precision time and frequency measurements and...

NIST Time and Frequency MetrologyNIST Time and Frequency Metrology

Precision Time and FrequencyPrecision Time and FrequencyMeasurements and Distribution:

PNT and Other ApplicationsMeasurements and Distribution:

PNT and Other ApplicationsPNT and Other Applications

T O’B i

PNT and Other Applications

T O’B iTom O’BrianChief, NIST Time and Frequency Division

and NIST Quantum Physics Division (JILA)

Tom O’BrianChief, NIST Time and Frequency Division

and NIST Quantum Physics Division (JILA)and NIST Quantum Physics Division (JILA)Boulder, Colorado

and NIST Quantum Physics Division (JILA)Boulder, Colorado

NIST Time and Frequency Metrology, Boulder, Colorado

PNTPNTtf.nist.govg

jila.colorado.edu

NIST Time and Frequency Metrology, Boulder, Colorado

Research, standards, and dissemination for precision timing

d h i ti

tf.nist.gov

and synchronization.

gjila.colorado.edu

NIST-F1 Atomic Fountain ClockPrimary Frequency Standard for the United States

“1 second is defined as the duration of 9,192,631,770 periods of the radiation corresponding to the gtransition between the two hyperfine levels of the ground state of the 133Cs atom.”

Current accuracy (uncertainty):

• 3 x 10-16 second.

NIST-F1 laser-cooled cesium f t i f t d d

• 25 trillionths of a second per day.

• 1 second in 100 million years.

fountain frequency standard“atomic clock”

Equivalent to measuring earth-sun distance (150,000,000 km) to uncertainty of about 45 m (less than thickness of human hair).

NIST Mercury Ion Clock and Aluminum Ion Logic ClockResearch Frequency Standards

• Research atomic clocks at NIST already at 8 x 10-18 uncertainty.• 1 second in 4 billion years.• Rapidly improving.

Equivalent to measuring earth-sun distance (150,000,000 km) to uncertainty of about 1 m (size of a bacterium).

Why worry about precision time and frequency metrology?

Impacts of Precise Timing and Synchronization

Telecommunication Networks

Synchronization to about 1 microsecond per day (10-11) for Stratum 1 telecommunicationstelecommunications.

Global wireline and wireless revenue in 2007: $1.65 trillion.Projected global wireline and wireless revenue in 2012: $2.3 trillion.

(2/3 of projected 2012 revenue in wireless systems)Source: Verizon

Electric Power Generation and Distribution


Synchronization to about 1 microsecond per day (10-11) for efficiency, fault location, etc.

US electric power sales in 2008: $360 billion.p $Smart Grid: Increased need for real-time, precision information on electric power generation, utilization, and distribution.

Source: US Energy Information Administration

Broad Range of Civilian/Commercial Global Navigation Satellite Systems Applications

SatelliteOperations

SatelliteOperations

AviationAviation

Surveying & MappingSurveying & MappingPrecision AgriculturePrecision Agriculture

CommunicationsCommunications

Power GridsPower GridsDisease ControlDisease Control

Personal NavigationPersonal Navigation

Trucking & Shipping

Trucking & Shipping

NavigationNavigation

Fishing &BoatingFishing &BoatingOil ExplorationOil Exploration

Global Navigation Satellite Systems (GNSS)


g y ( )

Civilian/commercial economic benefitsCivilian/commercial economic benefits estimated 2008:

US: $70 billionGlobal: $250 billion

New applications and impacts rapidly growing…growing…

N ti l it li ti “P i l ”National security applications: “Priceless”

Source: US National Executive Committee for Space-Based Positioning, Navigation, and Timing

Electronic Financial Transactions


• US Financial Industry Regulatory Authority (FINRA) rules for electronic financial transactions, reviewed and approved by US Securities Exchange Commission.pp y g

• Rules apply to more than 800,000 businesses conducting billions of transactions daily through New York Stock Exchange, NASDAQ, and other venues.

• All FINRA member electronic and mechanical time-stamping devices must remain accurate to within 1 second of NIST time.

