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Stellar proof of 600 years of quantum law
In this section n LIGO prepares to peer into strange stars, page 11 n Mystery radiation hotspots could pose risk to air travellers, page 12 n Can some people with HIV really ditch condoms?, page 22
HONEYBEES may have a unique system for accepting migrants. “Drifting” bees that wander into a hive may stay – if the guard bees see fit. Such drift is common in apiaries, where hives are placed close together. A bee that drifts essentially migrates from its own hive to another, probably unintentionally. Morgane Nouvian and her team at the University of Queensland in Brisbane, Australia, reviewed 161 papers on how honeybees defend their hives to get an overview of the phenomenon. They report that 10 to 15 per cent of honeybees take on nest-guarding roles, usually when 2 to 3 weeks old. Their main role involves detecting and dealing with predators, but they are also the first point of contact when drifting bees arrive. In an inspection that can last half a minute, the guards check out chemical cues on the newcomer – typically hydrocarbons – that depend on hive-specific genetic factors and comb wax. If this profile matches or nearly matches that of their own hive, the guards will let the drifter in. Around 30 per cent of drifting bees are allowed to stay (Journal of Experimental Biology, doi.org/bx8q). A hive that is thriving is more welcoming, too. “It’s interesting that when there are enough resources, for instance nectar near the hive, and fewer empty combs, guards allow in more non-nestmates,” Nouvian says. There may not even be guards at the entrance in these circumstances. Scarcity can shut these “open borders” quickly. Guards not only reject newcomers at these times, but may even kill them, perhaps agitated by lack of food. The guards are also adept at spotting bees that aim to steal honey. “We know now that these robber bees are detected by their flight patterns and speed,” says Nouvian. “Guards can detect an incoming robber and sting it before it even reaches the nest.” Amitha Kalaichandran n
NARATHIP RUKSA/ALAMY
Beehives take in drifters in times of plenty
some unknown influence is allowing the particles to affect each other without breaking the principle of locality. To rule this out, Kaiser and his colleagues didn’t use any old random number generator to decide what to measure. After all, it’s even possible that the hidden variables could be tampering with the number generation itself. Instead, after the photons were shot towards the detectors, the researchers made a measurement of light from a randomly chosen star in the Milky Way. Its colour was what determined which photon property to measure. “If any physical mechanism –Entanglement is written in the stars– were to somehow jigger with the questions that get asked of each particle, those would have to have been put in motion at that star when it was about to emit that light that we measured,” Kaiser says. Light from the closest star OUR universe has been ruled by standard test for locality: Bell’s they used takes 600 years to weirdness for at least six centuries. inequality. It sets a limit on how reach us, so any hidden variables If the quantum effects in a new often two entangled particles can would have needed to be in play experiment aren’t genuine, end up in the same state just by since then. but are somehow caused by past chance – without quantum As in previous tests, Kaiser’s meddling, then that is how long mechanics or some unknown team found that their photons ago it must have happened – “hidden variables” to guide them. ended up correlated far too a finding that makes would-be The first step is to create a pair often, violating Bell’s inequality alternatives to quantum theory of entangled particles – often and supporting the non-local, even more unlikely. photons of light – then fire them quantum notion of reality Two qualities seem to describe off in different directions. Usually, (Physical Review Letters, doi.org/ our everyday world: realism, the a random number generator bzfh). idea that things have properties determines at the very last Of course, this loophole can which don’t vanish when we’re moment which property of each never really be closed. Maybe the not looking; and locality, which particle to measure. The detectors outcomes of these experiments means no influence can travel used are far enough apart that were determined by hidden faster than the speed of light. variables 700 years ago, or at the “These experiments make But the quantum effects we birth of the universe. But Kaiser alternative theories to see on tiny scales defy these and his colleagues plan to keep quantum mechanics far descriptions. The properties of using larger telescopes and more more implausible” particles aren’t set in stone until distant astronomical events to we measure them, and their states rule out the loophole as far back can be entangled – such that the arriving particles can’t “cheat” as they can. altering one affects the other and coordinate their states – “They’re making alternative much faster than light can travel unless they can signal each other theories to quantum mechanics between the two. faster than light. far more implausible – and they There are loopholes in If the measurements tally more were already implausible to start quantum theory, though. David often than allowed by Bell’s rule, with,” says Krister Shalm at the Kaiser at the Massachusetts then the particles aren’t governed National Institute of Standards Institute of Technology and his by locality. Previous experiments and Technologies in Boulder, colleagues are trying to close have shown this consistently, and Colorado. “This is just going that them down – aided by starlight. so backed quantum mechanics. extra step of pushing things Their experiment exploits a But it’s still dimly possible that back.” Leah Crane n
