Quantum Physics Revealed As Non-Mysterious This is one of several shortened indices into the Quantum Physics Sequence. Hello! You may have been directed to this page because you said something along the lines of "Quantum physics shows that reality doesn't exist apart from our observation of it," or "Science has disproved the idea of an objective reality," or even just "Quantum physics is one of the great mysteries of modern science; no one understands how it works." There was a time, roughly the first half-century after quantum physics was invented, when this was more or less true. The series of posts indexed below will show you - not just tell you - what's really going on down there. Some optional preliminaries you might want to read: Reductionism: We build models of the universe that have many different levels of description. And here's the main sequence: Quantum Explanations: Quantum mechanics doesn't deserve its fearsome reputation.
A tale of two qubits: how quantum computers work Quantum information is the physics of knowledge. To be more specific, the field of quantum information studies the implications that quantum mechanics has on the fundamental nature of information. By studying this relationship between quantum theory and information, it is possible to design a new type of computer—a quantum computer. A largescale, working quantum computer—the kind of quantum computer some scientists think we might see in 50 years—would be capable of performing some tasks impossibly quickly. To date, the two most promising uses for such a device are quantum search and quantum factoring. Although quantum search is impressive, quantum factoring algorithms pose a legitimate, considerable threat to security. Quantum computers are fundamentally different from classical computers because the physics of quantum information is also the physics of possibility. Single qubits. Pairs of qubits. Quantum physics 101. How do they work? Is the polarization horizontal or vertical?
Yves Couder In the first decades of the 20th century, physicists hotly debated how to make sense of the strange phenomena of quantum mechanics, such as the tendency of subatomic particles to behave like both particles and waves. One early theory, called pilot-wave theory, proposed that moving particles are borne along on some type of quantum wave, like driftwood on the tide. But this theory ultimately gave way to the so-called Copenhagen interpretation, which gets rid of the carrier wave, but with it the intuitive notion that a moving particle follows a definite path through space. Recently, Yves Couder, a physicist at Université Paris Diderot, has conducted a series of experiments in which millimeter-scale fluid droplets, bouncing up and down on a vibrated fluid bath, are guided by the waves that they themselves produce. The wave-particle duality is best illustrated by a canonical experiment in quantum mechanics that’s generally referred to as the two-slit, or two-hole, experiment. Scaling up
10 Enormous Numbers Technology One of the first questions that kids often ask is “What is the biggest number?” This question is an important step in transitioning to a world of abstract concepts. The answer is of course that numbers are generally considered endless, but there gets to be a point were numbers become so big that there really is no point in having them, they have no real importance outside of the fact that yes technically they do exist. Ten to the eightieth power – a 1 with 80 zeros after it – is quite massive but somewhat tangible at least from a relatively concrete point of view. The word googol, with a slightly different spelling, has become a frequently used verb in modern times, thanks to a highly popular search engine. A Plank length is extremely small, approximately 1.616199 x 10-35 meters, or in long form 0.00000000000000000000000000000616199 meters. The third largest number on this list, the number of all the plank volumes in the universe, consists of 185 digits. Sorry, had to do it.