• Hundreds of billions of dollars of daily electronic financial transactions in US• Hundreds of billions of dollars of daily electronic financial transactions in US.

• Hundreds of trillions of dollars of financial transactions per year in US.

Source: US Financial Industry Regulatory Authority

Science: Spacecraft Communications, Astrophysics


V L B li I t f tVery Long Baseline Interferometry

Timing/synchronization to asTiming/synchronization to as stringent as 1 picosecond per day (10-16).

NASA Deep Space Network

Source: NASA

Fundamental ScienceImpacts of Precise Timing and Synchronization

2

0

21RcGM

TT

)1( 20 Rc

GMT 22 cR

GM

2

2

0

1 v

TT

)2

1( 2

2

0 cvT cv

2c

Special and General Relativity and related phenomena…

Time-evolution of fundamental “constants”?

Superluminal neutrinos?

Fundamental Metrology: International System of Units (SI)Ti /f i t ill i t l ll th SI it


SI Base Unit Approximate Uncertainty in

Currently Depends on SI

Proposed SI Redefinition

Time/frequency impacts or will impact nearly all other SI units

Uncertainty in Current

Realization

Depends on SI Second

Redefinition2014

Second 10-15 Yes (no change)Second 10 Yes (no change)

Meter 10-12 Yes c (m / s) (no change)

Kilogram 10-9 h (J s)

Ampere 10-7 Yes e (A s)

Mole 10-7 NA

Kelvin 10-7 k (kg m2 / s2 / K)

Candela 10-3 Yes Kcd

(cd sr s3 / kg / m2)

• Precise timing and synchronization are a crucial part of the infrastructure of


Precise timing and synchronization are a crucial part of the infrastructure of modern technology.

U d ti l d lth h t i f th• Used continuously every day – although most users remain unaware of the use or impacts (part of the infrastructure).

• Needs of different users vary enormously – range of 1015 (fifteen orders of magnitude).

• Timestamping of electronic financial transactions – 1 second precision.p g p

• Global Navigation Satellite Systems applications – 10-15 second precision.

• NIST and other National Metrology Labs provide broad range of timing and synchronization measurement services to meet this very broad range of needs.

• Highest precision/accuracy for the most stringent requirements.

• Easiest use/lowest cost (free) for the broadest applications.

Improvements in Primary Frequency Standards10-9 10-910

10-10

10-11

10-10

10-11

NBS-160 Years of Progress in

Atomic ClocksNBS-2

10-12

10-13

10-12

10-13certa

inty

Atomic Clocks

NBS-5

NBS-4NBS-3

10

10-14

15

10

10-14

15ency

Unc

NIST-7NBS-6

NBS-5

10-15

10-16

10-15

10-16Freq

ue

NIST-F1Today

NIST-F1Initial

10-17

10-18

10-17

10-18

Why Improve Primary Frequency Standards?

1940 1950 1960 1970 1980 1990 2000 2010 2020Year


10-10

10-11

10-10

10-11Stratum 1 Telecomm

Needs as DeployedNBS-1

10-12

10-13

10-12

10-13certa

inty

10

10-14

15

10

10-14

15ency

Unc GNSS Current

GNSS Future10-15

10-16

10-15

10-16Freq

ue

VLBI/Deep Space/ Current NIST-F1

10-17

10-18

10-17

10-18

VLBI/Deep Space/Gravimetry, etc. Future

1940 1950 1960 1970 1980 1990 2000 2010 2020Year


10-10

10-11

10-10

10-11

Needs with ConservativeCalibration Uncertainty

NBS-1

10-12

10-13

10-12

10-13certa

inty Stratum 1 Telecomm

10

10-14

15

10

10-14

15ency

Unc

GNSS Current10-15

10-16

10-15

10-16Freq

ue

VLBI/Deep Space/ Current

GNSS Future NIST-F1

10-17

10-18

10-17

10-18

VLBI/Deep Space/ Current

VLBI/Deep Space/Gravimetry, etc. Future

1940 1950 1960 1970 1980 1990 2000 2010 2020Year

NIST Time and Frequency Standards and Distribution

Primary Frequency Standard andNIST Time ScaleNIST Time ScaleRealization of SI second

