NIST:具有5.5 x 10^-19系统不确定性的高稳定性单离子钟(2025) 7页

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High-Stability Single-Ion Clock with 5.5×10
19
Systematic Uncertainty
Mason C. Marshall ,
1,*
Daniel A. Rodriguez Castillo ,
1,2
Willa J. Arthur-Dworschack ,
1,2
Alexander Aeppli ,
2,3
Kyungtae Kim ,
2,3
Dahyeon Lee ,
2,3
William Warfield ,
2,3
Joost Hinrichs ,
1,4
Nicholas V. Nardelli ,
1
Tara M. Fortier,
1
Jun Ye ,
2,3
David R. Leibrandt ,
1,2,5
and David B. Hume
1,2,
1
Time and Frequency Division, National Institute of Standards and Technology, Boulder, Colorado, USA
2
Department of Physics, University of Colorado, Boulder, Colorado, USA
3
JILA, National Institute of Standards and Technology and the University of Colorado, Boulder, Colorado, USA
4
Institute of Quantum Optics, Leibniz University Hannover, Hannover, Germany
5
Department of Physics and Astronomy, University of California, Los Angeles, California, USA
(Received 25 April 2025; accepted 17 June 2025; published 14 July 2025)
We report a single-ion optical atomic clock with a fractional frequency uncertainty of 5.5 × 10
19
and
fractional frequency stability of 3.5 × 10
16
=
ffiffiffiffiffiffi
τ=s
p
, based on quantum logic spectroscopy of a single
27
Al
þ
ion. A cotrapped
25
Mg
þ
ion provides sympathetic cooling and quantum logic readout of the
27
Al
þ1
S
0
3
P
0
clock transition. A Rabi probe duration of 1 s, enabled by laser stability transfer from a remote
cryogenic silicon cavity across a 3.6 km fiber link, results in a threefold reduction in instability compared to
previous
27
Al
þ
clocks. Systematic uncertainties are lower due to an improved ion trap electrical design,
which reduces excess micromotion, and a new vacuum system, which reduces collisional shifts. We also
perform a direction-sensitive measurement of the ac magnet ic field due to the rf ion trap, eliminating
systematic uncertainty due to field orientation.
DOI: 10.1103/hb3c-dk28
IntroductionOptical atomic clocks based on spectros-
copy of dipole-forbidden electronic transitions in isolated,
trapped atoms are among the most precise instruments
developed, capable of measuring time more precisely than
the cesium clocks that currently define the second [1].
Accordingly, optical clock frequency ratios are some of the
most accurate measurements [2,3] and are used as probes
for new physics [4], including time variation of funda-
mental constants [5,6]; violations of local position invari-
ance [7]; constraints on dark matter [2,8,9]; and general
relativity at small scales [10,11]. Optical clocks based on
single trapped ions [12,13] and neutral atoms in optical
lattices [14] have reached fractional frequency uncertainties
below 10
18
; further advances open new possibilities for
these investigations. Additionally, as the scientific com-
munity moves toward the redefinition of the second,
advances in the state of the art for clock accuracy and
stability are critical [15].
The exquisite degree of control and access to environ-
mentally insensitive transitions offered by trapped atomic
ions have made them a leading technology for measure-
ment accuracy. In particular, the
1
S
0
3
P
0
transition in
singly ionized aluminum offers a high transition frequency,
long excited-state lifetime, and one of the lowest known
sensitivities to blackbody radiation [1619]. In this Letter,
we report the accuracy and stability evaluation of the
current-generation
27
Al
þ
quantum logic clock at the
National Institute of Standards and Technology (NIST).
This clock realizes the lowest fractional frequency uncer-
tainty of any clock to date, at Δν=ν ¼ 5.5 × 10
19
. Its
fractional instability of 3.5 × 10
16
=
ffiffiffiffiffiffi
τ=s
p
represents a
threefold reduction in instability compared to the previous
NIST quantum logic clock [12]. Critical to these achieve-
ments are a more stable clock laser, an improved Paul trap
electrical design with reduced excess micromotion, and a
150× improvement in background gas pressure from a new
ultrahigh vacuum system.
Clock operation and stabilityThe operation of the
clock is similar to that described in [12,20]. The clock
cycle begins with preparation of the
27
Al
þ
clock ion into
one of the j
1
S
0
;m
F
¼5=2i states via optical pumping on
the
1
S
0
3
P
1
transition. Sympathetic cooling on the
25
Mg
þ
logic ion then brings the ion pair to the Doppler
temperature limit. Finally, we probe the
27
Al
þ
clock
transition using Rabi spectroscopy followed by quantum
logic readout [21,22].
We probe both the m
F
¼þ5=2 and m
F
¼ 5=2
1
S
0
3
P
0
transitions and generate a virtual first-order mag-
netic-field-insensitive transition from their mean frequency
[23]. Additionally, we alternate probing from opposite
directions, with the two probe beams counterpropagating
through the same single-mode optical fibers; the average of
opposite directions is insensitive to possible first-order
*
Contact author: mason.marshall@nist.gov
Contact author: david.hume@nist.gov
PHYSICAL REVIEW LETTERS 135, 033201 (2025)
Editors' Suggestion
0031-9007=25=135(3)=033201(6) 033201-1 © 2025 American Physical Society
资源描述:

本文介绍了一种单离子光原子钟,其频率不确定度为5.5×10⁻¹⁹,频率稳定性为3.5×10⁻¹⁶/√(τ/s)。该时钟基于单个²⁷Al⁺离子的量子逻辑光谱,通过共囚禁的²⁵Mg⁺离子提供协同冷却和量子逻辑读出。通过改进离子阱电气设计和新的真空系统,减少了系统误差。实验结果表明,该时钟的稳定性比以前的²⁷Al⁺时钟提高了三倍,代表了离子钟稳定性的新水平。 1. **时钟操作与稳定性** - 时钟周期包括光学抽运、协同冷却和拉比光谱探测。 - 通过激光稳定性传输和改进的时钟激光稳定化,实现了1秒的探测持续时间。 - 开发了全钛真空系统,减少了背景气体碰撞和氢化铝形成。 - 测量了时钟的稳定性,并与JILA Sr光学晶格钟进行了比较。 2. **系统误差评估** - 评估了相对论时间膨胀、二次塞曼、冷却激光斯塔克、黑体辐射、过量微运动、背景气体碰撞和一阶多普勒等系统误差。 - 通过改进离子阱电气设计和优化微运动补偿电压,减少了过量微运动的系统误差。 - 通过测量和拟合,确定了交流二次塞曼效应的大小和方向。 3. **结论** - 开发了一种²⁷Al⁺时钟,其稳定性为3.5×10⁻¹⁶/√(τ/s),不确定度为5.5×10⁻¹⁹。 - 稳定性比以前的铝离子钟提高了三倍,同时提高了光学时钟精度的技术水平。 - 稳定性可以通过更稳定的时钟激光或同时询问多个铝离子来进一步提高。 - 精度主要受多普勒温度测量的限制,低温系统可以降低背景气体碰撞和黑体辐射的不确定性。

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