Quantum entanglement Quantum entanglement is a physical phenomenon that occurs when pairs or groups of particles are generated or interact in ways such that the quantum state of each particle cannot be described independently – instead, a quantum state may be given for the system as a whole. Such phenomena were the subject of a 1935 paper by Albert Einstein, Boris Podolsky and Nathan Rosen,[1] describing what came to be known as the EPR paradox, and several papers by Erwin Schrödinger shortly thereafter.[2][3] Einstein and others considered such behavior to be impossible, as it violated the local realist view of causality (Einstein referred to it as "spooky action at a distance"),[4] and argued that the accepted formulation of quantum mechanics must therefore be incomplete. History[edit] However, they did not coin the word entanglement, nor did they generalize the special properties of the state they considered. Concept[edit] Meaning of entanglement[edit] Apparent paradox[edit] The hidden variables theory[edit]
Applications Quantum game theory Quantum game theory is an extension of classical game theory to the quantum domain. It differs from classical game theory in three primary ways: Superposed initial states,Quantum entanglement of initial states,Superposition of strategies to be used on the initial states. This theory is based on the physics of information much like quantum computing. Superposed initial states[edit] Entangled initial states[edit] The set of qubits which are initially provided to each of the players (to be used to convey their choice of strategy) may be entangled. Superposition of strategies to be used on initial states[edit] The job of a player in a game is to choose a strategy. Multiplayer games[edit] Introducing quantum information into multiplayer games allows a new type of equilibrium strategy which is not found in traditional games. See also[edit] References[edit] Notes Bibliography External links[edit]
Wave function collapse When the Copenhagen interpretation was first expressed, Niels Bohr postulated wave function collapse to cut the quantum world from the classical.[5] This tactical move allowed quantum theory to develop without distractions from interpretational worries. Mathematical description[edit] Mathematical background[edit] The quantum state of a physical system is described by a wave function (in turn – an element of a projective Hilbert space). This can be expressed in Dirac or bra–ket notation as a vector: The kets Where represents the Kronecker delta. An observable (i.e. measurable parameter of the system) is associated with each eigenbasis, with each quantum alternative having a specific value or eigenvalue, ei, of the observable. The coefficients c1, c2, c3... are the probability amplitudes corresponding to each basis . For simplicity in the following, all wave functions are assumed to be normalized; the total probability of measuring all possible states is unity: The process of collapse[edit] . .
How to Find and Care for a Pet Tardigrade ( Water Bear ) 'Water bears' is a colloquial name for tiny multicellular critters (typically 0.05-1.5mm long, depending on the species) that have always delighted microscopists. They are properly called tardigrades, and with four pairs of stumpy legs with a slow lumbering gait they do look like a microscopic bear (an eight legged, microscopic bear, that is). Tardigrades ( Water Bears ) live in moss and ferns. They are some of the most amazing animals on Earth. They can survive: Temperatures as low as -200 °C (-328 °F) and as high as 151 °C (304 °F);Freezing in a block of ice,Lack of oxygen,Lack of water for as long as decade(s).Levels of X-ray radiation 1000x the lethal human dose,Most noxious chemicals,Boiling alcohol,Low pressure of a vacuum; like that of space,And high pressure (up to 6x the pressure of the deepest part of the ocean). They may be microscopic, but are very cool! Ad Steps Give us 3 minutes of knowledge! Can you tell us about Painting doors? Removing paint? Mosquito control? Tips Warnings
Quantum geometry In theoretical physics, quantum geometry is the set of new mathematical concepts generalizing the concepts of geometry whose understanding is necessary to describe the physical phenomena at very short distance scales (comparable to Planck length). At these distances, quantum mechanics has a profound effect on physics. Quantum gravity[edit] In an alternative approach to quantum gravity called loop quantum gravity (LQG), the phrase "quantum geometry" usually refers to the formalism within LQG where the observables that capture the information about the geometry are now well defined operators on a Hilbert space. It is possible (but considered unlikely) that this strictly quantized understanding of geometry will be consistent with the quantum picture of geometry arising from string theory. Another, quite successful, approach, which tries to reconstruct the geometry of space-time from "first principles" is Discrete Lorentzian quantum gravity. Quantum states as differential forms[edit]
EPR paradox Albert Einstein The EPR paradox is an early and influential critique leveled against the Copenhagen interpretation of quantum mechanics. Albert Einstein and his colleagues Boris Podolsky and Nathan Rosen (known collectively as EPR) designed a thought experiment which revealed that the accepted formulation of quantum mechanics had a consequence which had not previously been noticed, but which looked unreasonable at the time. The scenario described involved the phenomenon that is now known as quantum entanglement. According to quantum mechanics, under some conditions, a pair of quantum systems may be described by a single wave function, which encodes the probabilities of the outcomes of experiments that may be performed on the two systems, whether jointly or individually. At the time the EPR article discussed below was written, it was known from experiments that the outcome of an experiment sometimes cannot be uniquely predicted. History of EPR developments[edit] Einstein's opposition[edit]