NIST-F1Hydrogen Maser &Measurement system

Time and


Frequency Distribution Services

Radio broadcasts Networks Satellites Noise metrology

Primary Frequency Standard andNIST Time ScaleNIST Time ScaleRealization of SI second


Time and




Primary Frequency Standard andNIST Time Scale


Realization of SI second

Research on Future St d dStandards and Distribution Mercury ion clock Neutral calcium

clockOptical frequency

synthesisQuantum computing

Two-way satellite time

NIST Time Scale and Distribution

Cesium Beam StandardsTwo-way satellite time & frequency transfer

H d M

UTC(NIST)

Hydrogen Masers

GPS

Measurement System

Calibrated by NIST-F1 primary frequency standard

International coordination of time and frequency: UTC, TAI, etc.

NIST Time and Frequency Metrology• NIST-F1 primary frequency standard periodically calibrates NIST time p y q y p y

scale.

• NIST-F1 also reports frequency information to BIPM, along with approximately 12 other primary frequency standards worldwide.pp y p y q y

• NIST time scale is the source of NIST’s realization of Coordinated Universal Time , UTC(NIST).

• NIST time scale reports time of day information to p yBIPM, along with approximately 60 other timing laboratories world-wide.

• The NIST time scale periodically calibrated by NIST-F1 is the• The NIST time scale, periodically calibrated by NIST-F1, is the ultimate source of all NIST time and frequency measurements.

• UTC, Coordinated Universal Time.

Time Scales

UTC, Coordinated Universal Time.

• Maintained by International Bureau of Weights and Measures (BIPM).

• Based on input from ~60 timing labs world-wide.

• ~400 atomic clocks total.

• Post-processed “paper” time scale.

Published monthly• Published monthly.

• Data are approximately 2 weeks to 6 weeks old.

• Local realizations/estimates of UTC.

• UTC(lab) – local estimate/realization of UTC.

• Usually real-time or near-real-time estimate.

• UTC(NIST) – real time estimate of UTC.

• UTC(USNO) – real time estimate of UTC• UTC(USNO) – real time estimate of UTC.

• GPS estimate of UTC. Very close (but not identical) to UTC(USNO).

NIST Time and Frequency Distribution

GPS – UTC(NIST)

T ~ ± 10 ns

UTC(NIST) compared to “GPS time” (GPS estimate of UTC) over 10 days.GPS estimate of UTC is very close to UTC(USNO).


GPS – UTC(NIST)

T ~ ± 10 ns

UTC(NIST) compared to “GPS time” (GPS estimate of UTC) over 200 days.GPS estimate of UTC is very close to UTC(USNO).

8


4

6

8UTC(USNO) - GPS

2

4

econ

ds

-2

0

Nan

ose

-6

-4

T ~ ± 5 ns-8

0 50 100 150 200Days

UTC(USNO) compared to “GPS time” (GPS estimate of UTC) over 180 days.

Days


NIST DO– UTC(NIST)By Common View GPSBy Common-View GPS

T ~ ± 0.5 ns

UTC(NIST) compared to NIST-Disciplined Oscillator linked to UTC(NIST) by Common View GPS. 100 days of data.

Serve the most demanding needs of timing


Serve the most demanding needs of timing laboratories, research laboratories, telecomm industry, etc.Provided remotely in the customer’s lab

Global Time Service• Calibrate remote clock with respect to NIST time via

Common View GPS

Provided remotely in the customer s lab.

Common-View GPS.• 10 ns uncertainty.

Frequency Measurement and Analysis Service

F ll (“bl k b ”) i h• Full measurement system (“black box”) with continuous remote monitoring by NIST.

• “In-house” f/f ~ 2 x 10-15.

• GPS transfer f/f ~ 2 x 10-13.

• SIM Time Network.SIM Time Network: International Time Coordination

• Pioneered by CENAM, NIST, NRC-Canada.• Based on NIST FMAS experience.

