Einstein’s “spooky action at a distance” can reach as far as low earth orbit, and twisted light could boost quantum communication bandwidth.
Researchers from the University Of New South Wales(UNSW) in Australia have successfully demonstrated that they can write and control the quantum version of computer code on a silicon microchip. Computers, at the moment, use binary language to operate, 0 and 1. Together, these two bits generate code words that can be used to program complex commands. But in quantum computing language there’s also the option for bits to be in superposition, what this actually means is that they can be 1 and 0 at the very exact same time. This unlocks a massively more powerful programming language, but until now scientists haven’t been able to figure out how to write it.
A beam splitter is placed in a quantum superposition state of being both active and inactive allowing the wave and particle aspects of the system to be observed in a single setup.
Entanglement between distant quantum objects is an important ingredient for future information technologies. Researchers at the ETH have now developed a method with which such states can be created a thousand times faster than before.
If a time traveler went back in time and stopped their own grandparents from meeting, would they prevent their own birth?
That’s the crux of an infamous theory known as the ‘grandfather paradox’, which is often said to mean time travel is impossible — but some researchers think otherwise. A group of scientists have simulated how time-travelling photons might behave, suggesting that, at the quantum level, the grandfather paradox could be resolved.
The research was carried out by a team of researchers at the University of Queensland in Australia and their results are published in the journal Nature Communications. The study used photons — single particles of light — to simulate quantum particles travelling back through time. By studying their behavior, the scientists revealed possible bizarre aspects of modern physics.
A research group at Osaka University has succeeded in observing at the intended timing two-phonon quantum interference by using two cold calcium ions in ion traps, which spatially confine charged particles. A phonon is a unit of vibrational energy that arises from oscillating particles within crystals. Two-particle quantum interference experiments using two photons or atoms have been previously reported, but this group’s achievement is the world’s first observation using two phonons.
This group demonstrated that the phonon, a quantum mechanical description of an elementary vibrational motion in matter, and the photon, an elementary particle of light, share common properties. This group’s research results will contribute to quantum information processing research, including quantum simulation using phonons and quantum interface research.
Ion traps are an important technique in physically achieving quantum information processing including quantum computation, and research on ion traps is being carried out all over the world, with Dr. David J. Wineland of the United States, a leading expert in the field, winning the Nobel Prize in Physics in 2012.
‘In a nice piece of “spin-off science” from this technological achievement, we were able to perform a “Bell test”, by first using the high-precision logic gate to generate an entangled state of the two different-species ions, then manipulating and measuring them independently. This is a test which probes the non-local nature of quantum mechanics; that is, the fact that an entangled state of two separated particles has properties that cannot be mimicked by a classical system. This was the first time such a test had been performed on two different species of atom separated by many times the atomic size.’
While Professor Lucas cautions that the so-called ‘locality loophole’ is still present in this experiment, there is no doubt the work is an important contribution to the growing body of research exploring the physics of entanglement. He says: ‘The significance of the work for trapped-ion quantum computing is that we show that quantum logic gates between different isotopic species are possible, can be driven by a relatively simple laser system, and can work with precision beyond the so-called “fault-tolerant threshold” precision of approximately 99% — the precision necessary to implement the techniques of quantum error correction, without which a quantum computer of useful size cannot be built.’
In the long term, it is likely that different atomic elements will be required, rather than different isotopes. In closely related work published in the same issue of Nature, by Ting Rei Tan et al, the NIST Ion Storage group has demonstrated a different type of quantum logic gate using ions of two different elements (beryllium and magnesium).
German quantum gravity expert Sabine Hossenfelder is fighting in the battle over theoretical physics, a clash between those looking for evidence and those looking to move forward faster.
As conventional computers draw ever closer to their theoretical limit, the race is on to build a machine that can truly harness the unprecedented processing power of quantum computing. And now two research teams have independently demonstrated how entangling atoms from different elements can address the problem of quantum memory errors while functioning within a logic gate framework, and also pass the all-important test of true entanglement.
Physicists at the National Institute of Standards and Technology (NIST) have added to their collection of ingredients for future quantum computers by performing logic operations—basic computing steps—with two atoms of different elements. This hybrid design could be an advantage in large computers and networks based on quantum physics.
The NIST experiment, described in the Dec. 17 issue of Nature, manipulated one magnesium and one beryllium ion (charged atom) confined in a custom trap (see photo). The scientists used two sets of laser beams to entangle the two ions—establishing a special quantum link between their properties—and to perform two types of logic operations, a controlled NOT (CNOT) gate and a SWAP gate. The same issue of Nature describes similar work with two forms of calcium ions performed at the University of Oxford.
“Hybrid quantum computers allow the unique advantages of different types of quantum systems to be exploited together in a single platform,” said lead author Ting Rei Tan. “Many research groups are pursuing this general approach. Each ion species is unique, and certain ones are better suited for certain tasks such as memory storage, while others are more suited to provide interconnects for data transfer between remote systems.”
