Long-range tunneling of quantum particles

Long-range tunneling of quantum particles: Experimental physicists in Innsbruck, Austria, have now directly observed quantum particles transmitting through a whole series of up to five potential barriers under conditions where a single particle could not do the move.

Quantum mechanics enables 'impossible' space chemistry - physics-math - 30 June 2013 - New Scientist

 Quantum mechanics enables 'impossible' space chemistry - physics-math - 30 June 2013 - New Scientist:  Another route to methoxy is to combine a hydroxyl radical and methanol gas, both present in space. But this reaction requires hurdling a significant energy barrier – and the energy to do that simply isn't available in the cold expanse of space.

Heard and his colleagues wondered if the answer lay in quantum mechanics: a process called quantum tunnelling might give the hydroxyl radical a small chance to cheat by digging through the barrier instead of going over it, they reasoned.

So, in another attempt to replicate the production of methoxy in space, the team chilled gaseous hydroxyl and methanol to 63 kelvin – and were able to produce methoxy...

The team also found that the reaction occurred 50 times faster via quantum tunnelling than if it occurred normally at room temperature by hurdling the energy barrier.

Google's Quantum Computer Proven To Be Real Thing (Almost) | Wired Enterprise | Wired.com

Google's Quantum Computer Proven To Be Real Thing (Almost) | Wired Enterprise | Wired.com


What they can say for sure is that the system doesn’t use simulated annealing, which is essentially a means of searching for a mathematical solution. According to Lidar, simulated annealing is akin to looking for the lowest possible point in a vast landscape.

“We call it an energy landscape,” he says. “There is a solution hiding somewhere in that landscape, and you can imagine that solution is hiding at the lowest point on the surface. You’re trying to find that lowest point.” This is done by randomly traveling across the landscape, moving down “hills” and back up them, until you locate the deepest valley.

This strategy relies purely on classical physics, not quantum physics. But Lidar says the D-wave is “consistent” with quantum annealing. This is similar to simulated annealing — except you can, in essence, go through the hills rather than over them. “You can take advantage of a quantum phenomenon called tunneling,” Lidar says. “It’s like a quantum shortcut.” He’s careful to say that he and his team have not proven that the D-Wave uses quantum annealing, but the system certainly appears to use it.

Gravity-less toy black hole solves cosmic puzzles

Gravity-less toy black hole solves cosmic puzzles: His team modelled a minimal black hole, defined only by having an inside and an outside, using quantum theory. To their surprise, they found that this object reproduces a lot of the features of real black holes that are thought to rely on gravity, including Hawking radiation, which could occur via a process called quantum tunneling.

This chimes with suggestions that gravity is not a fundamental component of the universe but an emergent property of quantum mechanics, just as waves are an emergent property of water molecules.

Controversial quantum computer aces entanglement tests

Controversial quantum computer aces entanglement tests: D-Wave instead uses adiabatic quantum computing, in which an array of chilled, superconducting niobium loops – the qubits in this system – very quickly find the lowest point in what can be thought of as an energy "landscape" of hills and valleys...


Spedalieri and colleagues applied a mathematical test that determines whether there are any ways for non-entangled qubits to arrange themselves to be compatible with the data. If not, the system must be entangled.

Using this test, they found evidence for entanglement. What's more, it was at a similar stage in the computation to where D-Wave also found evidence for entanglement, based on energy distribution.

'Tunneling of the third kind' experiment could search for new physics

'Tunneling of the third kind' experiment could search for new physics: In tunneling of the third kind, a quantum particle that cannot pass through a barrier changes into a pair of virtual particles that pass through the barrier before changing back into the first particle. Gies, along with coauthor Joerg Jaeckel, discovered this kind of tunneling in 2009. They suggested that this tunneling could take the form of photons changing into MCPs, which can tunnel through certain barriers and then change back into photons. Like the second kind of tunneling, this kind would also appear as light shining through a wall...

In the proposed experimental set-up, a photon travels toward a perfectly opaque wall up to 1.8 cm thick, and behind the wall is a photon detector. The wall is installed in the 0.28-meter-diameter bore of a 1.2-meter-diameter solenoid magnet that provides a very large field strength of 5 Tesla. The large field strength enhances the potential for detecting very low-mass particles such as MCPs as photons appear to pass through the wall.

First Simulation Of Quantum Tunnelling On A Quantum Computer - Technology Review

First Simulation Of Quantum Tunnelling On A Quantum Computer - Technology Review: The problem is the sheer complexity of these calculations, which require numerous quantum logic gates processing dozens of qubits. That's always been beyond the state-of-the-art for quantum computing.

Earlier this year, however, Andrew Sornborger at the University of Georgia in Athens showed how  the case of a single particle tunnelling through a barrier could be made simple enough to simulate on today's quantum computers. Such a demonstration would be the first example of a digital quantum simulation.

And today Guan Ru Feng and pals at Tsinghua University in Beijing say they've done it. To simulate tunnelling, these guys used a quantum computer that relies on nuclear magnetic resonance to manipulate qubits in encoded in the carbon and hydrogen atoms that make up chloroform molecules. They say this  is the first demonstration of a quantum tunnelling simulation using an NMR quantum computer.

Walk-Through-Wall Effect Might Be Possible With Humanmade Object, Physicists Predict

Walk-Through-Wall Effect Might Be Possible With Humanmade Object, Physicists Predict: ...Researchers would fashion the micrometer-wide trampoline out of graphene, a superstrong, superflexible sheet of carbon only one atom thick. They would suspend the membrane—small but much larger than the atoms and molecules that are the usual domain of quantum physics—over a metal plate. When experimenters applied an electrical voltage, the membrane would have two stable positions: one in which it bows slightly in the middle and one in which it bends enough to contact the plate below. In the Finnish team's design, the electrical and mechanical forces on the membrane create an energy barrier between these two positions. If researchers could lower the membrane's energy by cooling it to a temperature of less than a thousandth of a degree above absolute zero, then the only way it could get between the two positions is quantum tunneling. The experimenters could then observe the membrane's change of configuration by looking for a change in the system's capacitance, a measure of how well it can store electrical charge...