14 t t i N th C t l d S th• 14 current partners in North, Central, and South America.

• Additional partners planned.

• World’s only near real-time international measurement system.

World class international measurement system• World-class international measurement system available to broad range of national laboratories.

Real-time Comparison of NIST (USA) and CENAM (Mexico)

SIM Time Network: International Time Coordination

Real-time Comparison of NIST (USA) and CENAM (Mexico) Time Scales through SIM Network

Circular T data = BIPM realization

of UTC

Real-time international time scale competitive with post-processed BIPM UTC realization (up to several weeks late) with much simpler and less-expensive equipment.

• NIST Internet Time Service – time d d li d th I t t

NIST Time and Frequency Distribution10

codes delivered over the Internet via NTP (and other protocols).

• 8 billion automated synchs per day.4

6

8

f Dai

ly S

ynch

s

• Built into common operating systems: Windows, Mac, Linux, etc.

• 23 servers at 19 locations across 0

2

4

Billio

ns o

f

the US.

• Expected significant growth in need for auditable time-stamping at everExpected significant growth in need for auditable time stamping at ever greater timing precision.

NY Stock ExchangeNY Stock ExchangeAutomated Trading AnomalyMay 6, 2010

• Network Time Protocol (NTP).


Network Time Protocol (NTP).

• Computers exchange two-way messages over public or private network.

• Measures round-trip network delay.

• Algorithms for disciplining the system clock choosing optimalsystem clock, choosing optimal query interval, etc.

• Performance depends on symmetry of path delay.

• Almost always better than 50 ms performance.

• Usually better than 10 ms performance.

• “Best case” for distributed public network ~0.5 ms performance.

• ~ 1 s for limited private network under “ideal” conditions.

• Precision Time Protocol (PTP).


Precision Time Protocol (PTP).

• IEEE 1588-2008.

• Master/Slave timing.

• Multiple boundary clocks.

• Designed for sub-nanosecond timing, 10-11 frequency stability.g, q y y


Actual PTP performance. 4 different equipment manufacturers.

Time and




Primary Frequency Standard andNIST Time Scale


Realization of SI second

Research on Future St d dStandards and Distribution Mercury ion clock Neutral calcium

clockOptical frequency

synthesisQuantum computing

NIST-F1 Primary Frequency Standard

2.0NIST-F1 Frequency Uncertainty (In House)

1.5

Formal Evaluations reported to BIPM since Dec. 1999.

0-15

1.0

f/f

x 1

S 1 C0.0

0.5

51500 52000 52500 53000 53500 54000 54500 55000

Dec. 1999 Dec. 2009

NIST-F1 Cesium Fountain Standard

• 0.3 x 10-15 in house frequency uncertainty.

51500 52000 52500 53000 53500 54000 54500 55000

Modified Julian Date

q y y• 0.6 x 10-15 frequency uncertainty reported to BIPM.

10-9 10-9

Improvements in Primary Frequency Standards

10-10

10-11

10-10

10-11

NBS-1

10-12

10-13

10-12

10-13

certa

inty

10-14

10-15

10-14

10-15ency

Unc

NIST F110-16

10-17

10-16

10-17

Freq

ue

NIST-F2

NIST-F1

B d C i ?1940 1950 1960 1970 1980 1990 2000 2010 2020

10

10-18

10

10-18Beyond Cesium?

Year

f 11

Improvements in Primary Frequency Standards

Nff 11

0

Frequency uncertainty ~

f

= observation time510

150 10

1010

microwave

opticalf

fAtomic Resonance

N = number of atoms0 10microwavef

NIST research atomic clocks Al+ 1124 THz (1124 x 1012 Hz)Hg+ 1024 THzYb 520 TH OpticalYb 520 THzCa 456 THzSr 430 THz

Optical

Cs 0.0092 THz Microwave

Ultrastable Lasers

Q = 3 x 1015

Miniature ultrastable cavity Spectral hole burning

Potential for Q ~ 1017

Femtosecond Laser Frequency Combs: Key to Optical Clocks

Laser Frequency Comb: “Gears” of the Optical Clock

OpticalFrequency

1015 HStableLaser

Frequency~1015 HzLaserComb

105:1 Reduction

Not toScale!

