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Quantum logic clock
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<h2 id="accuracy">Accuracy</h2> <p>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 is 1121015393207857.4(7) Hz.<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a> NIST have attributed the clock's accuracy to the fact that it is insensitive to background magnetic and electric fields, and unaffected by temperature.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> </p><p>In March 2008, physicists at <a href="/facts/National_Institute_of_Standards_and_Technology/gr9Fnh85">NIST</a> described an experimental quantum logic clock based on individual <a href="/facts/Ion/3bePpDna">ions</a> of <a href="/facts/Beryllium_(element)/dv295voP">beryllium</a> and <a href="/facts/Aluminium/7wmR8jYE">aluminum</a>. This clock was compared to NIST's <a href="/facts/Mercury_(element)/WlxfoHva">mercury</a> ion 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.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> </p><p>In February 2010, NIST physicists described a second, enhanced version of the quantum logic clock based on individual <a href="/facts/Ion/3bePpDna">ions</a> of <a href="/facts/Magnesium/XyIhd2FG">magnesium</a> and <a href="/facts/Aluminium/7wmR8jYE">aluminium</a>. Considered the world's most precise clock in 2010 with a fractional frequency inaccuracy of 8.6 × 10−18, it offers more than twice the precision of the original.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> <a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> In terms of <a href="/facts/Standard_deviation/qSug9BRl">standard deviation</a>, the quantum logic clock deviates one second every 3.68 billion (3.68 × 109) years, while the then current international standard NIST-F1 <a href="/facts/Caesium_fountain/MgAauwom">Caesium fountain</a> atomic clock uncertainty was about 3.1 × 10−16 expected to neither gain nor lose a second in more than 100 million (100 × 106) years.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> <a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> In July 2019, NIST scientists demonstrated such a clock with total uncertainty of 9.4 × 10−19 (deviates one second every 33.7 billion years), which is the first demonstration of a clock with uncertainty below 10−18.<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a><a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a><a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> </p> <h2 id="quantum-time-dilation">Quantum time dilation</h2> <p>In a 2020 paper scientists illustrated that and how quantum clocks could experience a possibly experimentally testable <a href="/facts/Quantum_superposition/4z1UJg9o">superposition</a> of 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 momentum <a href="/facts/Wave_packet/4HLR2joo">wave packets</a>, resulting in a change to the classical time dilation.<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a><a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a><a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a> </p> <h2 id="other-accurate-experimental-clocks">Other accurate experimental clocks</h2> <p>The accuracy of quantum-logic clocks was briefly superseded by <a href="/facts/Atomic_clock/MF8nsXDR">optical lattice clocks</a> based on <a href="/facts/Isotopes_of_strontium/ljDHPVaV">strontium-87</a> and <a href="/facts/Ytterbium-171/76nIxUvr">ytterbium-171</a> until 2019.<a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a><a class="footnote-ref" id="fnref:16" href="#fn:16"><sup>16</sup></a><a class="footnote-ref" id="fnref:17" href="#fn:17"><sup>17</sup></a> An experimental optical lattice clock was described in a 2014 Nature paper.<a class="footnote-ref" id="fnref:18" href="#fn:18"><sup>18</sup></a> In 2015 <a href="/facts/JILA/5U4rzRvM">JILA</a> evaluated the absolute frequency uncertainty of their latest <a href="/facts/Isotopes_of_strontium/ljDHPVaV">strontium-87</a> 429 THz (429228004229873.0 Hz<a class="footnote-ref" id="fnref:19" href="#fn:19"><sup>19</sup></a>) optical lattice clock at 2.1 × 10−18, which corresponds to a measurable <a href="/facts/Gravitational_time_dilation/z4XG7SYA">gravitational time dilation</a> for an elevation change of 2 cm (0.79 in) on planet Earth that according to JILA/NIST Fellow <a href="/facts/Jun_Ye/wjqIwpvH">Jun Ye</a> is "getting really close to being useful for <a href="/facts/Geodesy/EJH0Te0m">relativistic geodesy</a>".