Stellar proof of 600 years of quantum law
11 February 2017 | NewScientist | 7
HONEYBEES may have a unique system for accepting migrants. “Drifting” bees that wander into a hive may stay – if the guard bees see fit. Such drift is common in apiaries, where hives are placed close together. A bee that drifts essentially migrates from its own hive to another, probably unintentionally. Morgane Nouvian and her team at the University of Queensland in Brisbane, Australia, reviewed 161 papers on how honeybees defend their hives to get an overview of the phenomenon. They report that 10 to 15 per cent of honeybees take on nest-guarding roles, usually when 2 to 3 weeks old. Their main role involves detecting and dealing with predators, but they are also the first point of contact when drifting bees arrive. In an inspection that can last half a minute, the guards check out chemical cues on the newcomer – typically hydrocarbons – that depend on hive-specific genetic factors and comb wax. If this profile matches or nearly matches that of their own hive, the guards will let the drifter in. Around 30 per cent of drifting bees are allowed to stay (Journal of Experimental Biology, doi.org/bx8q). A hive that is thriving is more welcoming, too. “It’s interesting that when there are enough resources, for instance nectar near the hive, and fewer empty combs, guards allow in more non-nestmates,” Nouvian says. There may not even be guards at the entrance in these circumstances. Scarcity can shut these “open borders” quickly. Guards not only reject newcomers at these times, but may even kill them, perhaps agitated by lack of food. The guards are also adept at spotting bees that aim to steal honey. “We know now that these robber bees are detected by their flight patterns and speed,” says Nouvian. “Guards can detect an incoming robber and sting it before it even reaches the nest.” Amitha Kalaichandran n
NARATHIP RUKSA/ALAMY
Beehives take in drifters in times of plenty
some unknown influence is allowing the particles to affect each other without breaking the principle of locality. To rule this out, Kaiser and his colleagues didn’t use any old random number generator to decide what to measure. After all, it’s even possible that the hidden variables could be tampering with the number generation itself. Instead, after the photons were shot towards the detectors, the researchers made a measurement of light from a randomly chosen star in the Milky Way. Its colour was what determined which photon property to measure. “If any physical mechanism –Entanglement is written in the stars– were to somehow jigger with the questions that get asked of each particle, those would have to have been put in motion at that star when it was about to emit that light that we measured,” Kaiser says. Light from the closest star OUR universe has been ruled by standard test for locality: Bell’s they used takes 600 years to weirdness for at least six centuries. inequality. It sets a limit on how reach us, so any hidden variables If the quantum effects in a new often two entangled particles can would have needed to be in play experiment aren’t genuine, end up in the same state just by since then. but are somehow caused by past chance – without quantum As in previous tests, Kaiser’s meddling, then that is how long mechanics or some unknown team found that their photons ago it must have happened – “hidden variables” to guide them. ended up correlated far too a finding that makes would-be The first step is to create a pair often, violating Bell’s inequality alternatives to quantum theory of entangled particles – often and supporting the non-local, even more unlikely. photons of light – then fire them quantum notion of reality Two qualities seem to describe off in different directions. Usually, (Physical Review Letters, doi.org/ our everyday world: realism, the a random number generator bzfh). idea that things have properties determines at the very last Of course, this loophole can which don’t vanish when we’re moment which property of each never really be closed. Maybe the not looking; and locality, which particle to measure. The detectors outcomes of these experiments means no influence can travel used are far enough apart that were determined by hidden faster than the speed of light. variables 700 years ago, or at the “These experiments make But the quantum effects we birth of the universe. But Kaiser alternative theories to see on tiny scales defy these and his colleagues plan to keep quantum mechanics far descriptions. The properties of using larger telescopes and more more implausible” particles aren’t set in stone until distant astronomical events to we measure them, and their states rule out the loophole as far back can be entangled – such that the arriving particles can’t “cheat” as they can. altering one affects the other and coordinate their states – “They’re making alternative much faster than light can travel unless they can signal each other theories to quantum mechanics between the two. faster than light. far more implausible – and they There are loopholes in If the measurements tally more were already implausible to start quantum theory, though. David often than allowed by Bell’s rule, with,” says Krister Shalm at the Kaiser at the Massachusetts then the particles aren’t governed National Institute of Standards Institute of Technology and his by locality. Previous experiments and Technologies in Boulder, colleagues are trying to close have shown this consistently, and Colorado. “This is just going that them down – aided by starlight. so backed quantum mechanics. extra step of pushing things Their experiment exploits a But it’s still dimly possible that back.” Leah Crane n
Stellar proof of 600 years of quantum law
11 February 2017 | NewScientist | 7