MicrowaveStandards or Sources

101010 Hz

fs laserOptical ref 1 Optical ref 2

Femtosecond Laser Frequency Combs: Key to Optical Clocks

fs laser1 2

Compare 1 vs 2

Optical

set n = opt

Optical

m - opt2Optical

reference 1Optical

reference 2

0

set fo= 0

x2

Optical standards at NIST

Al+ (1124 THz), Hg+

(1064 THz) neutral Yb(1064 THz), neutral Yb(520 THz) and Ca (456 THz)

Direct comparison to Cs(0.0092 THz)

Improvements in Primary Frequency Standards: Optical Clocks10-9 10-9

10-10

10-11

10-10

10 11

OpticalFrequencyStandards

NBS-1

rtain

ty

10

10-12

10-11

10-12

(Research)

ency

Unc

e 10-13

10-14

10-13

10-14

Cesium MicrowavePrimary FrequencySt d d

Freq

ue

10-15

10-16

10-15

Standards

NIST-F1

10 16

10-17

10-16

10-17

NIST optical clocks

Year1940 1950 1960 1970 1980 1990 2000 2010 2020

10-1810-18

Optical Frequency Standards

f 11 b ti ti

Nff 11

0

Frequency uncertainty ~

= observation time

N = number of atoms

Perturbations:• Dephasing collisions.• Blackbody radiation.

• Magnetic fields.• Etc.y

Single Ions Cold Neutral Atomsg

Large Large N

Rare collisions Lattices to minimize lli icollisions

Well-controlled environment

More complex environment

NIST Single Ion Optical Frequency Standards

~8 x 10~8 x 10--1818~8 x 10~8 x 10--1818

Al+ quantum logic optical clock.

Si l H + iSingle Hg+ ion~1 x 10-17

Single mercury ion trap.

NIST Aluminum Ion “Logic Clock”1 Cool to zero motion quantum state

Be+

Al+

1. Cool to zero-motion quantum state with Be+ .

2. Depending on clock state, add

Linear Paul Trap

vibrational energy via Al+ .

3. Detect vibrational energy via Be+ .

0.6

0.7

0.8

0 1

0.12

0.14

27Al+ 1S0Mean = 1.3

27Al+ 3P0Mean = 6.9

0.4

0.5

Pro

babi

lity

0 06

0.08

0.1

obab

ility

0 1

0.2

0.3P

0.02

0.04

0.06

Pro 99.94% Detection fidelity

0 10 200

0.1

PMT counts0 10 20

0

Be+ photon counts

Al+ clock gravitational shift f/f = 8 x 10-18Al clock gravitational shift

Gravitational frequency shift near Earth surface ~1 x 10-18 / cm

Al+ clock gravitational shiftMeasure frequency shift by raising clock as little as 10 cm.Al clock gravitational shift

Measure frequency shift by moving Al+ ion as slowly asmoving Al+ ion as slowly as jogging speed (about 3 m/second).

Extreme precision optical clocks may initially be most useful asmay initially be most useful as exquisitely precise atomic sensors:• Gravity.• Magnetic fields.• Acceleration.• Temperature.

Oth titi• Other quantities…

NIST Optical Frequency Standards

Optical Lattice ClocksOptical Lattice Clocks

• Ytterbium (NIST)

• Strontium (JILA)

• ~1 x 10-17, rapidly improving

Improvements in Primary Frequency Standards: Optical Clocks10-9 10-9

10-10

10-11

10-10

10 11

OpticalFrequencyStandards

NBS-1

rtain

ty

10

10-12

10-11

10-12

(Research)

ency

Unc

e 10-13

10-14

10-13

10-14

B t

Freq

ue

10-15

10-16

10-15NIST-F1Best

Future10 16

10-17

10-16

10-17

NIST optical clocks

Future Clock???

