Measuring the local response of a nanowire SSPD

Qiang Wangwang@physics.leidenuniv.nl

Leiden UniversityThe Netherlands

J. J. Renema

M. J. A. de Dood

R. GaudioA. FioreM. P. van Exter

A. Engel

16th LTDGrenoble July 2015

Nano Lett., 2015, 15, 4541

Introduction

Superconducting single photon detector (SSPD)

(Fabricated in TU/e)

Applications: Space-Ground communication Photon number resolving detector Quantum Key Distribution (QKD)

90% detection efficiency < 1 dark / min 20 ps jitter wavelength up to 5 µm

1μm

V. Anant et.al., Opt. Exp., 16, 10750 (2008)

TM TEwire

pitch

R = η · IDE η : optical absorption, AbsTE,TM(x),

ηTE > ηTM IDE : internal detection efficiency, IDETE > IDETM ?

η TE,TM = ∫ AbsTE,TM (x)dx𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤

ηTE > ηTM

Introduction

Measurement:Detection probability R with varying polarizations (TE & TM).

Single nanowire SSPD

No bends No current crowdingLess defect High critical current

J. J. Renema, Q. Wang et.al., Nano Lett., 15, 4541(2015)

QDT results1 Complete characterization of the single wire SSPD2 Separation of η and IDE, IDE= p1

Quantum Detector Tomography (QDT)

J. J. Renema et al., Opt. Express, 20, 2806 (2012)

Characterization on SSPD

𝑅𝑅 𝑁𝑁 = 𝑒𝑒−η𝑁𝑁 𝑝𝑝1η 𝑁𝑁 + 𝑒𝑒−η𝑁𝑁�𝑤𝑤=2

∞

𝑝𝑝𝑤𝑤(η𝑁𝑁)𝑤𝑤

𝑖𝑖!N: mean photon number ∝ input laser power

η : polarization dependent, AbsTE,TM (x) IDE : polarization dependent,

Experimental results (λ=1500nm)

J. J. Renema, Q. Wang et.al., Nano Lett., 15, 4541(2015)

η : polarization dependent, AbsTE,TM (x) IDE : polarization dependent, position-dependent,

Experimental results (λ=1500nm)

Assumption:IDETE,TM = ∫ LDE(x) * AbsTE,TM (x)dx / Absorption Local Detection Efficiency LDE(x), Full description of SSPD

J. J. Renema, Q. Wang et.al., Nano Lett., 15, 4541(2015)

Local Detection Efficiency

Visibility (λ)= (IDETE - IDETM)/(IDETE + IDETM)

Fitting parameters,To be determined

IDETE,TM = ∫ AbsTE,TM (x) ∗ LDE (x) dxAbsorption

Measurement (λ),Tomography

FDTD simulation

LDE (x) ?

J. J. Renema, Q. Wang et.al., Nano Lett., 15, 4541(2015)

Local Detection Efficiency

Visibility (λ)= (IDETE - IDETM)/(IDETE + IDETM)

Fitting parameters,To be determined

IDETE,TM = ∫ AbsTE,TM (x) ∗ LDE (x) dxAbsorption

Measurement (λ),Tomography

FDTD simulation

LDE (x) ?

J. J. Renema, Q. Wang et.al., Nano Lett., 15, 4541(2015)

Position dependent LDE(x) [1] Highly efficient edge at low bias currents Photon-assisted vortex-entry model [2]

Local Detection Efficiency(λ=1500nm)

1 J. J. Renema, Q. Wang et.al., Nano Lett., 15, 4541(2015)2 A. Engel et al., IEEE Trans. Appl. Supercon., 25, 2200407, (2015)

(Mirror Symmetry)

Response of meandering structures

Response of meandering structures

Response of meandering structures

Quantitative agreement between theory and experiment!

• Detection event: Position dependent, LDE(x)• Wire Edges are more sensitive than center• Quantitative agreement with meander SSPDs

Conclusions

J. J. Renema et al., Opt. Express, 20, 2806 (2012)J. J. Renema, Q. Wang et.al., Nano Lett., 15, 4541(2015)

Thanks!

Local Detection Efficiency

J. J. Renema, Q. Wang et.al., Nano Lett., 15, 4541(2015)A. Engel et al., IEEE Trans. Appl. Supercon., 25, 2200407, (2015)

Photon-assisted vortex entry model electron excited by photon breaking Cooper pairs leads to quasiparticles Redistribution of superconducting e- or Ib Edge-barrier for vortex-entry is lowered Energy dissipation by moving vortex leads to normal state

Results: Theory and ExperimentLDE(x,Ib) = min{1, exp(Ib-Ith(x))/I*}

Threshold current Ith(x), based on Vortex entry model. [1]

Ith(x, λ)=Ic -ϒ(x) hcλ

Comparison of calculation (dashed) and experiment (solid), wavelength = 1500 nm. [2]

1 A. Engel et al., IEEE Trans. Appl. Supercon., 25, 2200407, (2015)2 J. J. Renema, Q. Wang et.al., arXiv:1504.05003)

Local Detection Efficiency

A. Engel, et. al., J. Mod. Optics 56, 352 (2009) A. Engel, et. al., IEEE Trans. Appl. Supercon., 25, 2200407, (2015)

Theory: photon-assisted vortex entry modelelectron excited by photon

breaking Cooper pairs leads to quasiparticlesRedistribution of superconducting e- or IbEdge-barrier for vortex-entry is lowered

Energy dissipation by moving vortex leads to normal state

Local Detection Efficiency

• Vortex barrier = (Self-Energy) + (Interaction I)

G(x,I)=ln[2wπξ

cos πxw ]ε + −𝐼𝐼

𝐼𝐼𝑐𝑐

2(x+w/2)exp 1 𝜉𝜉

εε ∝ ns , density of superconducting electrons

• Position dependentPhoton absorbed on the edgens , I , (Interaction I) ;ns , ε , G(x,I) .

• Consequence: barrier lowered, vortex enters easier.• Detection event: Position dependent

Local Detection Efficiency

Experimental data Fitting parameters

Fit to the model

Ib (μA)

Quantum Detector Tomography

J. J. Renema et al., Opt. Express, 20, 2806 (2012)

Tomography results: Separation of linear absorption and nonlinear

internal detection efficiency Completely characterization of SSPD with low efficiency

𝑅𝑅 = 𝑒𝑒−η𝑁𝑁�𝑤𝑤

𝑝𝑝𝑤𝑤(η𝑁𝑁)𝑤𝑤

𝑖𝑖!

pi