Radiometry from Watts to Single-Photons

Bridging the Gap: Radiometry from Watts to Single-Photons

A. Migdall B. Calkins D. Livigni C. Cromer R. P. Mirin M. Dowell S. W. Nam J. Fan S. V. Polyakov T. Gerrits M. Stevens J. Lehman N. Tomlin A. Lita I. Vayshenker

NIST, Boulder & Gaithersburg

NEWRAD Maui, HI Sept. 22, 2011 Outline

• Existing Radiometry and The Gap

(What this talk is and is not about)

• Bridging the Gap efforts (review)

• Hope: Single-Photon Tools

• Issues and concerns

Bridging the Gap Absolute Radiometric Standards Sources Detectors Blackbody Trap: Radiometer

T Electrical Substitution Temperature Radiance Radiant power

Synchrotron e- Trap: B-field Semiconductor

Radiant power (transfer standard) B-field, current, energy Radiance Radiometry Electrical Substitution Radiometry

High-Accuracy Laser Cryogenic Optimized Radiometer Cryogenic (HACR) 1980s Radiometer (LOCR) 1990s

From NIST Technical Note 1421, A. Parr

Optical Power = Electrical Power

Bridging the Gap Present Limits:

• “World’s best” cryogenic radiometry is U = 0.01%

• Primary standards (cryogenic radiometers) operate over limited range and relatively “high” powers • Typical operation is ~100 uW to ~1 mW • Dissemination to customers degrades due to transfer standard limits ~1% • Optical power traceability has the poorest uncertainty of major measurands

• Difficult to link the lower range of optical powers to primary standards

No formal connection between classical methods to measure optical power and new methods to measure single photons

Bridging the Gap The gap

15 order-of-magnitude gap between cryogenic radiometry and single photon metrology

Cryogenic Radiometer -4 minimum (LOCR) -6 -8 -10 -12 Highest efficiency -14 Attempt to close the gap by single-photon detector comparing calibrations done @ 10 kHz count rate -16

Log (opticalpower)Log classically and with a heralded For λ = 1 µm photons -18 photon source (2007) -19 1 photon/s E=2x10 J -20 No traceability between conventional radiometry and photon counting Bridging the Gap Opportunity: Single Photon Tools for the Gap

Light arrives in packets (quanta – photon)

Optical Power = Energyphoton × rate = h ×n × rate Relies only on Planck’s constant, measurement of wavelength, and accurate measurement of rate

Independent of existing radiometry Opportunity: Single Photon Tools for the Gap

Light arrives in packets (quanta – photon)

Optical Power = Energyphoton × rate = h ×n × rate Source: that emits a known number of photons Detector: that counts a known number of photons

Independent of existing radiometry standards & Inherently single photon Caution!

This talk:

• What this talk is about: – “Bridging the gap” between cryogenic radiometry & photon counting

• What this talk is not about: – “Quantum Candela” Bridging-the-Gap efforts

Manoocheri talk: Wed Bridging the Gap Few-Photon Metrology (many talks) at NEWRAD & Single Photon Workshop 2011

• Brida: Toward Traceable Few Photon Radiometry (NEWRAD) • Arp: Calibration Of Photomultiplier Tubes For Few Photon Applications Using Synchrotron Radiation (NEWRAD) • Gerrits: Extending Single-Photon Optimized Superconducting Transition Edge Sensors Beyond the Single-Photon Counting Regime (NEWRAD & SPW) • Smith: Quantum-enhanced metrology in the real world: Losses, decoherence, and noise make life on the quantum edge challenging (SPW) • Müller: Towards Traceable Calibration of Single Photon Detectors Using Synchrotron Radiation (NEWRAD & SPW) • Rastello: Metrology Towards Quantum-Based Photon Standards (SPW) • Porrovecchio: A transfer standard for the low power / few photon regime – the trap detector plus switched integrator amplifier (NEWRAD & SPW) • Schmunk: Relative detection efficiency calibration of single photon avalanche photo detectors using non-classical light (SPW) • Lehman: Fiber-Coupled Cryogenic Radiometer with Carbon Nanotube Absorber (NEWRAD) • Götzinger, Single-photon sources with near unity efficiency (NEWRAD) • Kück, Towards novel AlN and GaN based single photon sources (NEWRAD) New Bridging-the-Gap efforts

Traceability for single-photon sources The development of highly efficient quantum light sources at the single photon level and the development of entanglement assisted measurement techniques would enable classical measurement limits to be overcome. These new traceable photon sources will underpin the growth of several emerging technologies, such as optical devices for quantum communication, computing, microscopy, nanosciences, nanofabrication and other new production technologies, as well as fundamental metrology.

