Computer and AI giant rolls out machine using ‘Heron’ chips using subatomic particles instead of ones and zeros.
Category: quantum physics – Page 410
Fractal photonic anomalous Floquet topological insulators to generate multiple quantum chiral edge states
An anomalous Floquet topological insulator (AFTI) is a periodically driven topological insulator (TI with nonzero winding numbers to support topological edge modes, though its standard topological invariants like Chern numbers are zero.
The photonic lattice constructed by an optical waveguide array fabricated by the femtosecond laser direct writing (FLDW) is an important platform for quantum simulation to realize photonic AFTIs, because the FLDW offers flexible design of true three-dimensional (3D) waveguide structures and precise control of each coupling between waveguides. Moreover, the evolution distance of the lattice can be mapped as the evolution time.
In femtosecond-laser-direct-written photonic AFTIs, selective coupling of adjacent waveguides in a cycle is explicitly defined by the discrete periodically driving protocol. At the complete transfer discrete driving protocol, chiral edge modes co-exist with dispension-less bulk modes, and the lattice energy transfer efficiency of the chiral edge mode is the highest among all TIs (close to 100%), so it is very suitable for the transport of fragile quantum states.
Polaritons open up a new lane on the semiconductor highway
On the highway of heat transfer, thermal energy is moved by way of quantum particles called phonons. But at the nanoscale of today’s most cutting-edge semiconductors, those phonons don’t remove enough heat. That’s why Purdue University researchers are focused on opening a new nanoscale lane on the heat transfer highway by using hybrid quasiparticles called “polaritons.”
Thomas Beechem loves heat transfer. He talks about it loud and proud, like a preacher at a big tent revival.
“We have several ways of describing energy,” said Beechem, associate professor of mechanical engineering. “When we talk about light, we describe it in terms of particles called ‘photons.’ Heat also carries energy in predictable ways, and we describe those waves of energy as ‘phonons.’ But sometimes, depending on the material, photons and phonons will come together and make something new called a ‘polariton.’ It carries energy in its own way, distinct from both photons or phonons.”
Time’ May Explain Why Gravity Won’t Play by Quantum Rules
A new theory suggests that the unification between quantum physics and general relativity has eluded scientists for 100 years because huge “fluctuations” in space and time mean that gravity won’t play by quantum rules.
Since the early 20th century, two revolutionary theories have defined our fundamental understanding of the physics that governs the universe. Quantum physics describes the physics of the small, at scales tinier than the atom, telling us how fundamental particles like electrons and photons interact and are governed. General relativity, on the other hand, describes the universe at tremendous scales, telling us how planets move around stars, how stars can die and collapse to birth black holes, and how galaxies cluster together to build the largest structures in the cosmos.
Quantum ‘magic’ could help explain the origin of spacetime
A quantum property dubbed “magic” could be the key to explaining how space and time emerged, a new mathematical analysis by three RIKEN physicists suggests. The research is published in the journal Physical Review D.
It’s hard to conceive of anything more basic than the fabric of spacetime that underpins the universe, but theoretical physicists have been questioning this assumption. “Physicists have long been fascinated about the possibility that space and time are not fundamental, but rather are derived from something deeper,” says Kanato Goto of the RIKEN Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS).
This notion received a boost in the 1990s, when theoretical physicist Juan Maldacena related the gravitational theory that governs spacetime to a theory involving quantum particles. In particular, he imagined a hypothetical space—which can be pictured as being enclosed in something like an infinite soup can, or “bulk”—holding objects like black holes that are acted on by gravity. Maldacena also imagined particles moving on the surface of the can, controlled by quantum mechanics. He realized that mathematically a quantum theory used to describe the particles on the boundary is equivalent to a gravitational theory describing the black holes and spacetime inside the bulk.
Wormholes help resolve black hole information paradox
A RIKEN physicist and two colleagues have found that a wormhole—a bridge connecting distant regions of the Universe—helps to shed light on the mystery of what happens to information about matter consumed by black holes.
Einstein’s theory of general relativity predicts that nothing that falls into a black hole can escape its clutches. But in the 1970s, Stephen Hawking calculated that black holes should emit radiation when quantum mechanics, the theory governing the microscopic realm, is considered. “This is called black hole evaporation because the black hole shrinks, just like an evaporating water droplet,” explains Kanato Goto of the RIKEN Interdisciplinary Theoretical and Mathematical Sciences.
This, however, led to a paradox. Eventually, the black hole will evaporate entirely—and so too will any information about its swallowed contents. But this contradicts a fundamental dictum of quantum physics: that information cannot vanish from the Universe. “This suggests that general relativity and quantum mechanics as they currently stand are inconsistent with each other,” says Goto. “We have to find a unified framework for quantum gravity.”
Resolving the black hole ‘fuzzball or wormhole’ debate
Black holes really are giant fuzzballs, a new study says.
The study attempts to put to rest the debate over Stephen Hawking’s famous information paradox, the problem created by Hawking’s conclusion that any data that enters a black hole can never leave. This conclusion accorded with the laws of thermodynamics, but opposed the fundamental laws of quantum mechanics.
“What we found from string theory is that all the mass of a black hole is not getting sucked in to the center,” said Samir Mathur, lead author of the study and professor of physics at The Ohio State University. “The black hole tries to squeeze things to a point, but then the particles get stretched into these strings, and the strings start to stretch and expand and it becomes this fuzzball that expands to fill up the entirety of the black hole.”
Physicists ‘entangle’ individual molecules for the first time, hastening possibilities for quantum computing
For the first time, a team of Princeton physicists have been able to link together individual molecules into special states that are quantum mechanically “entangled.” In these bizarre states, the molecules remain correlated with each other—and can interact simultaneously—even if they are miles apart, or indeed, even if they occupy opposite ends of the universe. This research was recently published in the journal Science.
“This is a breakthrough in the world of molecules because of the fundamental importance of quantum entanglement,” said Lawrence Cheuk, assistant professor of physics at Princeton University and the senior author of the paper. “But it is also a breakthrough for practical applications because entangled molecules can be the building blocks for many future applications.”
These include, for example, quantum computers that can solve certain problems much faster than conventional computers, quantum simulators that can model complex materials whose behaviors are difficult to model, and quantum sensors that can measure faster than their traditional counterparts.
Might There Be No Quantum Gravity After All?
A proposed model unites quantum theory with classical gravity by assuming that states evolve in a probabilistic way, like a game of chance.
Physicists’ best theory of matter is quantum mechanics, which describes the discrete (quantized) behavior of microscopic particles via wave equations. Their best theory of gravity is general relativity, which describes the continuous (classical) motion of massive bodies via space-time curvature. These two highly successful theories appear fundamentally at odds over the nature of space-time: quantum wave equations are defined on a fixed space-time, but general relativity says that space-time is dynamic—curving in response to the distribution of matter. Most attempts to solve this tension have focused on quantizing gravity, with the two leading proposals being string theory and loop quantum gravity. But new theoretical work by Jonathan Oppenheim at University College London proposes an alternative: leave gravity as a classical theory and couple it to quantum theory through a probabilistic mechanism [1].