QUANTUM OPTICS AND QUANTUM INFORMATION TEACHING LABORATORY at the Institute of Optics, University of Rochester

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Kumar Jha, Laura Elgin, Nickolaos Savidis, Sean White OSA Annual Meeting Special

1 QUANTUM OPTICS AND QUANTUM INFORMATION TEACHING LABORATORY at the Institute of Optics, University of Rochester Svetlana Lukishova, Luke Bissell, Carlos Stroud, Jr, Anand Kumar Jha, Laura Elgin, Nickolaos Savidis, Sean White OSA Annual Meeting Special Symposium Quantum Optics and Quantum Information Teaching Experiments, 12 October 2006, Rochester NY

2 This course introduces both graduate and undergraduate students to the basic concepts and tools of quantum optics and quantum information using modern photon counting instrumentation Photon counting applications bioluminescence single molecule detection medical imaging lighting displays entertainment detector calibration hyper-spectral imaging Biotechnology Electronics primary radiometric scales Metrology photon count quantum standards Quantum Information Processing Medical Physics quantum imaging quantum cryptography quantum computing single photon sources medical / non interactive imaging neutrino/ cherenkov/ dark matter detection Space Applications Meteorology Military radioactivity nuclear IR detectors robust imaging devices remote sensing lidar environmental monitoring night vision security chemical bio agent detection Areas of applications of photon counting instrumentation (prepared by organizers of second international workshop Single Photon: Sources, Detectors, Applications and Measurements Methods (Teddington, UK, October 2005)).

3 New teaching laboratory course consists of four laboratory experiments 1. Lab. 1: Entanglement and Bell inequalities (~ 5 weeks); 2. Lab. 2: Single-photon interference: Young s double slit experiment and Mach-Zehnder interferometer ( ~ 1 week); 3. Lab. 3: Confocal microscope imaging of single-emitter fluorescence (~ 5 weeks); 4. Lab. 4: Hanbury Brown and Twiss setup. Fluorescence antibunching and fluorescence lifetime measurement (~ 1 week).

4 Lab. 1. Entanglement and Bell inequalities In quantum mechanics, particles are called entangled if their state cannot be factored into single-particle states. Entangled A B A B Any measurements performed on first particle would change the state of second particle, no matter how far apart they may be. This is the standard Copenhagen interpretation of quantum measurements which suggests nonlocality of the measuring process. The idea of entanglement was introduced into physics by Einstein-Podolsky-Rosen GEDANKENEXPERIMENT (Phys. Rev., 47, 777 (1935)).

5 In the mid-sixties it was realized that the nonlocality of nature was a testable hypothesis (J. Bell (Physics, 1, 195 (1964)), and subsequent experiments confirmed the quantum predictions. 1966: Bell Inequalities John Bell proposed a mathematical theorem containing certain inequalities. An experimental violation of his inequalities would suggest the quantum theory is correct.

6 Lab. 1. Entanglement and Bell inequalities Creation of Polarization Entangled Photons: Spontaneous Parametric Down Conversion ψ = V V + s i e iφ H s H i

7 Lab. 1. Entanglement and Bell inequalities 1. D. Dehlinger and M.W.Mitchell, Entangled Photon Apparatus for the Undergraduate Laboratory, Am. J. Phys, 70, 898 (2002). 2. D. Dehlinger and M.W.Mitchell, Entangled Photons, Nonlocality, and Bell Inequalities in the Undergraduate Laboratory, Am. J. Phys, 70, 903 (2002).

