RADIOACTIVE waste has helped us peer inside a star explosion and solve a long-standing mystery about the cosmic origins of chemical elements.

Stars fuse hydrogen in their cores, creating helium and releasing energy. As they run out of hydrogen fuel, very massive stars start fusing heavier elements. Eventually, the star’s core becomes so massive that it collapses, triggering a brilliant explosion that tears the star apart and flings material into space. This process is what seeds the universe with heavy elements important for life.

“Core-collapse supernovae are truly the factories of element production and are largely responsible for producing many of the elements we take for granted in our everyday lives,” says at the University of Notre Dame in Indiana.

At first, the blast wave rips atoms apart, making a hot mix of fundamental particles. These particles then recombine to form a range of elements, including some radioactive versions that decay into more stable substances. Studying what emerges from a supernova and the rates at which different elements decay or get altered by high-speed collisions can help us understand the underlying physics of a star explosion.

One of the best clues is titanium-44, which is made naturally only by supernovae. When observed with space probes, titanium-44 produces a very clear signal in supernova remnants – but there is a catch. All observations to date have shown much more titanium-44 than our best models predict. This may be because reactions in the debris that destroy the element have been poorly understood.

To help solve the riddle, at the University of Edinburgh, UK, and his colleagues looked to a novel source of titanium: irradiated parts removed from a particle accelerator. The scrap metal, from the in Villigen, Switzerland, contained enough titanium-44 for the team to run an experiment.

“We are the only group worldwide which can provide the needed amount of the material in the required chemical form,” says Maria Dorothea Schumann at the Paul Scherrer Institute. “Accelerator components represent a new and unique resource for harvesting such valuable material.”

Murphy’s team used the scrap metal to produce a beam of titanium-44 in an accelerator at CERN in Switzerland, and sent the beam into a helium-filled gas chamber. The experiment recreated the explosive energy of a supernova to see how quickly titanium-44 is destroyed by collisions with helium, a known process in supernova remnants.

“What we’ve found is that the rate of that reaction is less than half of what was previously thought,” says Murphy. Models predict at least 30 per cent less titanium-44 than a supernova actually makes, but the finding boosts the amount left behind (Physics Letters B, ).

“This brings the observation and models into much closer agreement,” says Murphy.

This article appeared in print under the headline “Scrap metal solves cosmic conundrum”

Atom lasers emit beams of matter instead of photons. This is possible using an ultra-cold gas called a Bose-Einstein condensate, which makes millions of atoms behave like a single wave. Previous work created atom lasers by bottling up the ultra-cold gas using powerful electromagnets.

“It acts like a thermos flask, confining the atoms and keeping them from heating up,” explains at the Institute of Electronic Structure and Laser in Hellas, Greece. Physicists can then guide a beam of atoms out of the “bottle” using radio waves.

But the radio waves used in the past were relatively weak, limiting the power of atom lasers. Von Klitzing and his team found a way to use stronger radio waves, boosting the flow to 10⁸ atoms per second. That is 16 times as powerful as the previous best atom laser, the team claims.

Fuzzy laser

Von Klitzing hopes to use such a laser on , a mission now under consideration at the European Space Agency. The mission’s spacecraft will use a high-precision atom laser to look for the effects of something called loop quantum gravity. Finding such effects could help unite Einstein’s general theory of relativity – our best description of gravity – with the world of tiny particles described by quantum mechanics.

While in orbit, STE-QUEST will fire its atom laser, split it in two, then recombine the beams. General relativity has it that space-time is a smooth fabric, but mathematical theories of quantum gravity say that at very small scales, space-time should be grainy. If these grains exist, the split beams would travel through different sets of them, which would affect the way the laser looks when it is recombined.

“What we expect to find is that the final beam will be fuzzy, de-coherent, unlike what it was before it was split into two,” says Bob Bingham at the in Oxfordshire, UK, who is part of STE-QUEST but not on von Klitzing’s team.

STE-QUEST is up against several other proposed missions and must compete for an ESA launch. Although it was not selected during ESA’s latest round of mission evaluations, the project is still very active and will be in the next batch of mission ideas up for consideration, says Gerald Hechenblaikner of international group , who has been asked by ESA to assess STE-QUEST.

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Each fruit of the barberry, Berberis vulgaris, has either one or two seeds, which may be targeted by larvae of the tephritid fruit fly.

, now at the University of Göttingen, Germany, and her colleagues collected around 2000 berries and examined them for signs of piercing – because the fruit fly makes a tiny hole in the berries so it can lay its eggs inside. If the berries were pierced, the team also dissected them.

