Univ. of Virginia Charlottesville, USA 2013.2.11 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 Subashchandran a,b , Masayuki Okano a,b , Labao Zhang d , Lin Kang d , Jian Chen d , Peiheng Wu d , Toru Hirohata e , Sunao Kurimura c and Shigeki Takeuchi a,b takeuchi@es.hokudai.ac.jp a. Research Institute for Electronic Science, Hokkaido University, Japan b. The Institute of Scientific and Industrial Research, Osaka University, Japan c. National Institute for Materials Science, Japan d. Research Institute of Superconductor Electronics, Nanjing University, China e. Central Research Laboratory, Hamamatsu Photonics, Japan
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. Hokkaido Univ. We work here Our lab belongs to here
Our activities 1. Quantum Information Processing using Photons. Quantum gates (simplified CNOT, Entanglement filter, KLM-CNOT) & Quantum metrological applications (NOON states) 2. Manipulating Light Quanta using Nano Technology. diameter: 178 µ m Taper Nano Fiber Diffraction-limited Microsphere Low Temp. (4K) Diamond Nitrogen cavity ( Ｑ～ 10 7 ) Light confinement exciting ZPL of NV Vacancy center
3. Metrological application using Monocycle Entangled Photons Members of Quantum & Advanced optics group 2012, RIES, Hokkaido Univ. & ISIR Osaka Univ. (temporally in Osaka now) Tanida Yokoi Oyama Takeuchi Okamoto Fujiwara Eto Okano Tanaka Shanthi Zhao Ono Ito Kamioka Sagawa Kasagi Yoshida 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.
Outline • 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
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. Classical Monocycle Pulses Monocycle Entangled Photons few fs few fs t t Constant Random Timing S.E. Harris, PRL 98 , 063602 (2007). Pair production Low prob. High prob. Energy sum Broad (~200THz) Narrow (~MHz or smaller) Possible Applications to Quantum Metrology Possible Applications to Quantum Metrology Quantum Optical Clock Efficient Two-Photon Coherence Synchronization Absorption Tomography (Theory) < µm resolution MHz resolution fs precision V. Giovannetti et al., B. Dayan et al., M.B. Nasr et al., PRL 87 , 117902(2001) PRL 93 , 023005(2004) PRL 91 , 083601 (2003)
Requirements for monocycle entanglement Wave-function of monocycle-entangled photons Frequency Frequency correlation Ultra-broad ν i ∆ν domain (octave span) ν s Ultra-short Temporal correlation Time t i (~several fs) domain ∆ t t s Large ∆ν is required to achieve monocycle entanglement . Method: Parametric down conversion Problem. Increase ∆ν CW-laser Thin crystal length L Worse pair production ∝ ∝ ∝ ∝ L 2 Nonlinear optical crystal
Current status towards realizing MEPS 2007 Theoretical proposal S.E. Harris, PRL 98 , 063602 (2007). Chirped Quasi-phase-matched (QPM) device Chirped Quasi-phase-matched (QPM) device Poling Frequency separator 3.11µm 7.02µm periods Signal: 0.46 ～ 0.75µm 420nm 420nm Dispersion control control MEPS MEPS Generated 0.75&1µm 0.46&4.5µm Nonlinear optical crystal photons Continuous tuning of ω s &ω i Idler: 1.0 ～ 4.5µm 2008 Non-collinear, ∆λ = 400 nm, 404 nm pump M.B. Nasr et al. , PRL 100 , 183601 (2008). 2009 Collinear, ∆λ = 700 nm, 532 nm pump N. Mohan et al ., Appl. Opt. 48 (20) 4009 (2009). 2010 Preliminary chirp & compress with ∆λ = 40 nm, 532 nm pump S. 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).