8 Photograph of experimental setup on entanglement built by the Institute of Optics students To Labview Program

9 Dependence of Co-incidence Counts on Polarization Angle The probability P of coincidence detection for the case of 45 o incident polarization and phase compensated by a quartz plate, depends only on the relative angle β-α: P(α, β) = 1/2cos 2 (β-α) α=0 α=90 Coincidence Counts (for 10 seconds) β ( in degrees)

10 Dependence of Co-incidence Counts on Polarization Angle (continued) Co-incidence Counts (for 10 seconds) α=45 α= β ( in degrees)

11 Aligning the Quartz plate Coincidence Counts versus Quartz Plate Angle Coincidence counts, 5 s N(0,0) N(90,90) N(45,45) Quartz plate angle along horizontal direction (in degrees)

12 Calculation of Bell s Inequality We used Bell s inequality in the form of Clauser, Horne, Shimony and Holt, Phys. Rev. Lett., 23, 880 (1969) Bell s inequalities define the sum S. A violation of Bell s inequalities means that S >2., where: The above calculation of S requires a total of sixteen coincidence measurements (N), at polarization angles α and β: α β α β α β α β

13 Results of Calculation: After collecting data at the appropriate angles, we calculated: S=2.652, a clear violation of Bell s inequalities!

14 Lab. 2. Single-photon interference Concepts addressed: Interference by single photons Which-path measurements Wave-particle duality M.B. Schneider and I.A. LaPuma, Am. J. Phys., 70, 266 (2002).

15 Lab. 2. Single-photon interference Mach-Zehnder interferometer mirror V> NPBSPolarizer D Polarizer A Polarizer C Path 2 screen Path 1 laser Spatial filter PBS Polarizer B H> mirror Polarizer D, absent Polarizer D at 45 No Fringes Fringes

16 Photograph of Mach-Zehnder Interferometer Setup

Polarizer D absent 500000 400000 300000 200000

17 Single-photon Interference Fringes Polarizer D at 45 deg Counts for 10 Seconds Polarizer D absent Position of Detector (mm)

18 Young s Double Slit Experiment with Electron Multiplying CCD ixon Camera of Andor Technologies 0.5 s 1 s 2 s 3 s 4 s 5 s 10 s 20 s

19 Labs 3-4: Single-photon Source Based on Single-emitter Fluorescence Lab. 3. Confocal fluorescence microscopy of single-emitter Sample with single emitters Objective 532 nm/1064 nm, 8 ps, ~100 MHz laser Interference filter Fiber To Hanbury Brown Dichroic Twiss setup mirror Fluorescence PZT stage light Lab. 4. Hanbury Brown and Twiss setup. Fluorescence antibunching and fluorescence lifetime measurements Fluorescent light Start Single photon counting avalanche photodiode modules Stop Nonpolarizing beamsplitter PC data acquisition card

20 Single-photon Source Based on Single-emitter Fluorescence (Labs 3-4) Efficiently produces photons with antibunching characteristics; Key hardware element in Quantum Information technology and quantum cryptography Single photon Alice Bob Eva

21 To produce single photons, a laser beam is tightly focused into a sample area containing a very low concentration of emitters, so that only one emitter becomes excited. It emits only one photon at a time.

Deterministic molecular alignment will provide deterministically polarized photons.

22 We are using liquid crystal as a host Liquid crystal hosts can align the dopant along the direction preferable for excitation efficiency (along the light polarization). Deterministic molecular alignment will provide deterministically polarized photons. k E Chiral liquid crystal hosts with their 1-D photonic band-gap tuned to the chromophore fluorescence band will increase source efficiency and provide circular polarization

23 The main elements of our setup Confocal fluorescence microscope Pulsed 532-nm, 6 ps, 75 MHz rep. rate laser Hanbury Brown and Twiss unit with two avalanche photodiode SPCM Single-photon counting, cooled EM-CCD camera Time-Harp 200 computer card and software to build antibunching histogram APD Start Stop APD LASER EM-CCD CAMERA

24 Schematic of confocal microscope stop laser stop start τ τ t

Samples Emitters: dye molecules or colloidal

concentration (~nm) Hosts: liquid crystals in monomeric

coating on cover-glass slip; - Planar alignment using

25 Samples Emitters: dye molecules or colloidal semiconductor quantum dots of extremely low concentration (~nm) Hosts: liquid crystals in monomeric (fluid) or oligomeric form Fabrication methods: - Spin coating on cover-glass slip; - Planar alignment using either buffing or shifting two substrates relative to each other in one direction