<a class="footnote-ref" id="fnref:20" href="#fn:20"><sup>20</sup></a><a class="footnote-ref" id="fnref:21" href="#fn:21"><sup>21</sup></a><a class="footnote-ref" id="fnref:22" href="#fn:22"><sup>22</sup></a> 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.<a class="footnote-ref" id="fnref:23" href="#fn:23"><sup>23</sup></a> </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Atomic_clock/MF8nsXDR">Atomic clock</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Ghose, Tia (5 February 2010). "Ultra-Precise Quantum-Logic Clock Puts Old Atomic Clock to Shame". Wired. Retrieved 2010-02-07. <a href="https://wired.com/wiredscience/2010/02/quantum-logic-atomic-clock" target="_blank">https://wired.com/wiredscience/2010/02/quantum-logic-atomic-clock</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>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. PMID 18323415. S2CID 206511320. Retrieved 2013-07-31. <a href="http://tf.nist.gov/general/pdf/2280.pdf" target="_blank">http://tf.nist.gov/general/pdf/2280.pdf</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>"Quantum Clock Proves to be as Accurate as World's Most Accurate Clock". azonano.com. 7 March 2008. Retrieved 2012-11-06. <a href="http://www.azonano.com/news.asp?newsID=6031" target="_blank">http://www.azonano.com/news.asp?newsID=6031</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Swenson, Gayle (7 June 2010). "Press release: NIST 'Quantum Logic Clock' Rivals Mercury Ion as World's Most Accurate Clock". NIST. <a href="https://www.nist.gov/news-events/news/2008/03/nist-quantum-logic-clock-rivals-mercury-ion-worlds-most-accurate-clock-0" target="_blank">https://www.nist.gov/news-events/news/2008/03/nist-quantum-logic-clock-rivals-mercury-ion-worlds-most-accurate-clock-0</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>NIST's Second 'Quantum Logic Clock' Based on Aluminum Ion is Now World's Most Precise Clock Archived 2010-09-05 at the Wayback Machine, NIST, 4 February 2010 <a href="https://www.nist.gov/physlab/div847/logicclock_020410.cfm" target="_blank">https://www.nist.gov/physlab/div847/logicclock_020410.cfm</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>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. PMID 20366869. S2CID 13936087. Retrieved 9 February 2011. <a href="http://tf.boulder.nist.gov/general/pdf/2438.pdf" target="_blank">http://tf.boulder.nist.gov/general/pdf/2438.pdf</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>"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 from the original on 2010-09-05. Retrieved 2012-11-04. <a href="https://web.archive.org/web/20100905210116/http://www.nist.gov/physlab/div847/logicclock_020410.cfm" target="_blank">https://web.archive.org/web/20100905210116/http://www.nist.gov/physlab/div847/logicclock_020410.cfm</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>"NIST-F1 Cesium Fountain Atomic Clock: The Primary Time and Frequency Standard for the United States". NIST. August 26, 2009. Retrieved 2 May 2011. <a href="https://www.nist.gov/pml/div688/grp50/primary-frequency-standards.cfm" target="_blank">https://www.nist.gov/pml/div688/grp50/primary-frequency-standards.cfm</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>Brewer, 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. PMID 31386450. S2CID 119075546. <a href="https://link.aps.org/doi/10.1103/PhysRevLett.123.033201" target="_blank">https://link.aps.org/doi/10.1103/PhysRevLett.123.033201</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>Wills, Stewart (July 2019). "Optical Clock Precision Breaks New Ground". <a href="https://www.osa-opn.org/home/newsroom/2019/july/optical_clock_precision_breaks_new_ground/" target="_blank">https://www.osa-opn.org/home/newsroom/2019/july/optical_clock_precision_breaks_new_ground/</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>Dubé, Pierre (2019-07-15). "Viewpoint: Ion Clock Busts into New Precision Regime". Physics. 