Quantum computing\u00c2\u00a0is the use of\u00c2\u00a0quantum-mechanical\u00c2\u00a0phenomena such as\u00c2\u00a0superposition\u00c2\u00a0and\u00c2\u00a0entanglement\u00c2\u00a0to perform\u00c2\u00a0computation. Computers that perform quantum computations are known as\u00c2\u00a0quantum computers.\u00c2\u00a0Quantum computers are believed to be able to solve certain\u00c2\u00a0computational problems, such as\u00c2\u00a0integer factorization\u00c2\u00a0(which underlies\u00c2\u00a0RSA encryption), substantially faster than classical computers. The study of quantum computing is a subfield of\u00c2\u00a0quantum information science.<\/p>\n
Quantum computing began in the early 1980s, when physicist\u00c2\u00a0Paul Benioff\u00c2\u00a0proposed a quantum mechanical model of the\u00c2\u00a0Turing machine.\u00c2\u00a0Richard Feynman\u00c2\u00a0and\u00c2\u00a0Yuri Manin\u00c2\u00a0later suggested that a quantum computer had the potential to simulate things that a\u00c2\u00a0classical computer\u00c2\u00a0could not.\u00c2\u00a0In 1994,\u00c2\u00a0Peter Shor\u00c2\u00a0developed a quantum\u00c2\u00a0algorithm\u00c2\u00a0for\u00c2\u00a0factoring integers\u00c2\u00a0that had the potential to decrypt\u00c2\u00a0RSA-encrypted communications.\u00c2\u00a0Despite ongoing experimental progress since the late 1990s, most researchers believe that “fault-tolerant\u00c2\u00a0quantum computing [is] still a rather distant dream.”\u00c2\u00a0In recent years, investment into quantum computing research has increased in both the public and private sector.\u00c2\u00a0On 23 October 2019,\u00c2\u00a0Google AI, in partnership with the U.S. National Aeronautics and Space Administration (NASA), published a paper in which they claimed to have achieved\u00c2\u00a0quantum supremacy.\u00c2\u00a0While some have disputed this claim, it is still a significant milestone in the history of quantum computing.<\/p>\n
There are several models of quantum computing, including the\u00c2\u00a0quantum circuit model,\u00c2\u00a0quantum Turing machine,\u00c2\u00a0adiabatic quantum computer,\u00c2\u00a0one-way quantum computer, and various\u00c2\u00a0quantum cellular automata. The most widely used model is the\u00c2\u00a0quantum circuit. Quantum circuits are based on the quantum bit, or “qubit”, which is somewhat analogous to the\u00c2\u00a0bit\u00c2\u00a0in classical computation. Qubits can be in a 1 or 0\u00c2\u00a0quantum state, or they can be in a\u00c2\u00a0superposition\u00c2\u00a0of the 1 and 0 states. However, when qubits are measured the result is always either a 0 or a 1; the\u00c2\u00a0probabilities\u00c2\u00a0of these two outcomes depend on the\u00c2\u00a0quantum state\u00c2\u00a0that the qubits were in immediately prior to the measurement. Computation is performed by manipulating qubits with\u00c2\u00a0quantum logic gates, which are somewhat analogous to\u00c2\u00a0classical logic gates.<\/p>\n
There are currently two main approaches to physically implementing a quantum computer: analog and digital. Analog approaches are further divided into\u00c2\u00a0quantum simulation,\u00c2\u00a0quantum annealing, and\u00c2\u00a0adiabatic quantum computation. Digital quantum computers use\u00c2\u00a0quantum logic gates\u00c2\u00a0to do computation. Both approaches use quantum bits or\u00c2\u00a0qubits.[1]<\/sup>:2\u00e2\u20ac\u201c13<\/sup>\u00c2\u00a0There are currently a number of significant obstacles in the way of constructing useful quantum computers. In particular, it is difficult to maintain the quantum states of qubits as they are prone to\u00c2\u00a0quantum decoherence, and quantum computers require significant\u00c2\u00a0error correction\u00c2\u00a0as they are far more prone to errors than classical computers.<\/p>\n Any\u00c2\u00a0computational problem\u00c2\u00a0that can be solved by a classical computer can also, in principle, be solved by a quantum computer. Conversely, quantum computers obey the\u00c2\u00a0Church\u00e2\u20ac\u201cTuring thesis; that is, any\u00c2\u00a0computational problem\u00c2\u00a0that can be solved by a quantum computer can also be solved by a classical computer. While this means that quantum computers provide no additional power over classical computers in terms of\u00c2\u00a0computability, they do in theory provide additional power when it comes to the\u00c2\u00a0time complexity\u00c2\u00a0of solving certain problems. Notably, quantum computers are believed to be able to quickly solve certain problems that no classical computer could solve in\u00c2\u00a0any feasible amount of time\u00e2\u20ac\u201da feat known as “quantum supremacy.” The study of the\u00c2\u00a0computational complexity\u00c2\u00a0of problems with respect to quantum computers is known as\u00c2\u00a0quantum complexity theory.