We used two types of emitters with fluorescence max at ~579 nm: (1) single colloidal semiconductor CdSe quantum dots (nanocrystals); (2) DiIC 18 (3) (DiI) dye single molecules Colloidal quantum dots

26 We used two types of emitters with fluorescence max at ~579 nm: (1) single colloidal semiconductor CdSe quantum dots (nanocrystals); (2) DiIC 18 (3) (DiI) dye single molecules Colloidal quantum dots are nanometer sized semiconductor crystals made of ten to thousands of atoms; Behave like giant atoms with size-dependent optical properties; PbSe QDs fluoresce in spectral region of optical communication wavelengths (1.3 and 1.55 μm); Can be used as fluorescence markers in biomedical applications Fluorescence Intensity, QD Fluorescence Spectrum arbitrary units Wavelength, nm Molecular structure of DiIC 18 (3) dye. Absorbing and emitting dipoles are nearly parallel to the bridge (perpendicular to two alkyl chains). Fluorescence intensity, arbitrary units CH CH CH N N Dye Fluorescence Spectrum Wavelength, nm

Definite polarization of emitter fluorescence in planar-aligned liquid crystal hosts Planar-aligned cholesterics with 1-D photonic bandgap structure

light Planar-aligned nematics can provide linearly polarized fluorescence in definite direction for emitters with molecular dipoles Po Reflected RH

27 Definite polarization of emitter fluorescence in planar-aligned liquid crystal hosts Planar-aligned cholesterics with 1-D photonic bandgap structure can provide circularly polarized fluorescence of definite handedness even for emitters without dipole moments Planar-aligned cholesteric Transmitted LH light Planar-aligned nematics can provide linearly polarized fluorescence in definite direction for emitters with molecular dipoles Po Reflected RH light Incident unpolarized light λ o = n av P o, Δλ = λ o Δn/n av, where pitch P o = 2a (a is a period of the structure); n av = (n e + n o )/2; Δn = n e -n o.

28 Selective reflection curves of 1-D photonic bandgap planar-aligned dye-doped cholesteric layers (mixtures of E7 and CB15) Transmittance (%) Spectrophotometer Data for RHCP light (selective reflection curves) and LHCP light (blue line) 579 nm emission wavelength Wavelength (nm)

Images of Single Molecule Fluorescence 16 110.7 147.

25 2 μm 0 0 25 50 75 100 125 150 175 200 DiI dye on

29 Images of Single Molecule Fluorescence μm 25 2 μm DiI dye on bare glass slip CdSe quantum dots on bare glass slip

Single DiI dye molecule fluorescence in 1-D photonic bandgap cholesteric liquid crystal host 3 184.0 140.

30 Single DiI dye molecule fluorescence in 1-D photonic bandgap cholesteric liquid crystal host μm Forw. or APD Backw.or APD

31 Fluorescence of single quantum dots

32 Typical photon coincidence histogram coincidence events n(t) time interval t (ns)

33 Fluorescence decay of DiI in CLC coincidences ns

34 Acknowledgements The authors acknowledge the support by the U.S. Army Research Office under Award No. DAAD , National Science Foundation Awards ECS , EEC , PHY , University of Rochester Kauffman Initiative. The authors thank L. Novotny, A. Lieb, J. Howell, T. Brown, R. Boyd, A. Schmid, P. Adamson, S. Bentley for advice and help, C. Supranovitz, D. Esterly and S. Schrauth for assistance.

Quantum Optics and Quantum Information Laboratory Review

Quantum Optics and Quantum Information Laboratory Review Fall 2010 University of Rochester Instructor: Dr. Lukishova Joshua S. Geller Outline Lab 1: Entanglement and Bell s Inequalities Lab 2: Single Photon