quantum computer based on superconducting qubits
developed by ibm research
. the qubits in the device shown here will be cooled to under 1 kelvin
using a dilution refrigerator
quantum computing is the use of quantum-mechanical phenomena such as superposition and entanglement to perform computation. a quantum computer, implemented theoretically or physically, is used to perform such computation.:i-5 there are currently two main approaches to physically implementing a quantum computer: analog and digital. analog approaches are further divided into quantum simulation, quantum annealing, and adiabatic quantum computation. digital quantum computers use quantum logic gates to do computation. both approaches use quantum bits or qubits.:2–13
quantum computing began in the early 1980s, when physicist paul benioff proposed a quantum mechanical model of the turing machine. richard feynman and yuri manin later suggested that a quantum computer had the potential to simulate things that a classical computer could not. in 1994, peter shor developed a quantum algorithm for factoring integers that had the potential to decrypt rsa-encrypted communications. despite ongoing experimental progress since the late 1990s, most researchers believe that "fault-tolerant quantum computing [is] still a rather distant dream". on 23 october 2019, google ai, in partnership with the u.s. national aeronautics and space administration (nasa), published a paper in which they claimed to have achieved quantum supremacy. while some have disputed this claim, it is still a significant milestone in the history of quantum computing.
quantum computing is modeled by quantum circuits. quantum circuits are based on the quantum bit, or "qubit", which is somewhat analogous to the bit in classical computation. qubits can be in a 1 or 0 quantum state, or they can be in a superposition of the 1 and 0 states. however, when qubits are measured the result is always either a 0 or a 1; the probabilities of these two outcomes depend on the quantum state that they were in immediately prior to the measurement. computation is performed by manipulating qubits with quantum logic gates, which are somewhat analogous to classical logic gates.
the field of quantum computing is a subfield of quantum information science, which includes quantum cryptography and quantum communication.