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Almost a century ago, renowned quantum theorist Werner Heisenberg found fundamental limits on how well a quantum system can be prepared and measured, known as Heisenberg's uncertainty principle. However, only the limit that pertains to the preparation of quantum systems has been quantified; the other two, relating to measurements, have long been a matter of debate, lacking a formal treatment. These limits are: That it is impossible to jointly measure incompatible quantities, for instance, location and speed of a quantum object, with perfect accuracy; and that a measurement of one of these quantities necessarily disturbs the other. Last year, UQ's...

In a paper published in the current issue of the scientific journal Nature Communications and titled "Direct measurement of a 27-dimensional orbital-angular-momentum state vector," a team of physicists led by the University of Rochester's Mehul Malik describe how they circumvented a basic principle of uncertainty that requires that some states of a quantum system must be understood poorly if other states are to be understood well. Determining a quantum state, such as the position of an electron or the momentum of a photon, is tricky, to say the least. That's because subatomic particles behave nothing at all like billiard balls,...

Physicists have spent a century puzzling over the paradoxes of quantum theory. Now a few of them are trying to reinvent it. If the truth be told, few physicists have ever really felt comfortable with quantum theory. Having lived with it now for more than a century, they have managed to forge a good working relationship; physicists now routinely use the mathematics of quantum behaviour to make stunningly accurate calculations about molecular structure, high-energy particle collisions, semiconductor behaviour, spectral emissions and much more. But the interactions tend to be strictly formal. As soon as researchers try to get behind the...

According to the First Law of Thermodynamics, nothing in the Universe (i.e., matter or energy) can pop into existence from nothing (see Miller, 2013). All of the scientific evidence points to that conclusion. So, the Universe could not have popped into existence before the alleged “big bang” (an event which we do not endorse). Therefore, God must have created the Universe. One of the popular rebuttals by the atheistic community is that quantum mechanics could have created the Universe. In 1905, Albert Einstein proposed the idea of mass-energy equivalence, resulting in the famous equation, E = mc2 (1905). We now...

The effects of relativity can be seen in everyday phenomena © ShutterstockWhy is mercury a liquid at room temperature? If you ask that question in a school classroom you will probably be told that relativity affects the orbitals of heavy metals, contracting them and changing how they bond. However, the first evidence that this explanation is correct has only just been published.An international team led by Peter Schwerdtfeger of Massey University Auckland in New Zealand used quantum mechanics to make calculations of the heat capacity of the metal either including or excluding relativistic effects. They showed that if they...

Government Lab Reveals It Has Operated Quantum Internet for Over Two Years A quantum internet capable of sending perfectly secure messages has been running at Los Alamos National Labs for the last two and a half years, say researchers One of the dreams for security experts is the creation of a quantum internet that allows perfectly secure communication based on the powerful laws of quantum mechanics.The basic idea here is that the act of measuring a quantum object, such as a photon, always changes it. So any attempt to eavesdrop on a quantum message cannot fail to leave telltale signs...

Two new studies to be published in the European Physical Journal D demonstrate that the speed of light is variable in real space. Textbook explanations of the speed of light assume that light travels in a vacuum, but space is not a vacuum. … It is not expected that the small variation in the speed of light which has been found will affect the universally accepted theories of particle physics and quantum mechanics to a large extent. However, the studies are proof that the speed of light may be variable, and shows that the mathematical treatments that have long been...

Particles do not retain "information", don't have "knowledge". It is not that the act of observation that alters reality. In fact the physical nature of the "observation" small though it may be is sufficient to alter the metrics of sub atomic particles.

When quantum mechanics meets general relativityThe unification of quantum mechanics and Einstein's general relativity is one of the most exciting and still open questions in modern physics. General relativity, the joint theory of gravity, space and time gives predictions that become clearly evident on a cosmic scale of stars and galaxies. Quantum effects, on the other hand, are fragile and are typically observed on small scales, e.g. when considering single particles and atoms. That is why it is very hard to test the interplay between quantum mechanics and general relativity. Now theoretical physicists led by Prof. ÄŒaslav Brukner at the...

Researchers have bent one of the most basic rules of quantum mechanics, a counterintuitive branch of physics that deals with atomic-scale interactions. Its "complementarity" rule asserts that it is impossible to observe light behaving as both a wave and a particle, though it is strictly both. In an experiment reported in Science, researchers have now done exactly that. They say the feat "pulls back the veil" on quantum reality in a way that was thought to be prohibited by theory. Quantum mechanics has spawned and continues to fuel spirited debates about the nature of what we can see and measure,...

