Un nuevo experimento en Par\u00eds ha demostrado, por primera vez, que la comunicaci\u00f3n cu\u00e1ntica es superior a las formas cl\u00e1sicas de transmisi\u00f3n de informaci\u00f3n.<\/p>\n
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Quantum computers\u00a0are still a dream, but the era of\u00a0quantum communication\u00a0is here. A\u00a0new experiment\u00a0out of Paris has demonstrated, for the first time, that quantum communication is superior to classical ways of transmitting information.<\/p>\n
\u201cWe are the first to show a quantum advantage for transmitted information that two parties have to share to perform a useful task,\u201d said\u00a0Eleni Diamanti, an electrical engineer at Sorbonne University and a co-author of the result along with\u00a0Iordanis Kerenidis, a computer scientist at Paris Diderot University, and\u00a0Niraj Kumar.<\/p>\n
Quantum machines \u2014 which exploit quantum properties of matter to encode information \u2014 are widely expected to\u00a0revolutionize computing. But progress has been\u00a0slow. While engineers labor to build\u00a0rudimentary quantum computers, theoretical computer scientists have confronted a more fundamental obstacle: They\u2019ve been unable to prove that classical computers will never be able to perform the tasks quantum computers are designed for. This past summer, for example, a teenager from Texas proved that a problem long thought to be quickly solvable only on a quantum computer\u00a0can be donerapidly on a classical computer as well.<\/p>\n
However, in the realm of communication (rather than computation), the benefits of a quantum approach are certifiable. More than a decade ago computer scientists proved that, at least theoretically, quantum communication beats classical ways of sending messages for certain tasks.<\/p>\n
\u201cMostly people have looked at computational tasks. One big advantage is that with communication tasks, the advantages are provable,\u201d Kerenidis said.<\/p>\n
In 2004, Kerenidis and two other computer scientists imagined\u00a0a scenario\u00a0in which one person needed to send information to another so that the second person could answer a particular question. The researchers proved that a quantum setup could accomplish the task by transmitting exponentially less information than a classical system. But the quantum setup they imagined was purely theoretical\u2014and far beyond the technology of the time.<\/p>\n
\u201cWe could prove this quantum advantage, but it was difficult to actually implement the quantum protocol,\u201d Kerenidis said.<\/p>\n
The new work carries out a modified version of the scenario that Kerenidis and colleagues envisaged. The question addressed in the paper involves two users, Alice and Bob. Alice has a set of numbered balls. Each ball is randomly colored red or blue. Bob wants to know whether a particular pair of balls, chosen at random, has the same color or different colors. Alice wants to send Bob the smallest amount of information she can while still ensuring that Bob can answer his question.<\/p>\n
This problem is called the \u201csampling matching problem.\u201d It has implications for cryptography and digital currency, where users often want to exchange information without necessarily divulging everything they know. It\u2019s also well-suited to demonstrating a quantum communication advantage.<\/p>\n
\u201cYou can\u2019t just say, \u2018I want to send you a movie or something that\u2019s one gigabyte and encode it into a quantum state\u2019\u201d and expect to find a quantum advantage, said\u00a0Thomas Vidick, a computer scientist at the California Institute of Technology. \u201cYou have to look at tasks that are more subtle.\u201d<\/p>\n
To solve the matching problem classically, Alice has to send Bob an amount of information proportional to the square root of the number of balls. But the unorthodox nature of quantum information makes a more efficient solution possible.<\/p>\n In the laboratory setup used in the new work, Alice and Bob communicate via laser pulses. Each pulse represents a single ball. The pulses go through a beam splitter, which sends half of each pulse toward Alice and half toward Bob. As a pulse passes by Alice, she can shift something called the phase of the laser pulse to encode information about each ball \u2014 whether it\u2019s red or blue.<\/p>\n\n![\"\"](\"https:\/\/media.wired.com\/photos\/5c1ce092d583c6192e66cc7d\/master\/w_1120,c_limit\/QuantumSpeedup_560-3.jpg\")
<\/div>\n<\/div><\/i>LUCY READING-IKKANDA\/QUANTA MAGAZINE<\/cite><\/div>\n<\/figcaption><\/figure>\n