It was already known that the plant can cut off nutrient supplies to its seeds when resources are limited. Meyer’s team also found that the same mechanism was used with infested seeds, killing the parasite in the process. More surprisingly, the likelihood of a seed being aborted depended on how many seeds the berry had – if it had two seeds and one was attacked, the plant killed off the infested seed 75 per cent of the time, compared with just 5 per cent in single-seeded berries that were attacked.

This response makes reproductive sense. Aborting an infested seed in two-seeded fruits might save the other one and keep the fruit fertile. But if there is only one seed, killing it would render the fruit sterile, and it might be better instead to rely on the small chance that the parasite dies naturally.

Such a sophisticated response in plants is impressive, says Susan Dudley of McMaster University in Hamilton, Ontario, Canada. “I think it is a cool result.”

Some plants were known to try to ward off infections by varying their defences with the time of day, but the new finding trumps that in terms of behavioural complexity, she says: “responses depend on both the number of seeds and infection by parasites, with response to one affected by the state of the other.”

Journal reference: American Naturalist:

For years physicists have been smashing distance records for quantum teleportation, which exploits quantum entanglement to send encrypted information. Entangled particles remain linked no matter how far apart they are, and a change to one particle always affects its partner in a particular way. In experiments, for example, a pair of entangled particles is separated and each partner is sent to a different location. When someone measures the particle at point A, its quantum state is decided and that event immediately causes a corresponding change in the particle at point B.

No physical matter is transmitted, and nothing is travelling faster than light. But the person at point B can recreate the photon at point A using only information about the observed changes – effectively teleporting the photon.

Physicists have done this with light and with matter, such as entangled ions. But of Tohoku University in Sendai, Japan, wondered if it would be possible to also teleport quantum energy.

Quantum toothpaste

Theory has it that a vacuum is not truly empty – it is constantly roiling with tiny fluctuations that cause particles to pop in and out of existence. These particles pop up in entangled pairs and, crucially, the two partners can appear great distances apart.

The quantum field in the vacuum of space is usually at its lowest energy level. But if someone measures the field, the quantum system in that region – let’s call it region A – is disturbed and becomes excited, gaining energy. Hotta suggests using the information gained from that measurement to create an electric current that is tuned to the quantum change. Because particles spread across the vacuum are entangled with each other, sending the current through another part of the vacuum – region B – will allow the current to extract energy from the quantum field in that region. In other words, particles from region A will teleport some of their energy to region B, without the need for a physical transmission line.

“A measurement made at point A provides the information needed to unlock hidden energy at point B,” says , a physicist at the Massachusetts Institute of Technology, who was not involved in the research. But Hotta’s original theory suggested energy teleportation would work only over a few tens of nanometres.

Light work

To get greater reach, Hotta and his colleagues have now applied a twist to their theory that adds squeezed light to the vacuum. In quantum mechanics, there is a limit to how precisely we can know multiple values in a physical system. Physicists can exploit this effect by increasing the uncertainty of one value on purpose, allowing them to better pin down a different target property.

“Like toothpaste, if you make the tube smaller in one part, it gets bigger in another direction,” says at the University of British Columbia in Vancouver, Canada, who did not take part in the study.

Normally, photons travelling through a vacuum arrive randomly. Reducing uncertainty in the light’s amplitude, which is proportional to the number of photons travelling together, forces more of its photons to travel in pairs. When this squeezed light is sent through the space between two targeted regions, it enhances the entanglement between those regions, so that energy can be extracted across greater distances, says Hotta.

Cooler computing

Entanglement is also fundamental to quantum computers, which promise faster processing speeds by replacing binary 1s and 0s, used to store information in standard computers, with qubits that can be both 1 and 0 simultaneously. But even qubits need a power source to operate, and right now that comes from electrical current running through a quantum chip, which gives off waste heat as it travels that can destroy the fragile state of entanglement. By replacing electrical wiring with teleported quantum energy, qubits could safely maintain their entanglement, says Hotta.

The amount of energy teleported would still be very small – about several hundred microelectronvolts – so even though it should work over greater distances, it is more likely that Hotta’s teleportation technique will only be useful for now in quantum chips that send energy over a few hundred micrometres.

In principle, though, quantum energy teleportation could one day be useful to much larger machines, says Lloyd: “While it currently seems unlikely that one could power a spaceship, or even a desk light, by quantum energy teleportation, you never know.”

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