EMRP Call 2011 - Health, SI Broader Scope & New Technologies Objectives: Traceability for single-photon sources

The JRP shall focus on the traceable measurement and characterisation of source-based standards for photon metrology spanning the range 1 photon/s to 108 photons/s.

The specific objectives are:

1. To develop absolute and calculable single photon sources with high dynamic range at both telecom and visible wavelengths. 2. To develop efficient single-photon sources, to support for SI traceable photon radiometry. 3. To develop quantum optical state sources for entanglement enhanced measurements. 4. To develop optimised photon-coupling strategies and methods between source and detector.

The sources developed in objectives 1-3, should be characterised for photon flux, and by appropriate metrics in terms of statistics, anti-bunching, indistinguishability, degree of entanglement and sub-shot-noise as required by the application. EMRP Call 2011 - Health, SI Broader Scope & New Technologies Why is there cause for hope?

15 order-of-magnitude gap between cryogenic radiometry and single-photon metrology

Cryogenic Radiometer -4 minimum (LOCR) -6 -8 -10 -12 Highest efficiency single -14 Attempt to close the gap by photon detector @ 10 kHz comparing calibrations done count rate -16 Log (opticalpower)Log classically and with a heralded For λ = 1 µm photons -18 photon source (2007) -19 1 photon/s E=2x10 J -20 No traceability between conventional radiometry and photon counting Bridging the Gap Single-Photon Sources

RSI 82, 071101(2011) Atomic Cascade coincidence & PDC(kwiat) vs year.qpc 107

106

105

104 Progress of Single-Photon Sources 3 10

102

1 (limited by detector saturation) Coinc/sec 10 100

Embedded plot in document PQE2009cshorter with Atom&PDC 10-1 1960 1970 1980 1990 2000 year 107 6 10 PDC FWM 105 4 10 Atomic Cascade Kwiat 103 102 101 Cf. PDC 106/s 100 detected pair rate (/s) rate pair detected 4-fold coinc 10-1 1960 1970 1980 year 1990 2000 2010 Single-Photon Detectors Effici Max ency Count h >50% rate

>100 MHz Radiometric Standards including single-photon tools

Sources Detectors Blackbody Trap: Radiometer

T Electrical Substitution Temperature Radiance Radiant power

Synchrotron e- Trap: B-field Semiconductor

Radiant power B-field, current, energy Radiance Radiance: Heralded Source single photons

w1 w1

w 0 w 0 PA R A M E T R I C CR Y S T A L w2 PA R A M E T R I C CR Y S T A L w2 Bridging the Gap: from both ends

• Reaching downwards to photon counting levels • Cryogenic radiometers Cryo -4 • Transfers from Cryogenic radiometers -6 • Source standards -8

-10 • Reaching upwards to cryogenic radiometry levels -12 • Single photon sources- -14 104

countable single photon generation rates -16 Log (opticalpower)Log -18 • Single photon detectors- 1 photon/s -20 countable single photon detection rates

Bridging the Gap Extending Source Dynamic Range Downward

Synchrotron linearity through high dynamic range e- beam current

11-Decade Dynamic Range achieved Radiant intensity uncertainty 0.03%* *Not including: Window transmittance, bandwidth Irradiance uncertainty 0.36% Appl. Opt. 46 25(2007)

Source linearity through high dynamic range Optical Density

OD=10 transmittance uncertainty=few % Extending Detector Dynamic Range Downward

Si photodiode & amplifier Noise= 800 photons/sec with 400 s measurement times

Appl. Opt. 30 3091(1991)

1 2 Spectrum Detector 1003 2008 gain10 Det#1-10 3 4 5 5 10-5 6 7 8 9 3 10-5 10 equivalent  (V) photon noise

10-5 10-5 V @ gain 10 = 1 fA =8950 photons/s 9000 photon/s 8 10-6

6 10-6

4 10-6

-6 2 10-6 2x10 V @ gain 10 = 0.2 fA= 1790 photons/sec 1800 photon/s 10 100 Measurement Time (sec) Extending Cryogenic Radiometer Dynamic Range Downward • Typical Cryo Radiometer- – max power 1 mW – Noise 3 nW – Absolute accuracy 0.005% • NIST pW-ACR (Carter et al. Metrologia 2009) – Temp sensor: noncontact TES magnetization – Max power 20 nW – Noise 1 fW – Absolute accuracy 0.1% • Fiber radiometer – < 1 nW noise – Flat absorber – Carbon nanotube (Lehman Tues. talk) Conventional radiometer pW-radiometer

