Is the Universe actually a giant quantum computer?
According to MIT professor Seth Lloyd, the answer is yes: "Everything in the universe is made of chunks of information called bits."
A researcher in Mechanical Engineering at MIT, Lloyd is one of the leaders in the field of quantum information. He’s been with the field from its very conception to its sky-rocketing rise to popularity. Decades ago, the feasibility of developing quantum computing devices was challenged. Now, as quantum computation is producing actual technologies, we are only left to wonder—what kind of applications will it provide us with next?
To begin understanding if the universe is a giant quantum computer—that is, a computer that operates using the principles of quantum mechanics—we must first understand the building blocks. What is information? According to Lloyd, everything in the universe is made of chunks of information called bits. These are the zeroes and ones that an engineer uses as the building blocks of computer software.
“But isn’t everything made of atoms?” you might ask. Lloyd has a clever answer to this, too. The atoms themselves are also bits of information. Information is everywhere, just like quantum mechanics. Tiny particles such as electrons, whose positions and velocities we cannot know for certain, are described by quantum mechanics. We can only give an estimate as to where an electron might be, and how fast it is moving. Before we make the measurement, the electron could be in any position.
What is the difference between regular and quantum computers? In a regular computer, information is encoded as bits interpreted as either 0 or 1. In a quantum computer, this information comes in slightly different variety – quantum bits, or “qubits”. It is physically allowed for this qubit to be in one state, in another, or somewhere in between. They can encode a combination of 1 and 0, thus being able to store or process much more information than regular bits. Unlike the bit that needs to be connected to the entire system to relay information, the qubit collapses instantly to relay information. How does this help us?
A small number of particles in the superposition of both 1 and 0 readings can give us an enormous amount of information—100 particles in superposition would mean representing every number from 1 to 2100 (a very, very large number). A classical computer can be designed to read one combination of three bits at a time, while a quantum computer will read all possible combinations. This means that quantum computers can process information in parallel. A system with any number N qubits will process 2N calculations at once, giving us a completely new and incredibly fast means of computing, such as factoring large numbers or evaluating extremely complex algorithms used for data analysis in finance, science, or cryptography.
What we care about the most is the time it takes the computer to apply an algorithm. For example, if you are given a map with hundreds of monuments in New York City, how long would it take you to find a tour that only visits each monument once? If someone gives you a tour, it is easy to check that the problem was solved correctly. This problem is called an NP-complete problem. Peter Shor of MIT showed in 1994 that a quantum computer can solve the NP-complete problem most efficiently; the time for computation only squares as the complexity increases. For classical computers, the time grows exponentially. Similarly, physical processes (such as the neural synapses in your brain or photosynthesis in plants) take the most efficient path, not just the fastest, giving us more parallels between reality and quantum computation.
Just like a quantum computer, physical processes involve the exchange and processing of information. Ed Fredkin first proposed that the universe could be a computer in the 1960’s, as well as Konrad Zuse who came up with the idea independently. In their view, the universe could be a type of computer called a cellular automaton, which describes a dynamic system that is broken apart into black and white grids, in which cells gather information from the surrounding cells on whether or not to change color. This is similar to the way a line or moving colony of ants might share information between each other about their surroundings, signaling to each other whether or not to follow a food trail.
However, this initial analogy to such sharing of information turned out to be not quite accurate. Regular computers are not so good at simulating quantum systems that do not follow the “yes” or “no” kind of signals, since quantum systems can have mixed signals! These are called the superposition of states, and can only be simulated by a quantum rather than classical computer. Since the universe itself is best described by quantum mechanics, Lloyd suggests that “quantum computing allows us to understand the universe in its own language.”
Physicists are not the only ones keen to reap the benefits of quantum computing; companies like IBM and Canadian D-wave as well as agencies like the CIA and NSA are also investing heavily in quantum computation research. The universe, however, might have already invested in a quantum computer. After all, information is processed in a very quantum mechanical way both on a tiny and large scale. The efficiency of these processes in our universe may very well suggest its true nature—of a quantum kind.
Originally written by Alexandra "Sasha" Churikova (edited for length)