All computing systems rely on a fundamental ability to store and manipulate information. Current computers manipulate individual bits, which store information as binary 0 and 1 states. Quantum computers leverage quantum mechanical phenomena to manipulate information. To do this, they rely on quantum bits, or qubits.
Quantum computers perform calculations based on the probability of an object’s state before it is measured – instead of just 1s or 0s – which means they have the potential to process exponentially more data compared to classical computers. A single state – such as on or off, up or down, 1 or 0 – is called a bit.
Quantum computing is an area of computing focused on developing computer technology based on the principles of quantum theory, which explains the behavior of energy and material on the atomic and subatomic levels.
‘The big difference compared to a classical computer is that a quantum computer is following a different rule set. It’s not using zeros and ones like classical computers are – bits and bytes – but it is actually able to work with something called qubits.
When researchers at Google announced last fall that they had achieved “ quantum superiority”—a point at which a quantum computer can perform a task beyond the reach of regular computers —some people wondered what the big deal was.
The first working 12-qubit quantum computer. D-Wave releases the first commercially available quantum computer. It costs $10m.
There are several models of quantum computers (or rather, quantum computing systems), including the quantum circuit model, quantum Turing machine, adiabatic quantum computer, one-way quantum computer, and various quantum cellular automata. The most widely used model is the quantum circuit.
IBM. In 2016, IBM was the first company to put a quantum computer on the cloud. The company has since built up an active community of more than 260,000 registered users, who run more than one billion every day on real hardware and simulators.
In 1998 Isaac Chuang of the Los Alamos National Laboratory, Neil Gershenfeld of the Massachusetts Institute of Technology (MIT), and Mark Kubinec of the University of California at Berkeley created the first quantum computer (2-qubit) that could be loaded with data and output a solution.
Right now, the best quantum computers have about 50 qubits. That’s enough to make them incredibly powerful, because every qubit you add means an exponential increase in processing capacity. But they also have really high error rates, because of those problems with interference. They’re powerful, but not reliable.
In a quantum computer, the basic unit of memory is a quantum bit or qubit. Qubits are made using physical systems, such as the spin of an electron or the orientation of a photon. These systems can be in many different arrangements all at once, a property known as quantum superposition.
Google announced it has a quantum computer that is 100 million times faster than any classical computer in its lab. Every day, we produce 2.5 exabytes of data. That number is equivalent to the content on 5 million laptops.
What can a quantum computer do that a classical computer can’t? Factoring large numbers, for starters. Multiplying two large numbers is easy for any computer. But calculating the factors of a very large (say, 500-digit) number, on the other hand, is considered impossible for any classical computer.
The Brain as a Classical Computer One is known in quantum physics as decoherence. Wave functions are fickle things. They like to spread out and get entangled to all kinds of other things from the outside of the quantum system.
A quantum computer by itself isn’t faster. Instead, it has a different model of computation. In this model, there are algorithms for certain (not all!) problems, which are asymptotically faster than the fastest possible (or fastest known, for some problems) classical algorithms.