Generation of ultra-broadband entangled photons from chirped-MgSLT crystal: towards mono-cycle temporal

entanglement generation

Akira Tanaka*a,b, Ryo Okamoto a,b, Hwan Hong Lim c, Shanthi Subashchandrana,b,

Masayuki Okanoa,b, Labao Zhangd, Lin Kangd, Jian Chend, Peiheng Wud,

Toru Hirohatae, Sunao Kurimurac and Shigeki Takeuchia,b

takeuchi@es.hokudai.ac.jpa. Research Institute for Electronic Science, Hokkaido University, Japanb. The Institute of Scientific and Industrial Research, Osaka University, Japan c. National Institute for Materials Science, Japand. Research Institute of Superconductor Electronics, Nanjing University, Chinae. Central Research Laboratory, Hamamatsu Photonics, Japan

Univ. of Virginia Charlottesville, USA 2013.2.11

About me• B.S. @ Osaka Univ. (2005.4-2009.3, Prof. N. Imoto’s LAB.)

Thesis: theory on efficient classical simulation of Q.C.

• M.S. @Osaka Univ. (2009.4-2011.3, Prof. S. Takeuchi’s LAB.)

Q-state tomography of tapered fiber-microsphere cavity system

Opt. Express 19 (3), 2278--2285 (2011)Ex. on Parametric Down Conversion and quantum interference

(Prof. S. Takeuchi’s Lab.)

• D.C. @ Osaka Univ. (2011.4- Now, Prof. S. Takeuchi’s LAB.)

Ex. on ultra-broad PDC using chirped-QPM crystal and its temporal

compression

Opt. Express 20 (23), 25228--25238 (2011)

Our institutes

Osaka Univ.

We work here

Hokkaido Univ.

Our lab belongs

to here

Quantum gates (simplified CNOT, Entanglement filter, KLM-CNOT) & Quantum metrological applications (NOON states)

diameter: 178µmTaper Nano Fiber

Microsphere cavity (Ｑ～107)

Diamond Nitrogen Vacancy center

Diffraction-limitedLight confinement

Low Temp. (4K)exciting ZPL of NV

1. Quantum Information Processing using Photons.

Our activities

2. Manipulating Light Quanta using Nano Technology.

OkamotoFujiwaraOkano

Tanida

Tanaka

Zhao

Takeuchi

Kasagi

Shanthi

Sagawa

Yokoi

Members of Quantum & Advanced optics group 2012,

RIES, Hokkaido Univ. & ISIR Osaka Univ. (temporally in

Osaka now)

Kamioka

Oyama

ItoOnoYoshida

Eto

Collaborators on this work

Prof. Sunao Kurimura, NIMS

Dr. Hwan-Hong Lim, NIMS

Prof. Peiheng Wu, Nanjing Univ.

Prof. Jian Chen, Nanjing Univ.

Dr. Toru Hirohata, Hamamatsu Photonics. K.K.

3. Metrological application using Monocycle Entangled Photons

• Monocycle entangled photon source

• Two-photon temporal compression

• Chirped-MgSLT crystals

• Collinear SPDC experiment

• Non-collinear SPDC with two broadband detectors

• Estimates on two-photon temporal widths

• Next step: measuring frequency correlation

• Conclusion

Outline

Monocycle entangled photon source (MEPS)A state where two photons are correlated in a very short time (a

few femtoseconds), only one cycle of light oscillation.

Quantum Optical Coherence

Tomography

Efficient Two-Photon Absorption

Clock Synchronization

(Theory)

M.B. Nasr et al., PRL91, 083601 (2003)

B. Dayan et al., PRL93, 023005(2004)

V. Giovannetti et al., PRL87, 117902(2001)

< µm resolution MHz resolution fs precision

Possible Applications to Quantum MetrologyPossible Applications to Quantum Metrology

Classical Monocycle Pulses Monocycle Entangled Photons

t

few fs few fs

tConstant

Low prob.

Broad (~200THz)

Random

High prob.

Narrow (~MHz or smaller)

Timing

Pair production

Energy sum

S.E. Harris, PRL 98, 063602 (2007).

Requirements for monocycle entanglement

ts

ti

Ultra-broad

(octave span)

Ultra-short

(~several fs)

Frequency

domain

Time

domain

Wave-function of monocycle-entangled photons

νs

νi

∆ν

Frequency correlation

∆t

Temporal correlation

Large ∆ν is required to achieve monocycle entanglement.

Nonlinear optical crystal

CW-laser

Worse pair production∝∝∝∝L2

Thin crystal length L

Increase ∆ν

Method: Parametric down conversion Problem.

Current status towards realizing MEPS2007 Theoretical proposal S.E. Harris, PRL 98, 063602 (2007).

2008 Non-collinear, ∆λ = 400 nm, 404 nm pumpM.B. Nasr et al., PRL 100, 183601 (2008).

2009 Collinear, ∆λ = 700 nm, 532 nm pumpN. Mohan et al., Appl. Opt. 48 (20) 4009 (2009).

2010 Preliminary chirp & compress with ∆λ = 40 nm, 532 nm pumpS. Sensarn et al., PRL 104, 253602 (2010).

2012 (This talk) Non-collinear, ∆λ = 820nm, 532 nm pump

Akira Tanaka et al., Opt. Express 20 (23), 25228 (2012).