Year1940 1950 1960 1970 1980 1990 2000 2010 2020

10-1810-18

Improvements in Frequency Standards and Clocks

NIST-F1

10-15 clocks (0.1/month)

10-13 clocks (10/month)

10-9 clocks (100,000/month)

10-11 clocks (1,000/month)

• Master clocks (long term synchronization)

• Secure communications

• Deep space

• Large scale communications systems

• Power grids• GPS Space Clocks

• Local communications hubs• Instrumentation level

flywheels

• Short haul navigation• Local communications

• Deep space navigation

• GPS Master clock (ground)

• GPS Space Clocks• Local synchronization

Opportunities for Improvement?

NIST Chip-Scale Atomic DevicesSensors Based on Atomic Frequency Metrology

1 mm

Chip-scale atomic clock

Chip-scale atomic magnetometer

Ultraminiature gyroscopegy p

Future atom-based sensors

NIST Chip-Scale Atomic Devices

Pea

Chip-scale atomic clocks:• f/f 10-11 or better

Chip-scale atomic clock Ultraminiature spectrometer

Related devices:• Ultraminiature spectrometer• f/f 10 11 or better.

• <100 mW power consumption.• Potential for low-cost mass production.

• Ultraminiature spectrometerfor telecommunications, chemical identification, atmospheric research, etc.

NIST chip-scale atomic device program since August 2004:

• Several NIST patents

Chip-scale atomic magnetometers:• 10-15 sensitivity: SQUID performance

with no cryogens.Several NIST patents.

• More than 100 NIST publications on chip-scale atomic devices.

• Dozens of conference and workshop presentations.

Ultraminiature NMR gyroscopes:• Navigation grade (0.002 degree).

Commercialization of Chip-Scale Atomic Devices

Symmetricom Chip-Scale Atomic ClockFi t i l hi l t i d iFirst commercial chip-scale atomic device

Introduced January 2011Other commercial products in development by p p y

several companies…

Aims to exceed Cesium beam clock performance for 1000× lower power10-9

CSAC

Research on Ultraminiature Cold Atom Clocks

DARPA IMPACT GoalsPower < 50 mW

Aims to exceed Cesium beam clock performance for 1000× lower power and size.

10-11

10-10 Block IIR RAFS IMPACT 5071A Beam Clock

zCSAC

Size 5 cc (total)

Timing 5 ns 10-12

y()

5071AUncertainty @ 1 day

10-14

10-135071A

IMPACT

Block IIR RAFS

100 101 102 103 104 105 106

t (s)

Sandia/JPL: Trapped 171Yb ionsOEWaves/Aerospace: Kerr optical frequency combsHoneywell:

Laser cooled Rb micro a e interrogationLaser-cooled Rb, microwave interrogationSymmetricom:NIST: Laser-cooled Rb, CPT interrogation

Research on Cold Atom GPS Clock

Source State Dielectric Loaded Ramsey Cavity

DetectionSelection Ramsey Cavity

Approximately same size as current GPS RAFS

Improvements in Time and Frequency DistributionI O ti lI O ti l

Fiber DistributionSystems

Fiber DistributionSystems

Ion OpticalClocks

Ion OpticalClocks

• High accuracy.Di t f f

Frequency CombsFrequency Combs

Future optical clocksf/f ~ 1x10-18

• Direct reference of optical applications to optical standards.

• New applications.

Optical Satellite Optical Satellite

• Directly compare optical frequencies spanning

pp

pDistributionpDistribution

gmore than an octave.

• Link optical to microwave frequencies.

Crucial topic… For another talk….

NIST Fiber Optic Time and Frequency Transfer

tf.nist.gov

Public, searchable database of Time & Frequency Division publications. >2 500 PDFs postedtf i t >2,500 PDFs posted.tf.nist.gov

Time and FrequencyResearch and

Time and FrequencyResearch and JILAJILAResearch and

Metrology in BoulderResearch and

Metrology in BoulderJILAJILA

NIST NIST BoulderBoulder

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