12: 79. doi:10.1103/Physics.12.79. S2CID 199119436. <a href="https://physics.aps.org/articles/v12/79" target="_blank">https://physics.aps.org/articles/v12/79</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>"Timekeeping theory combines quantum clocks and Einstein's relativity". phys.org. Retrieved 10 November 2020. <a href="https://phys.org/news/2020-10-timekeeping-theory-combines-quantum-clocks.html" target="_blank">https://phys.org/news/2020-10-timekeeping-theory-combines-quantum-clocks.html</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>O'Callaghan, Jonathan. "Quantum Time Twist Offers a Way to Create Schrödinger's Clock". Scientific American. Retrieved 10 November 2020. <a href="https://www.scientificamerican.com/article/quantum-time-twist-offers-a-way-to-create-schroedingers-clock/" target="_blank">https://www.scientificamerican.com/article/quantum-time-twist-offers-a-way-to-create-schroedingers-clock/</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> <li id="fn:14"><p>Smith, 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. ISSN 2041-1723. PMC 7584645. PMID 33097702. Available under CC BY 4.0 (some content of it has been used here). <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7584645" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7584645</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></p></li> <li id="fn:15"><p>Brewer, 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. PMID 31386450. S2CID 119075546. <a href="https://link.aps.org/doi/10.1103/PhysRevLett.123.033201" target="_blank">https://link.aps.org/doi/10.1103/PhysRevLett.123.033201</a> <a href="#fnref:15" class="footnote-back-ref">↩</a></p></li> <li id="fn:16"><p>Wills, Stewart (July 2019). "Optical Clock Precision Breaks New Ground". <a href="https://www.osa-opn.org/home/newsroom/2019/july/optical_clock_precision_breaks_new_ground/" target="_blank">https://www.osa-opn.org/home/newsroom/2019/july/optical_clock_precision_breaks_new_ground/</a> <a href="#fnref:16" class="footnote-back-ref">↩</a></p></li> <li id="fn:17"><p>Dubé, Pierre (2019-07-15). "Viewpoint: Ion Clock Busts into New Precision Regime". Physics. 12: 79. doi:10.1103/Physics.12.79. S2CID 199119436. <a href="https://physics.aps.org/articles/v12/79" target="_blank">https://physics.aps.org/articles/v12/79</a> <a href="#fnref:17" class="footnote-back-ref">↩</a></p></li> <li id="fn:18"><p>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. 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PMID 25898253. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4411304" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4411304</a> <a href="#fnref:20" class="footnote-back-ref">↩</a></p></li> <li id="fn:21"><p>JILA Scientific Communications (21 April 2015). "About Time". Archived from the original on 19 September 2015. Retrieved 27 June 2015. <a href="https://web.archive.org/web/20150919105141/https://jila.colorado.edu/news-highlights/about-time" target="_blank">https://web.archive.org/web/20150919105141/https://jila.colorado.edu/news-highlights/about-time</a> <a href="#fnref:21" class="footnote-back-ref">↩</a></p></li> <li id="fn:22"><p>Laura Ost (21 April 2015). "Getting Better All the Time: JILA Strontium Atomic Clock Sets New Record". National Institute of Standards and Technology. Retrieved 17 October 2015. <a href="https://www.nist.gov/pml/div689/20150421_strontium_clock.cfm" target="_blank">https://www.nist.gov/pml/div689/20150421_strontium_clock.cfm</a> <a href="#fnref:22" class="footnote-back-ref">↩</a></p></li> <li id="fn:23"><p>James Vincent (22 April 2015). "The most accurate clock ever built only loses one second every 15 billion years". The Verge. Retrieved 26 June 2015. <a href="https://www.theverge.com/2015/4/22/8466681/most-accurate-atomic-clock-optical-lattice-strontium" target="_blank">https://www.theverge.com/2015/4/22/8466681/most-accurate-atomic-clock-optical-lattice-strontium</a> <a href="#fnref:23" class="footnote-back-ref">↩</a></p></li> </ol>