Quantum computing

Quantum computing is the use of quantum-mechanical phenomena such as superposition and entanglement to perform computation. A quantum computer is used to perform such computation, which can be implemented theoretically or physically. There are two main approaches to physically implementing a quantum computer: analog and digital. Analog approaches are further divided into quantum simulation, quantum annealing, adiabatic quantum computation. Digital quantum computers use quantum logic gates to do computation. Both approaches use quantum qubits. Qubits are fundamental to quantum computing and are somewhat analogous to bits in a classical computer. 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. 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 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 all secured communications. Despite ongoing experimental progress since the late 1990s, most researchers believe that "fault-tolerant quantum computing still a rather distant dream". On 23 October 2019, Google AI, in partnership with the U. S. National Aeronautics and Space Administration, 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; the field of quantum computing is a subfield of quantum information science, which includes quantum cryptography and quantum communication. The prevailing model of quantum computation describes the computation in terms of a network of quantum logic gates. A memory consisting of n bits of information has 2 n possible states. A vector representing all memory states has hence 2 n entries; this vector should be viewed as a probability vector and represents the fact that the memory is to be found in a particular state.

In the classical view, one entry would have a value of 1 and all other entries would be zero. In quantum mechanics, probability vectors are generalized to density operators; this is the technically rigorous mathematical foundation for quantum logic gates, but the intermediate quantum state vector formalism is introduced first because it is conceptually simpler. This article focuses on the quantum state vector formalism for simplicity. We begin by considering a simple memory consisting of only one bit; this memory may be found in one of two states: the one state. We may represent the state of this memory using Dirac notation so that A quantum memory may be found in any quantum superposition | ψ ⟩ of the two classical states | 0 ⟩ and | 1 ⟩: In general, the coefficients α and β are complex numbers. In this scenario, one qubit of information is said to be encoded into the quantum memory; the state | ψ ⟩ is not itself a probability vector but can be connected with a probability vector via a measurement operation.

If the quantum memory is measured to determine if the state is | 0 ⟩ or | 1 ⟩, the zero state would be observed with probability | α | 2 and the one state with probability | β | 2. The numbers α and β are called quantum amplitudes; the state of this one-qubit quantum memory can be manipulated by applying quantum logic gates, analogous to how classical memory can be manipulated with classical logic gates. One important gate for both classical and quantum computation is the NOT gate, which can be represented by a matrix Mathematically, the application of such a logic gate to a quantum state vector is modelled with matrix multiplication, thus X | 0 ⟩ = | 1 ⟩ and X | 1 ⟩ = | 0 ⟩. The mathematics of single qubit gates can be extended to operate on multiqubit quantum memories in two important ways. One way is to select a qubit and apply that gate to the target qubit whilst leaving the remainder of the memory unaffected. Another way is to apply the gate to its target only if another part of the memory is in a desired state.

These two choices can be illustrated using another example. The possible states of a two-qubit quantum memory are The CNOT gate can be represented using the following matrix: As a mathematical consequence of this definition, C N O T | 00 ⟩ = | 00 ⟩, C N O T

Estremenho dialect

Estremenho is a dialect of the European Portuguese spoken in the former provinces of Estremadura and Beira Litoral and is part of the central-southern dialects. The variety of Lisbon, used to form the basis for the pattern of European Portuguese, is within this dialect; the Estremenhan dialects present the following characteristics: A generalized monophthongization of the diphthong. For example, "touro" and "roupa" passes to "tôro" and "rôpa". In certain subregions, such as saloia, a monophthongization of the diphthong occurs. For example, "manêra" instead of "maneira", although this has evolved into in the Lisbon dialect; the predorsodental sibilants, that is, /s/ and /z/, are pronounced as in the European pattern and are well distinguished from the lower x and the j, contrary to what happens with the northern dialects. Sound recordings of the dialect New proposal for the classification of Galician-Portuguese dialects by Luís Lindley Cintra Portuguese dialects