heatsink (substrate)

membrane

shutter radiant flux absorber

receiver

thermometer heater thermallink heat sink thermal link

W-TES MoCu TES Conventional radiometers

10-15 10-12 10-9 10-6

Optical power [W] Tomlin talk: earlier today Fully Lithographic Fiber-coupled Cryogenic Radiometer for Picowatt Powers 0.1- 70 pW

heater TES wiring thermometer

absorber

0.43 mm Tomlin talk: earlier today Throwing Single Photon Tools at the Gap

Atomic Cascade coincidence & PDC(kwiat) vs year.qpc 107

106

105

104 Single Photon Sources Advancing 3 10

102

1 (limited by detector saturation) Coinc/sec 10 100

Return to a “standard candle” – Single-photon devices that provide Single-photons on demand • Dial in the rate • Dial in the wavelength • “Known optical powers” on demand to calibrate devices

Turn present radiometry measurements into high accuracy counting measurements.

Change the way optical power is disseminated!!

Bridging the Gap Quantum Dot single photon sources

Current limitations: Goals: emission rate (80 MHz) 3 GHz emission efficiency (0.1%) 99% Single QD in micropillar

First direct meas. of homogeneous linewidth; 400 emission rate up to 10 GHz theoretically possible) g(2)(0) ≈ 0.04

New Ideas

“inverse” QD single photon detector Coincidences (optical pump, electrical trigger) 0 -75 -50 -25 0 25 50 75 Time Delay (ns) 3D microcavity: vertical oxide/semiconductor DBRs and transverse circular air/semiconductor DBRs

Ultimate outcome: Countable photons-from-a-box for self-service traceability

Bridging the Gap Single Photon Detectors Transition Edge Sensor (TES) Microbolometer

Optimized for l = 1550 & 810 nm, DE 98+% R Rn Energy Thermometer deposition

-20 T Energy Resolution = 2x10 J !

Absorber, C Counts

Weak thermal link, g

Thermal sink (50 mK)

Photon # It Can Really Count Photons

• Optimized now for photon-number resolution, not

speed (trise~100 ns, tfall~few ms) • Absorption events show good distinguishability • Much slower than APDs S. Nam Transition Edge Sensors – Photon Number resolving

Current performance: Detection efficiency >95% U = ?? at 1550nm recovery times approaching 1ms Strategy to reach goals: Optical packaging Coating design Material science for compability of coatings with superconductors Fast electronics Possibility: Recovery times < 1ms Detection efficiency >99% Plus ……

Thomlin -Gerrits: Thurs. presentation Bridging the Gap Smart TES signal processing

No inherent deadtime:

Deadtime-free processing: Simple, cheap, high throughput signal processor

physics.nist.gov/Divisions/Div844/ FPGA/fpga.html

Deadtime of the monitoring circuits could prevent a correct interpretation of the waveforms, especially in (c). Transition Edge Sensor: Pushing the Limits

Thomas Gerrits Talk by Tomlin Rn later today R

few photons 50,000 photons

TES TES Response TES TES Response

time (ms) time (ms)

I ~1ms Amplitude vs. Width I ~500ms t t Superconducting Nanowire Single-Photon Detector (SNSPD)

Current performance: Detection efficiency ~1% at 1550nm recovery times ~20ns Strategy to reach goals: Make Detectors at NIST Optical packaging and coating design Coating design Material science for compability of coatings with superconductors Fast electronics 10 mm Outcomes: Detection efficiency >75% Extremely challenging nanofabrication and High count rates (>100 MHz) material science problem

Bridging the Gap Quantum Dot Single-Photon Detector (QDOGFET)

hn Current limitations: Goals: Source detection rate: 400 kHz* 1 MHz – 10 MHz 3 4 5 counting: 10 photons 10 -10 photons 5 mm Drain 4 g 6 bunch 10 10 X 10 = 10 Hz Gate bunch s

*B. E. Kardynal, et al., Appl. Phys. Lett. 84, 419 (2004). Single photon traceability: N = 0 N=1.1 Idea: 1

Use the QDOGFET’s number sensitive ability 5 10 2

Counts 3 4 (over a large dynamic range) to count bunches 10

3 of photons. This way you don’t have to count 10 Response 2

so fast! 10 Signal 1 10 0 Challenges: 10 -1 Speed/noise: use on-chip cryogenic amplification 10 -1 0 1 2 3 4 5 Overall detection efficiency: integrated resonant 10 10 10 10 10 10 10 cavity design, solid emersion lens coupling, Number of Photons transparent gate 103 105 Understand the dynamic range with great precision Dynamic Range

