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Quantum logic clock

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Aquantum clockis a type ofatomic clockwithlaser cooledsingleionsconfined together in anelectromagnetic ion trap.Developed in 2010 by physicists at the U.S.National Institute of Standards and Technology,the clock was 37 times more precise than the then-existing international standard.[1]The quantum logic clock is based on an aluminium spectroscopy ion with a logic atom.

Both thealuminum-based quantum clock and themercury-based opticalatomic clocktrack time by the ion vibration at an optical frequency using aUV laser,that is 100,000 times higher than the microwave frequencies used inNIST-F1and other similar time standards around the world. Quantum clocks like this are able to befar more precisethan microwave standards.

Accuracy[edit]

ANIST2010 quantum logic clock based on a single aluminum ion

The NIST team are not able to measure clock ticks per second because the definition of a second is based on the standard NIST-F1, which cannot measure a machine more precise than itself. However, the aluminum ion clock's measured frequency to the current standard is1121015393207857.4(7) Hz.[2]NIST have attributed the clock's accuracy to the fact that it is insensitive to background magnetic and electric fields, and unaffected by temperature.[3]

In March 2008, physicists atNISTdescribed an experimental quantum logic clock based on individualionsofberylliumandaluminum.This clock was compared to NIST'smercuryion clock. These were the most accurate clocks that had been constructed, with neither clock gaining nor losing time at a rate that would exceed a second in over a billion years.[4]

In February 2010, NIST physicists described a second, enhanced version of the quantum logic clock based on individualionsofmagnesiumandaluminium.Considered the world's most precise clock in 2010 with a fractional frequency inaccuracy of8.6 × 10−18,it offers more than twice the precision of the original.[5] [6] In terms ofstandard deviation,the quantum logic clock deviates one second every 3.68 billion (3.68 × 109) years, while the then current international standard NIST-F1Caesium fountainatomic clock uncertainty was about 3.1 × 10−16expected to neither gain nor lose a second in more than 100 million (100 × 106) years.[7] [8]In July 2019, NIST scientists demonstrated such a clock with total uncertainty of9.4 × 10−19(deviates one second every 33.7 billion years), which is the first demonstration of a clock with uncertainty below10−18.[9][10][11]

Quantum time dilation[edit]

"Two clocks are depicted as moving in Minkowski space. ClockBis moving in a localized momentum wave packet with average momentum pB,while clockAis moving in a superposition of localized momentum wave packets with average momentum pAand p0A.ClockAexperiences a quantum contribution to the time dilation it observes relative to clockBdue to its nonclassical state of motion. "[12]

In a 2020 paper scientists illustrated that and how quantum clocks could experience a possibly experimentally testablesuperpositionof proper times via time dilation of the theory of relativity by which time passes slower for one object in relation to another object when the former moves at a higher velocity. In "quantum time dilation" one of the two clocks moves in a superposition of two localized momentumwave packets,[further explanation needed]resulting in a change to the classical time dilation.[13][14][12]

Other accurate experimental clocks[edit]

The accuracy of quantum-logic clocks was briefly superseded byoptical lattice clocksbased onstrontium-87andytterbium-171until 2019.[9][10][11]An experimental optical lattice clock was described in a 2014 Nature paper.[15] In 2015JILAevaluated the absolute frequency uncertainty of their lateststrontium-87429 THz (429228004229873.0 Hz[16]) optical lattice clock at2.1 × 10−18,which corresponds to a measurablegravitational time dilationfor an elevation change of 2 cm (0.79 in) on planet Earth that according to JILA/NIST FellowJun Yeis "getting really close to being useful forrelativistic geodesy".[17][18][19] At this frequency uncertainty, this JILA optical lattice optical clock is expected to neither gain nor lose a second in more than 15 billion (1.5 × 1010) years.[20]


See also[edit]

References[edit]