Electronic mailing list

An electronic mailing list or email list is a special use of email that allows for widespread distribution of information to many Internet users. It is similar to a traditional mailing list – a list of names and addresses – as might be kept by an organization for sending publications to its members or customers, but refers to four things: a list of email addresses, the people receiving mail at those addresses, thus defining a community gathered around a topic of interest; the publications sent to those addresses, a reflector, a single email address that, when designated as the recipient of a message, will send a copy of that message to all of the subscribers. Electronic mailing lists are or automated through the use of special mailing list software and a reflector address set up on a server capable of receiving email. Incoming messages sent to the reflector address are processed by the software, depending on their content, are acted upon internally or are distributed to all email addresses subscribed to the mailing list.

A web-based interface is available to allow people to subscribe and change their preferences. However, mailing list servers existed long before the World Wide Web, so most accept commands over email to a special email address; this allows subscribers to perform such tasks as subscribing and unsubscribing, temporarily halting the sending of messages to them, or changing available preferences - all via email. The common format for sending these commands is to send an email that contains the command followed by the name of the electronic mailing list the command pertains to. Examples: subscribe anylist or subscribe anylist John Doe. Electronic mailing list servers may be set to forward messages to subscribers of a particular mailing list either individually as they are received by the list server, or in digest form in which all messages received on a particular day by the list server are combined into one email, sent once per day to subscribers; some mailing lists allow individual subscribers to decide how they prefer to receive messages from the list server.

Mailing lists have first been scholarly mailing lists. The genealogy of mailing lists as a communication tool between scientists can be traced back to the times of the fledgling Arpanet; the aim of the computer scientists involved in this project was to develop protocols for the communication between computers. In so doing, they have built the first tools of human computer-mediated communication. Broadly speaking, the scholarly mailing lists can be seen as the modern version of the salons of the Enlightenment ages, designed by scholars for scholars; the “threaded conversation” structure is a typical and ubiquitous structure of discourse within lists and fora of the Internet. It is pivotal to the structure and topicality of debates within mailing lists as an arena, or public sphere in Habermas wording; the flame wars give valuable and unique information to historians to comprehend what is at stake in the communities gathered around lists. Anthropologists and historians have used mailing lists as fieldwork.

Topics include TV series fandom, online culture, or scientific practices among many other academic studies. From the historian's point of view, the issue of the preservation of mailing lists heritage is essential. Not only the text of the corpus of messages has yet to be perennially archived, but their related metadata, headers that define topics, etc. Mailing lists archives are a unique opportunity for historians to explore interactions, debates tensions that reveal a lot about communities. One type of electronic mailing list is an announcement list, used as a one-way conduit of information and may only be "posted to" by selected people; this may be referred to by the term newsletter. Newsletter and promotional emailing lists are employed in various sectors as parts of direct marketing campaigns. Another type of electronic mailing list is a discussion list. On a discussion list, a subscriber uses the mailing list to send messages to all the other subscribers, who may answer in similar fashion.

Thus, actual discussion and information exchanges can happen. Mailing lists of this type are topic-oriented, the topic may range from narrow to "whatever you think could interest us". In this they are similar to Usenet newsgroups, another form of discussion group that may have an aversion to off-topic messages. On both discussion lists and newsletter lists precautions are taken to avoid spamming. Discussion lists require every message to be approved by a moderator before being sent to the rest of the subscribers, although higher-traffic lists only moderate messages from new subscribers. Companies sending out promotional newsletters have the option of working with whitelist mail distributors, which agree to standards and high fines from ISPs should any of the opt-in subscribers complain. In exchange for their compliance and agreement to prohibitive fines, the emails sent by whitelisted companies are not blocked by spam filters, which can reroute these legitimate, non-spam emails; some mailing lists are open to anyone who wants to join them, while others require an approval from the list owner before one may join.

Joining a mailing list is called "subscribing" and