Two-photon temporal compression Efficient method for two-photon compression Previous scheme Frequency domain Time domain Dispersion Dispersion Chirped- control control QPM 4.4fs 375THz S. E. Harris, PRL 98 , 063602 (2007). Our scheme Dispersion Dispersion Chirped- control control QPM 200THz 4.4fs A. Tanaka et al, Opt. Exp. 20, 25228 (2012) Less chirp & less bandwidth to achieve the same temporal width
Chirped-MgSLT crystals A. Tanaka et al, Opt. Exp. 20, 25228 (2012) (10%-chirped crystal only) Fabrication: chirped-MgSLT crystals of different chirp rates (1.0 mol %) Mg-doped Stoichiometric Lithium Tantalate (MgSLT) Picture Dimension Fabricated chirped-QPM gratings 8.000 µm 8.128 µm Pump photons 0.5mm 8.000 µm 8.256 µm 20mm 8.000 µm 8.550 µm Pertier unit 0.5mm 8.000 µm 8.825 µm • Type-0 (e+e→e) PDC process Calc. no chirp • Flat parametric gain due to linear chirp Maximal bandwidth of 200THz with 10%(8.0-8.8µm) chirped device Fabricated by H.H. Lim& S. Kurimura (NIMS)
Previous SPDC experiments InGaAs-PDA InGaAs-PDA Si-CCD Si-CCD 5 × 10 -6 5 × 10 -6 Calc. Calc. Calc. Calc. 1 × 10 -6 1 × 10 -6 5 × 10 -7 5 × 10 -7 chirp 1 × 10 -7 chirp chirp 1 × 10 -7 chirp 5 × 10 -8 5 × 10 -8 large small small large 1 × 10 -8 1 × 10 -8 Meas. Meas. Meas. Meas. Meas. Meas. Meas. Meas. *After calibration of detector Q.E. Wavelength ranges of two photons agreed with theory Problems • Complex measurements due to limited detector wavelength range • Broadband single photon detectors are needed for QOCT application
New SPDC experiment A. Tanaka et al, Opt. Exp. 20, 25228 (2012) +RF Amps. Setup ± 0.25deg. SNSPD 532nm, 2W PMT 8 µm 8.825 µm Photo-Multiplier Tube Superconducting Nanowire Single Photon Detector S. Subashchandran et al, Proc. SPIE 8268 , 82681V-2 (2011). M. Niigaki, T. Hirohata et al, APL 71 , 2493 (1997). NbN nanowire (bias current: 37 µA) InP/InGaAs photocathode Broadband detection (<0.6-2.0 µm) Broadband detection (<0.4-1.6 µm) Q.E. exponential decays for λ Flat Q.E. for 500-1600nm Collaboration with Nanjing Univ. New device from Hamamatsu Photonics Cryo-cooler (3.7K) Single-photon spectra are measured both by SNSPD and PMT
New SPDC experiment: results A. Tanaka et al, Opt. Exp. 20, 25228 (2012) 8 µm 8.825 µm SNSPD PMT Calc. Signal Idler Signal Calc. Idler 194THz 185THz (due to Q.E. of PMT) *Calibrated (a) detector Q.E. and (b) filter transmittances Non-collinear photons span 194THz (1.2cycle)
Two-photon temporal widths A. Tanaka et al, Opt. Exp. 20, 25228 (2012) (max-chirped crystal only) Calculated temporal correlation with different chirps 11.8 fs 3.3 cycle 10.0 fs 2.8 cycle 7.1 fs 2.0 cycle 4.4 fs 1.2 cycle large chirp small Our chirped-MgSLT can herald 1.2-cycle two-photons
Next step: measuring frequency correlation Previous measurement • Single photon spectra Chirped are measured -MgSLT Question • For QOCT application Chirped detection of correlated correlated? -MgSLT modes is necessary Preliminary frequency correlation measurement APD APD ν 1 Coincidence counts Chirped coinci coinci ν 2 dence -MgSLT PMT PMT ν 2 ν 1 Experimentally tested to verify broadband frequency correlation
Preliminary results of frequency correlation Single-photon spectrum With 1.6% chirped device 8 µm 8.128 µm 65THz 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)
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 Acknowledgement We thank Prof. Mikio Yamashita for kind discussion and Mr. Takahiro Shimizu for instruction in device fabrication. This work is supported by JST-CREST, Quantum Cybernetics, JSPS-FIRST, the Japanese Society 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.
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