Bridging the Gap

Bridge Plan: Overlap power ranges

Today Ultimate Goal gap: 1015 0 best uncertainty: 0.01 % (k=2) 0.001% (k=2) LOCR minimum State of the art - level -4 Classical Next gen -6 (laser, blackbody) LOCR -8 -10 TES bolometers -12 QDOGFET -14 high flux QD-SP source SNSPD TES detector -16 heralded @ 3 GHz (100 MHz) (1 MHz) 1 photon/s -18 photons

-20 (W)) power (opticalLog

Detectors Sources

Bridging the Gap Promise and Concern

• Single Photon radiometry: holds promise of moving radiometry to counting problem

• Efficiencies remain an issue Common Issue: Efficiency

Trap: T

Collection efficiency

99.6(1)% 99.997(3)% Extraction efficiency w1

T w 0 PA R A M E T R I C CR Y S T A L w2

80.83(13)% Single Photon Examples of Efficiency Issues

Götzinger: Wed Single-photon sources with near unity efficiency Bridging the Gap FWM Fiber Source Brightness

ProgressChannel detection effic vs year.qpc fiber source matrix.xls 105

104

103 detected pairrate (/s) 102 4-fold coinc 2002 2003 2004 2005 2006 2007 2008 year Fiber Source Efficiency Progress Two-Photon Detector Efficiency Scheme No External Standards Needed!

Detector to be Calibrated A bs o l u t e w C OU NT E R Detection 1 E f f ic i e n c y

C OI NC N C OU NT E R w 0

P AR A M E TR IC C RY S TA L w 2 C OU NT E R Trigger or “Herald” Detector

N1=h1N N2=h2N NC=h1h2N

h1=NC/ N2 Verifying the Method

A bs o l u t e Calibrated Detection E f f ic i e n c y Si Detector Comparison

Absolute C OU NT E R Detection E f f ic i e n c y DUT C OI NC N C OU NT E R w 0

P AR A M E TR IC C RY S TA L w 2 C OU NT E R Trigger Two-Photon-Based SPD Detection Efficiency Calibration

Sources of uncertainty:

DUT Collection Efficiencies absorpt ion Spatial Coinc. Angular Trigger

DUT Spectral reflect ion

… Coinc.

Trigger

geomet ric DUT

Coinc.

Trigger Trigger counting Coincidence determination Correlated photon calibration method uncertainty budget Relative Relative uncertainty uncertainty of value of DE Physical property Value (%) Sensitivity (%) Crystal reflectance 0.09249 0.2% 0.1 0.02%

Crystal transmittance 0.99996 0.009% 1 0.009% Optical losses Lens transmittance 0.97544 0.0027% 1 0.0027% Geometric collection (raster scan) 0.9995 0.05% 1 0.05%

DUT filter transmittance 0.9136 0.1% 1 0.10%

Trigger bandpass to virtual bandpass/wavelength 0.07%

Histogram background subtraction 0.03% Histogram Coincidence circuit correction 0.0083 10.0% 0.008 0.084% Counting statistics 0.08% Deadtime (due to rate changes with time) 0.02%

Trigger afterpulsing 0.0025 25.0% 0.003 0.06% Trigger Trigger background, & statistics 175000 0.3% 0.035 0.01%

Trigger signal due to uncorrelated photons 0 0.07% 1 0.07% Trigger signal due to fiber back reflection 0.00202 1.60% 0.002 0.003% Total 0.18% Detector substitution calibration uncertainty budget

Relative Relative uncertainty uncertainty of value of DE Physical property Value (%) Sensitivity (%) Analog transfer standard calibration (QE equivalent) 0.61906 0.10% 1 0.10% Spatial nonuniformity at 700nm, (standard deviation of central responsivity) 1 0.025% 1 0.025%

Analog measurement statistics & drift 0.06% Analog amplifier gain calibration 1.0022 0.050% 1 0.05% Pinhole backside reflection 0 0.1% 1 0.10%

DUT signal & background statistics 0.003% DUT afterpulsing 0.00322 11.6% 0.003 0.04%

DUT deadtime (due to rate changes with time) 0.02%

Total Uncertainty 0.17% Summary of Single-Photon Promise and Concerns

• Single Photon radiometry: holds promise of moving radiometry to counting problem

• Efficiencies remain an issue

• Building bridges is good

• Burning a Candela requires caution