaching physical limits to the size of processors. Understanding how processors work, small mechanical items called transistors have an on and off state, either letting electrons pass through or not. These 2 states are represented as '1' for electrons passing through and a '0' for electrons not passing through. This is the basis of binary representation (number system for representing numbers with a series of 1 and 0) and gives the computer the power to understand numbers and math properties (adding, multiplication, etc.). Here is a reference to how binary numbers work.
Due to increased demand in processing power/speed in everyday computers, transistors have become smaller and smaller so the computer can have more transistors, effectively increasing the number of functions it can compute simultaneously. The physical barrier being reach is the current size of transistors. Typically, transistors are 14nm (nanometer) small. For perspective, a virus is normally 100nm small, and the smallest human cell is 30,000nm small.
The complication of atomically small transistors is the possibility that electrons may pass through whether or not the state is on or off (in a quantum process called quantum tunneling). Quantum Computing looks to be the next step after processing speeds stall from physical complications.
The idea of a quantum computer is using the quantum properties of sub-atomic molecules to create a computer. A quantum computer hypothetically uses a quantum bit, or a qubit, that can be both 1 and 0 at the same time. When the qubit is read, there’s an always-evolving probability of it being 1 or 0. This is referred to as a superposition, where each qubit is effectively 1 and 0. a physical example is the polarization of a photon: it can be polarized horizontally and vertically, but in a filter, it will choose (collapse into) one polarized state. Looking at a regular byte (8 bits), Each bit is definitely 1 or 0, so there are 256 different ways to represent 8 bits. In a quantum computer, a single qubyte (8 qubits) can represent all 256 possibilities through it’s superposition. If one were to represent all numbers from 1 to 2100 using bits, they would need to use 2100 bits to represent each individual number. If one were to use qubits, they would need only 100 qubits because 100 qubits can be 2100 different numbers. This is big for differentiating a regular computer to a quantum computer's: Qubytes performing a process become exponentially faster compared to a regular computer using bytes.
Although the hypothetical advancement of processing power looks to be promising and allow us to ‘simulate the universe’, there are major downsides to a quantum computer. Simplified, Modern day encryption uses a large prime number (so that it can’t be broken down) multiplied by another prime number to create a ciphering key, that will replace letters and symbols with numbers in bit format. Encryption makes data secure because the key only one computer has the key to a given encrypted data. For an outside computer, deciphering what the key is means it has to look at every single possibility of the 2 numbers in a sequential fashion. This process would take thousands of years to compute. However, if a quantum computer were to try to solve an encrypted key, it would take minutes. The power of a quantum computer can be undermined unless we look at practical examples: a quantum computer can brute force solve encryption millions and millions of times faster than a regular computer. The reason encryption works is because a computer can’t simply process what the encryption key is (guessing effectively is the only way hackers/Engineers break encryption). Now with Quantum Computing, all encryption can be hypothetically nullified and ineffective, making all data accessible by anyone.
Fortunately, there’s a quantum solution. In another quantum process called quantum entanglement, a qubit can be entangled to another qubit, where when one collapses to 1 or 0, the other immediately collapses to the opposite, regardless of their distance apart. Before talking about that importance, let’s talk about the superposition of a photon’s polarization, again. Using the superposition of a photon’s polarization, a computer can hypothetically make a key randomly made by qubits to encrypt data. Now if the qubits in an encryption key are quantumly entangled, that means that if one qubit is viewed by an outside computer, the entire key will be entangled differently based on the superposition of the one qubit, making the data useless. When the encrypted key reaches the recipient, it will use 2 detectors for the state of 1 and 0 so that each photon can collapse to 1 or 0. Based on the qubits that had the same superposition in the original key and the recipient (verified by the computer who made the key), a deciphering key will be generated. Beyond how encryption keys can be verified or work effectively, the big thing is that the quantum property of entanglement makes it practically impossible for an outside computer to intercept data, for merely attempting to copy the data would completely change the data. If one attempted to view the encrypted information, the recipient would immediately know by the entanglement. This, referred to as quantum cryptography, is a type of protection of data that has never been seen before, and may very well be fundamentally unbreakable. If this were to be implemented, cyber security would become a lot safer, regardless of the computational power of an infringing outside computer.
Of course both Quantum Computer and Quantum Cryptography have long ways to go. For one, Quantum Computers have to be put in chambers with a temperature nearly at the absolute zero due to excessive heating. As for Quantum Cryptography, Practically anything can change the polarization of a photon like slight changes in temperature or a 1-degree rotation, making it really unreliable for encrypting messages. But we are making progress. Google and NASA partnered with D-Wave to create a quantum computer 100 million times faster than a regular computer. Optical Society Researchers developed a 200nm cavity that can detect photon superpositions more securely. Quantum Mechanics can happen, and eventually it will happen. As long as we are aware of the changes that will come, Quantum Computers can really change how we use computers forever.