Researchers claim to have produced sought-after quantum effect. A team of physicists is claiming to have coaxed sparks from the vacuum of empty space1. If verified, the finding would be one of the most unusual experimental proofs of quantum mechanics in recent years and "a significant milestone", says John Pendry, a theoretical physicist at Imperial College London who was not involved in the study. The researchers, based at the Chalmers University of Technology in Gothenburg, Sweden, will present their findings early next week at a workshop in Padua, Italy. They have already posted a paper on the popular pre-print server...

Quantum physicists at the Massachusetts Institute of Technology believe it is possible to create a time machine which could affect the past without creating a "grandfather paradox".Scientists have for some years been able to 'teleport' quantum states from one place to another. Now Seth Lloyd and his MIT team say that, using the same principles and a further strange quantum effect known as 'postselection', it should be possible to do the same backwards in time. Lloyd told the Technology Review: "It is possible for particles (and, in principle, people) to tunnel from the future to the past."

A fresh take on a classic experiment makes no progress in unifying quantum mechanics and relativity. If you ever want to get your head around the riddle that is quantum mechanics, look no further than the double-slit experiment. This shows, with perfect simplicity, how just watching a wave or a particle can change its behaviour. The idea is so unpalatable to physicists that they have spent decades trying to find new ways to test it. The latest such attempt, by physicists in Europe and Canada, used a three-slit version — but quantum mechanics won out again. In the standard double-slit...

A radical reformulation of quantum mechanics suggests that the universe has a set destiny and its pre-existing fate reaches back in time to influence the past. It could explain the origin of life, dark energy and solve other cosmic conundrums.The universe has a destiny—and this set fate could be reaching backwards in time and combining with influences from the past to shape the present. It’s a mind-bending claim, but some cosmologists now believe that a radical reformulation of quantum mechanics in which the future can affect the past could solve some of the universe’s biggest mysteries, including how life arose....

Acin and a colleague cobbled together ytterbium atoms to produce “true” randomness, by which they mean the results of an electron being “up” or “down” cannot be predicted skillfully using any information. In their experiment, the information on the ytterbium atoms’ quantum (which means discrete!) state is not humanly accessible, so we can never do better than always guessing “up”. Brain teaser for advanced readers. Acin’s experiment generates an “up” or “down”, each occurring half the time unpredictably. Why is guessing “up” every time better than switching guesses between “up” and “dow

Enlarge Image Springboard. This little vibrating widget has been eased into the simplest quantum state of motion. Credit: O'Connell et al., Nature, Advance Online Publication (2010) The weird rules of quantum mechanics state that a tiny object can absorb energy only in discrete amounts, or quanta, and can literally be in two places simultaneously. Those mind-bending tenets have been amply demonstrated in experiments with electrons, photons, atoms, and molecules. Ironically, though, physicists have never observed such bizarre quantum-mechanical effects in the motion of a human-made mechanical device. Now, Andrew Cleland, John Martinis, and colleagues at the University of California,...

Largest ever object put into quantum state.A team of scientists has succeeded in putting an object large enough to be visible to the naked eye into a mixed quantum state of moving and not moving. Andrew Cleland at the University of California, Santa Barbara, and his team cooled a tiny metal paddle until it reached its quantum mechanical 'ground state' — the lowest-energy state permitted by quantum mechanics. They then used the weird rules of quantum mechanics to simultaneously set the paddle moving while leaving it standing still. The experiment shows that the principles of quantum mechanics can apply...

Table-top experiments unlock quantum realm predicted by Dirac equation. Trapped ions masquerading as high-speed particles have been used to confirm a bizarre 80-year-old prediction of quantum mechanics. Quantum particles racing at close to the speed of light were first predicted to jitter violently as they moved — a phenomenon known as the Zitterbewegung — in 1930, by the father of quantum mechanics, Erwin Schrödinger. The prediction was based on the Dirac equation, developed by British physicist Paul Dirac in 1928, which merges quantum mechanics with special relativity to describe how particles such as electrons behave. "The motion is particularly unexpected...

The typical Hollywood action hero skirts death for a living. Time and again, scores of bad guys shoot at him from multiple directions but miss by a hair. Cars explode just a fraction of a second too late for the fireball to catch him before he finds cover. And friends come to the rescue just before a villain’s knife slits his throat. If any one of those things happened just a little differently, the hero would be hasta la vista, baby. Yet even if we have not seen the movie before, something tells us that he will make it to...

To a physicist, life seems little short of miraculous — all those stupid atoms getting together to perform such clever tricks! For centuries, living organisms were regarded as some sort of magic matter. Today, we know that no special “life force” is at work in biology; there is just ordinary matter doing extraordinary things, all the while obeying the familiar laws of physics. What, then, is the secret of life’s remarkable properties? In the late 1940s and 1950s it was fashionable to suppose that quantum mechanics — or perhaps some soon-to-be-formulated “post-quantum mechanics” — held the key to the mystery...