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Here\u2019s what you\u2019ll learn in this story:<\/p>\n
Atomic clocks will only see a loss of 1 second in accuracy over a period of 10 million years. They are used in multiple ways, including the GPS in your car.<\/p>\n
Now researchers have found a way to bypass the laws of quantum physics and create a vastly more stable and accurate atomic clock.<\/p>\n
In the future, such a device could let us accurately navigate an interstellar journey, or be a tool for predicting earthquakes or exploring dark matter more minutely.<\/p>\n
It\u2019s a beautiful, sunny day and you\u2019re cruising down the highway with the top down, taking directions from your phone\u2019s highly accurate GPS-enabled maps app. While these automated directions might appear effortless, they\u2019re actually the result of signals pinging satellites more than 12,000 miles above you.<\/p>\n
Inside each of these satellites is the thrumming heart of an atomic clock<\/a>.<\/p>\n Unlike the wall clocks you might find in your grandma\u2019s kitchen, atomic clocks keep time with extreme accuracy by tracking the movement of electrons within atoms. They measure the frequencies of the electromagnetic radiation needed to cause an electron to jump energy levels, or oscillate, inside atoms of elements like rubidium or strontium. While less precise clocks will experience a noticeable drift in accuracy over time<\/a>, an atomic clock will only see a loss of 1 second in accuracy over a period of 10 million years.<\/p>\n Future atomic clocks could be not only powerful tools for measuring time and navigating in far-off environments\u2014even interstellar space\u2014but for exploring fundamental scientific questions as well, like understanding dark matter or predicting when earthquakes will strike.<\/p>\n Yet, for all their strengths, scientists aren\u2019t yet satisfied with what atomic clocks can do. Researchers are working to develop atomic clocks that can be both more accurate and more portable. To achieve these goals, they\u2019re using techniques from quantum mechanics, the physics of the smallest particles of matter, atoms and subatomic particles.<\/p>\n \u201cAll these clocks are intrinsically quantum,\u201d said Vladan Vuleti\u0107<\/a>, PhD, professor of physics at MIT. This is because these systems are built around detecting and measuring the atomic\u2014and subatomic\u2014movement of atoms inside the clocks.<\/p>\n Two recent studies published in Nature<\/a> and Science Advances<\/a> explored quantum approaches that could improve the precision of atomic clocks. Vuleti\u0107 is senior author on the Nature research, which used methods from quantum<\/a> mechanics to improve the stability of atomic clocks in a subgenre of ultra-precise clocks called optical atomic clocks.<\/p>\n In these clocks, ytterbium atoms oscillate at even faster frequencies than standard atomic clocks, gaining the potential to measure intervals of time as small as 100 trillionth of a second.<\/p>\n But, their accuracy also makes them susceptible to quantum<\/a> distortions called \u201cnoise\u201d which make it difficult to measure the atoms\u2019 oscillations. You can think about this like running up against the \u201cquantum limit,\u201d Vuleti\u0107 said. This is the idea related to Heisenberg\u2019s Uncertainty Principle which dictates that there\u2019s a limit to how much you can know, or measure, a quantum system\u2014specifically, what physical properties of a particle you can measure. If you ascertain one property accurately, then you\u2019ll know the other property less accurately.<\/p>\n In their work, Vuleti\u0107 and colleagues demonstrated that entangling ytterbium atoms inside the clock with high oscillation frequency laser light makes it possible to eke out double the precision in their optical atomic clock.<\/p>\n \u201cIf you increase the number of particles, your precision gets better \u2026 [but] you always have a finite number of particles in the end,\u201d Vuleti\u0107 said. \u201cWith quantum mechanical [entanglement]… you can make future clocks that operate better for that given number of particles.\u201d Entanglement<\/a>, or correlation as some physicists would prefer to call it, is a quantum phenomenon where particles become connected to each other, even when they\u2019re great distances apart, such that measuring a property of one particle instantaneously changes a property of the other. This is what Einstein begrudgingly called \u201cspooky action at a distance.\u201d<\/p>\n Physicists from the University of Sydney in Australia have taken a different approach to this problem of overcoming the quantum limit. Their work published in Science Advances seems to\u2014but doesn\u2019t quite\u2014turn the rules of quantum mechanics on its head. In this work, the researchers have demonstrated a way to precisely measure both the position and momentum of a quantum system simultaneously while still keeping Heisenberg\u2019s Uncertainty Principle intact.<\/p>\n This is possible because the protocol focuses on measuring tiny changes with high levels of sensitivity while ignoring larger, \u201cglobal\u201d information about the system. The researchers compare this to trying to read an analog clock that only has a minute hand; you can know information about what minute it is very precisely, but information about what hour it is will be lost.<\/p>\n \u201cAnother way of explaining it is that we\u2019re actually throwing away information,\u201d said first author Christophe Valahu<\/a>, PhD. \u201cWe only care about very small changes, so that\u2019s how we\u2019re able to obtain this new uncertainty bound and kind of go around Heisenberg\u2019s Uncertainty Principle.\u201d<\/p>\n This work has a number of applications for improving quantum sensing, including improving the precision of atomic clocks, said senior author, Tingrei Tan<\/a>, PhD, in an email.<\/p>\n