- 2944 - ATOMIC CLOCKS - how accurate can they get? Our standard for timekeeping won’t change soon, but it is clear we can do better. At some point in the future, we will adopt a more accurate method. When we do, a clock based upon “quantum entanglement” could be the solution. If that’s the case, our official clocks will use “quantum weirdness to overcome quantum fuzziness“.
>>>>> The Covid 19 virus is just the most recent of a long line of viruses
>
> > > > This is deadly serious, so don't ignore it. Several
> > > > new viruses have been discovered and are wreaking
> > > > havoc throughout the national computer systems .
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> > > >THE AL GORE - DONALD TRUMP Virus ....
(Causes your computer to just keep counting and counting)
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> > > >THE CLINTON Virus ....
(Gives you a 7-Inch Hard Drive with NO memory)
-
> > > >THE BOB DOLE (aka: VIAGRA) virus...
(Makes a new hard drive out of an old floppy)
-
> > > >THE LEWINSKY virus...
(Sucks all the memory out of your computer,
then Emails everyone about what it did)
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> > > >THE RONALD REAGAN virus ....
(Saves your data, but forgets where it is stored)
-
> > > >THE MIKE TYSON virus ....
(Quits after two bytes)
-
> > > >THE OPRAH WINFREY virus ....
(Your 300 mb hard drive shrinks to 100 mb,
then slowly expands to restabilize around 200 mb)
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> > > >THE JACK KEVORKIAN virus...
(Deletes all old files)
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> > > >THE ELLEN DEGENERES virus...
(Disks can no longer be inserted)
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> > > >THE PROZAC virus...
(Totally screws up your RAM, but your processor doesn't care)
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> > > >THE ARNOLD SCHWARZENEGGER virus...
(Terminates some files, leaves, but will be back)
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> > > >THE LORENA BOBBITT virus...
(Reformats your hard drive into a 3.5 inch floppy,
then discards it through Windows)
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------------------ 2944 - ATOMIC CLOCKS - how accurate can they get?
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- Measuring time is about counting steps. Whether it’s the drip-drip of a water clock, the tic-toc of a mechanical clock, or the oscillating crystal of a quartz watch. Any accurate timepiece is built around counting the steps of something regular and periodic.
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- Nothing is perfectly regular, so no clock keeps perfect time, but our timepieces are getting very, very accurate. WOW! You can not believe how accurate?
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- Time has traditionally be measured in terms of astronomy, such as the rising and setting of the Sun, or the motion of the stars and Moon. There are have been several popular methods, but by the 1800s time was measured by what is known as the mean solar day.
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- A day isn’t always exactly 24 hours long. As the Earth moves along its elliptical orbit, its speed around the Sun changes slightly, making the day slightly longer or shorter depending on the season. But by taking the average of days over a year, astronomers could define a common standard.
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- As our mechanical clocks got more accurate, it became clear that the “mean solar day” was a problem. The rotation of the Earth isn’t constant enough. Changes in rotation due to tectonic shifts, and the gravitational dance the with Moon, the Earth rotates more slowly over time. So in 1956 time was defined in terms of the orbit of the Earth rather than its rotation.
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- An array of atomic clocks were used to keep time for the US Military. In 1967, we moved away from astronomy altogether when the length of a second was redefined in terms of an atomic clock.
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- The measured oscillation is based not on an atom, but the light emitted by an atom. Atoms create light when an electron moves from a higher energy state to a lower one. Since energy levels in an atom are quantized, light is emitted at a precise frequency.
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- In 1967 length of a second was set by defining a specific emission from Caesium-133 to be exactly 9,192,631,770 Hertz. This is the standard we still use today.
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- Although the modern standard is officially exact, it isn’t actually exact. Two atomic clocks of the same design keep slightly different times. By statistically comparing atomic clocks, we know they are accurate to about one second in thirty million years.
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- That’s probably accurate enough for everyday use, but it isn’t accurate enough for some scientific purposes. If we had more precise clocks, we could use them to study everything from geology to dark energy. So there is an ongoing quest to develop a new, more accurate standard.
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- Most of the approaches look toward purely optical methods, but new work in Nature uses atoms in quantum entanglement. One of the reasons modern atomic clocks aren’t perfect is that the atoms recoil when light is emitted, which shifts the frequency of emitted light slightly.
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- If the atom could be kept perfectly stationary when it emits light, then the frequency of the light would be exact. But quantum mechanics keeps the position of an atom a bit fuzzy, meaning that the frequency of emitted light is also a bit fuzzy. This effect is known as the “standard quantum limit“.
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- To address this problem, the team uses an effect known as quantum entanglement. By using lasers to squeeze atoms together, they can force the atoms to interact on a quantum level such that a measurement on one atom also measures all of them. Thus, the states of these atoms are entangled.
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- When another laser is used to trigger an atom into emitting light, a cascade occurs that syncs the atoms together. The light emitted is therefore much more precise than the standard quantum limit.
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- Statistical analysis of this new clock shows that it can function within an accuracy of 100 milliseconds over the age of the universe. Think about that. Over 14,000,000,000 years the time is accurate to within 100 milliseconds. The clock is so precise that it could test whether universal physical constants change over time.
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- Today our state-of-the-art atomic clocks are based on the precise detection of the energy difference between two atomic levels, measured as a quantum phase accumulated in a given time interval.
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- “Optical-lattice clocks” now operate at or near the “standard quantum limit” that arises from the quantum noise associated with discrete measurement outcomes.
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- While performance beyond the “standard quantum limit” has been achieved in microwave clocks and other atomic sensors by engineering quantum correlations (entanglement) between the atoms, the generation of entanglement on an optical-clock transition and operation of such a clock beyond the “standard quantum limit “represent major goals in quantum metrology that have never been demonstrated.
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- These results should be readily applicable to other systems, thus enabling further advances in timekeeping precision and accuracy.
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- Entanglement-enhanced “Optical-lattice clocks” will have many scientific and technological applications, including precision tests of the fundamental laws of physics, geodesy, or gravitational wave detection.
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---------------------- Other reviews available:
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- 2682 - ATOMIC CLOCKS - keep accurate time? This Review explains how atomic clocks keep time. It reviews the history of how these clocks were developed. It reviews fantastic facts that should amaze you. They are by far the most accurate instruments ever built.
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- December 19, 2020 ATOMIC CLOCKS 2944
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--------------------- --- Monday, December 21, 2020 ---------------------------
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