<\/p>\n Besides factorization and discrete logarithms, quantum algorithms offering a more than polynomial speedup over the best known classical algorithm have been found for several problems,\u00c2\u00a0including the simulation of quantum physical processes from chemistry and solid state physics, the approximation of\u00c2\u00a0Jones polynomials, and solving\u00c2\u00a0Pell’s equation. No mathematical proof has been found that shows that an equally fast classical algorithm cannot be discovered, although this is considered unlikely.\u00c2\u00a0However, quantum computers offer polynomial speedup for some problems. The most well-known example of this is\u00c2\u00a0quantum database search<\/i>, which can be solved by\u00c2\u00a0Grover’s algorithm\u00c2\u00a0using quadratically fewer queries to the database than that are required by classical algorithms. In this case, the advantage is not only provable but also optimal, it has been shown that Grover’s algorithm gives the maximal possible probability of finding the desired element for any number of oracle lookups. Several other examples of provable quantum speedups for query problems have subsequently been discovered, such as for finding collisions in two-to-one functions and evaluating NAND trees.<\/p>\n Problems that can be addressed with\u00c2\u00a0Grover’s algorithm\u00c2\u00a0have the following properties:<\/p>\n For problems with all these properties, the running time of\u00c2\u00a0Grover’s algorithm\u00c2\u00a0on a quantum computer will scale as the square root of the number of inputs (or elements in the database), as opposed to the linear scaling of classical algorithms. A general class of problems to which\u00c2\u00a0Grover’s algorithm\u00c2\u00a0can be applied\u00c2\u00a0is\u00c2\u00a0Boolean satisfiability problem. In this instance, the\u00c2\u00a0database<\/i>\u00c2\u00a0through which the algorithm is iterating is that of all possible answers. An example (and possible) application of this is a\u00c2\u00a0password cracker\u00c2\u00a0that attempts to guess the password or secret key for an\u00c2\u00a0encrypted\u00c2\u00a0file or system.\u00c2\u00a0Symmetric ciphers\u00c2\u00a0such as\u00c2\u00a0Triple DES\u00c2\u00a0and\u00c2\u00a0AES\u00c2\u00a0are particularly vulnerable to this kind of attack.\u00c2\u00a0This application of quantum computing is a major interest of government agencies.<\/p>\n Since chemistry and nanotechnology rely on understanding quantum systems, and such systems are impossible to simulate in an efficient manner classically, many believe\u00c2\u00a0quantum simulation\u00c2\u00a0will be one of the most important applications of quantum computing.\u00c2\u00a0Quantum simulation could also be used to simulate the behavior of atoms and particles at unusual conditions such as the reactions inside a\u00c2\u00a0collider.<\/p>\n Quantum annealing\u00c2\u00a0or\u00c2\u00a0Adiabatic quantum computation\u00c2\u00a0relies on the adiabatic theorem to undertake calculations. A system is placed in the ground state for a simple Hamiltonian, which is slowly evolved to a more complicated Hamiltonian whose ground state represents the solution to the problem in question. The adiabatic theorem states that if the evolution is slow enough the system will stay in its ground state at all times through the process.<\/p>\n The\u00c2\u00a0Quantum algorithm for linear systems of equations, or “HHL Algorithm”, named after its discoverers Harrow, Hassidim, and Lloyd, is expected to provide speedup over classical counterparts.<\/p>\n The above is a brief about Quantum Computing. Watch this space for more updates on the latest trends in Technology.<\/p>\n","protected":false},"excerpt":{"rendered":" Quantum computing\u00c2\u00a0is the use of\u00c2\u00a0quantum-mechanical\u00c2\u00a0phenomena<\/p>\n","protected":false},"author":1,"featured_media":1759,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[940,360,7],"tags":[941,361,18],"class_list":["post-1757","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-computation","category-quantum-computing","category-techtrends","tag-computation","tag-quantum-computing","tag-technology"],"_links":{"self":[{"href":"https:\/\/blog.amt.in\/index.php\/wp-json\/wp\/v2\/posts\/1757","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blog.amt.in\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.amt.in\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.amt.in\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.amt.in\/index.php\/wp-json\/wp\/v2\/comments?post=1757"}],"version-history":[{"count":1,"href":"https:\/\/blog.amt.in\/index.php\/wp-json\/wp\/v2\/posts\/1757\/revisions"}],"predecessor-version":[{"id":1758,"href":"https:\/\/blog.amt.in\/index.php\/wp-json\/wp\/v2\/posts\/1757\/revisions\/1758"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blog.amt.in\/index.php\/wp-json\/wp\/v2\/media\/1759"}],"wp:attachment":[{"href":"https:\/\/blog.amt.in\/index.php\/wp-json\/wp\/v2\/media?parent=1757"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.amt.in\/index.php\/wp-json\/wp\/v2\/categories?post=1757"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.amt.in\/index.php\/wp-json\/wp\/v2\/tags?post=1757"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}\n