420nm420nm

Frequency separator

Nonlinear optical crystal

Chirped Quasi-phase-matched (QPM) deviceChirped Quasi-phase-matched (QPM) device

Idler: 1.0～4.5µm

Signal: 0.46～0.75µm

MEPSMEPScontrol

Dispersion

control

3.11µm 7.02µmPolingperiods

0.75&1µm 0.46&4.5µmGenerated

photonsContinuous tuning of ωs&ωi

Two-photon temporal compression

Efficient method for two-photon compression

Less chirp & less bandwidth to achieve the same temporal width

Dispersion

control

Dispersion

control

S. E. Harris, PRL 98, 063602 (2007).

Previous scheme

Dispersion

control

Dispersion

control

Our scheme

A. Tanaka et al, Opt. Exp. 20, 25228 (2012)

Chirped-

QPM

Chirped-

QPM

Frequency domain

200THz

375THz

Time domain

4.4fs

4.4fs

Chirped-MgSLT crystals

8.000 µm 8.128 µm

8.000 µm 8.256 µm

8.000 µm 8.550 µm

8.000 µm 8.825 µm

Fabricated chirped-QPM gratings

no chirpCalc.

Fabrication: chirped-MgSLT crystals of different chirp rates

(1.0 mol %) Mg-doped Stoichiometric Lithium Tantalate (MgSLT)

A. Tanaka et al, Opt. Exp. 20, 25228 (2012) (10%-chirped crystal only)

Fabricated by H.H. Lim& S. Kurimura (NIMS)

Pump photons

Pertier unit 0.5mm

0.5mm

20mm

DimensionPicture

• Type-0 (e+e→e) PDC process

• Flat parametric gain due to linear chirp

Maximal bandwidth of 200THz

with 10%(8.0-8.8µm) chirped device

Previous SPDC experiments

Wavelength ranges of two photons agreed with theory*After calibration of detector Q.E.

Problems

• Complex measurements due to limited detector wavelength range

• Broadband single photon detectors are needed for QOCT application

Meas.Meas. Meas.Meas.

Si-CCDSi-CCD InGaAs-PDAInGaAs-PDA

Calc.Calc.

Meas.Meas.

Calc.Calc.

Meas.Meas.

chirp

small

chirp

largechirp

large

chirp

small

5×10-6

1×10-8

1×10-7

1×10-6

5×10-8

5×10-7

5×10-6

1×10-8

1×10-7

1×10-6

5×10-8

5×10-7

New SPDC experiment

SNSPD

PMT

+RF Amps.

8 µm 8.825 µm

Setup

Single-photon spectra are measured both by SNSPD and PMT

Photo-Multiplier Tube

InP/InGaAs photocathode

Broadband detection (<0.4-1.6 µm)

Flat Q.E. for 500-1600nm

New device from Hamamatsu Photonics

M. Niigaki, T. Hirohata et al, APL 71, 2493 (1997).

Superconducting Nanowire Single Photon Detector

NbN nanowire (bias current: 37 µA)

Broadband detection (<0.6-2.0 µm)

Q.E. exponential decays for λ

Collaboration with Nanjing Univ.

S. Subashchandran et al, Proc. SPIE 8268, 82681V-2 (2011).

Cryo-cooler(3.7K)

A. Tanaka et al, Opt. Exp. 20, 25228 (2012)

±0.25deg.

532nm, 2W

New SPDC experiment: results

Non-collinear photons span 194THz (1.2cycle)

SNSPD PMT

Calc.

Calc.

*Calibrated (a) detector Q.E. and (b) filter transmittances

8 µm 8.825 µm

A. Tanaka et al, Opt. Exp. 20, 25228 (2012)

194THz

185THz

(due to Q.E. of PMT)

Signal

Idler

Signal

Idler

Two-photon temporal widths

Calculated temporal correlation

with different chirps

11.8 fs

10.0 fs

7.1 fs

4.4 fs

3.3 cycle

2.8 cycle

2.0 cycle

1.2 cycle

A. Tanaka et al, Opt. Exp. 20, 25228 (2012) (max-chirped crystal only)

chirp small large

Our chirped-MgSLT can herald 1.2-cycle two-photons

Next step: measuring frequency correlation

Experimentally tested to verify broadband frequency correlation

Preliminary frequency correlation measurement

ν1

ν2

APDAPD

ν2

ν1

PMTPMT

coincicoincidence

Coincidence countsChirped

-MgSLT

Previous measurement

Chirped

-MgSLT

• Single photon spectra

are measured

Chirped

-MgSLTcorrelated?

Question• For QOCT application

detection of correlated

modes is necessary

Preliminary results of frequency correlation

Single-photon spectrum

Joint spectrum

940-1200 nm

Bandwidth: 65 THz

Coincidence degradation

1) Q.E. of detectors

2) Low throughput at large filter tilt

Observed two-photon frequency correlation (65THz)

65THz

8 µm 8.128 µm

With 1.6% chirped device

1. Non-collinear SPDC enables an efficient two-photon compression

2. Measured collinear two-photons from four chirped-MgSLT crystals agreed with theoretical spectral width

3. Octave-spanning (820nm, 200THz) non-collinear two-photons are observed using Superconducting Nanowire SPD and PMT

4. Fabricated 10%-chirped device can herald 1.2 cycle correlation

5. Two-photons emitted from 1.6%-chirped QPM grating have frequency correlation width larger than 65 THz

AcknowledgementWe thank Prof. Mikio Yamashita for kind discussion and Mr. Takahiro Shimizu for instruction in devicefabrication. This work is supported by JST-CREST, Quantum Cybernetics, JSPS-FIRST, the JapaneseSociety for the Promotion of Science, the Research Foundation for Opto-Science and Technology,Special Coordination Funds for Promoting Science and Technology, a Grant-in-Aid for JSPS Fellows(11J00744), JSPS Research Fellowships for Young Scientists and the G-COE program.