  1. ^Ghose, Tia (5 February 2010)."Ultra-Precise Quantum-Logic Clock Puts Old Atomic Clock to Shame".Wired.Retrieved2010-02-07.
  2. ^Rosenband, T.; Hume, D. B.; Schmidt, P. O.; Chou, C. W.; Brusch, A.; Lorini, L.; Oskay, W. H.; Drullinger, R. E.; Fortier, T. M.; Stalnaker, J. E.; Diddams, S. A.; Swann, W. C.; Newbury, N. R.; Itano, W. M.; Wineland, D. J.; Bergquist, J. C. (28 March 2008)."Frequency Ratio of Al+ and Hg+ Single-ion Optical Clocks; Metrology at the 17th Decimal Place"(PDF).Science.319(5871): 1808–1812.Bibcode:2008Sci...319.1808R.doi:10.1126/science.1154622.PMID18323415.S2CID206511320.Retrieved2013-07-31.
  3. ^"Quantum Clock Proves to be as Accurate as World's Most Accurate Clock".azonano. 7 March 2008.Retrieved2012-11-06.
  4. ^Swenson, Gayle (7 June 2010)."Press release: NIST 'Quantum Logic Clock' Rivals Mercury Ion as World's Most Accurate Clock".NIST.
  5. ^NIST's Second 'Quantum Logic Clock' Based on Aluminum Ion is Now World's Most Precise ClockArchived2010-09-05 at theWayback Machine,NIST, 4 February 2010
  6. ^ C.W Chou; D. Hume; J.C.J. Koelemeij; D.J. Wineland & T. Rosenband (17 February 2010)."Frequency Comparison of Two High-Accuracy Al+ Optical Clocks"(PDF).Physical Review Letters.104(7): 070802.arXiv:0911.4527.Bibcode:2010PhRvL.104g0802C.doi:10.1103/PhysRevLett.104.070802.PMID20366869.S2CID13936087.Retrieved9 February2011.
  7. ^"NIST's Second 'Quantum Logic Clock' Based on Aluminum Ion is Now World's Most Precise Clock"(Press release).National Institute of Standards and Technology.4 February 2010. Archived fromthe originalon 2010-09-05.Retrieved2012-11-04.
  8. ^"NIST-F1 Cesium Fountain Atomic Clock: The Primary Time and Frequency Standard for the United States".NIST.August 26, 2009.Retrieved2 May2011.
  9. ^abBrewer, S. M.; Chen, J.-S.; Hankin, A. M.; Clements, E. R.; Chou, C. W.; Wineland, D. J.; Hume, D. B.; Leibrandt, D. R. (2019-07-15)."Al + 27 Quantum-Logic Clock with a Systematic Uncertainty below 10 − 18".Physical Review Letters.123(3): 033201.arXiv:1902.07694.doi:10.1103/PhysRevLett.123.033201.PMID31386450.S2CID119075546.
  10. ^abWills, Stewart (July 2019)."Optical Clock Precision Breaks New Ground".
  11. ^abDubé, Pierre (2019-07-15)."Viewpoint: Ion Clock Busts into New Precision Regime".Physics.12:79.doi:10.1103/Physics.12.79.S2CID199119436.
  12. ^abSmith, Alexander R. H.; Ahmadi, Mehdi (23 October 2020)."Quantum clocks observe classical and quantum time dilation".Nature Communications.11(1): 5360.arXiv:1904.12390.Bibcode:2020NatCo..11.5360S.doi:10.1038/s41467-020-18264-4.ISSN2041-1723.PMC7584645.PMID33097702.Available underCC BY 4.0(some content of it has been used here).
  13. ^"Timekeeping theory combines quantum clocks and Einstein's relativity".phys.org.Retrieved10 November2020.
  14. ^O'Callaghan, Jonathan."Quantum Time Twist Offers a Way to Create Schrödinger's Clock".Scientific American.Retrieved10 November2020.
  15. ^Bloom, B. J.; Nicholson, T. L.; Williams, J. R.; Campbell, S. L.; Bishof, M.; Zhang, X.; Zhang, W.; Bromley, S. L.; Ye, J. (22 January 2014). "An optical lattice clock with accuracy and stability at the 10–18 level".Nature.506(7486): 71–5.arXiv:1309.1137.Bibcode:2014Natur.506...71B.doi:10.1038/s41586-021-04349-7.PMID24463513.S2CID4461081.
  16. ^Yasuda, Masami; Ido, Tetsuya."Report from TCTF/TCL JWG on Optical Frequency Metrology, TCTF Meeting, Delhi, India, 27 November 2017".APMP.Asia-Pacific Metrology Programme.Retrieved8 November2021.
  17. ^T.L. Nicholson; S.L. Campbell; R.B. Hutson; G.E. Marti; B.J. Bloom; R.L. McNally; W. Zhang; M.D. Barrett; M.S. Safronova; G.F. Strouse; W.L. Tew; J. Ye (21 April 2015)."Systematic evaluation of an atomic clock at 2 × 10−18total uncertainty ".Nature Communications.6:6896.arXiv:1412.8261.Bibcode:2015NatCo...6.6896N.doi:10.1038/ncomms7896.PMC4411304.PMID25898253.
  18. ^JILA Scientific Communications (21 April 2015)."About Time".Archived fromthe originalon 19 September 2015.Retrieved27 June2015.
  19. ^Laura Ost (21 April 2015)."Getting Better All the Time: JILA Strontium Atomic Clock Sets New Record".National Institute of Standards and Technology.Retrieved17 October2015.
  20. ^James Vincent (22 April 2015)."The most accurate clock ever built only loses one second every 15 billion years".The Verge.Retrieved26 June2015.
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