Lab 1 Entanglement and Bell s Inequalities

Transcription

1 Quantum Optics Lab Review Justin Winkler

2 Lab 1 Entanglement and Bell s Inequalities

3 Entanglement Wave-functions are non-separable Measurement of state of one particle alters the state of the other particle Entanglement proposed in EPR paper (1935) Believed this couldn t happen Bell s inequalities show occurrence of entanglement (proposed by J. S. Bell, 1964)

4 Bell s Inequality Inequality does not describe any particular physical quantity Trivially satisfied for classical objects Bell s inequalities allow experimental testing of interpretation of quantum mechanics Bell s theorem no theory of local hidden variables can fully reproduce the predictions of quantum mechanics

5 Theory

6 Measured and Theoretical Probabilities

7 CSHS Inequality Quantum mechanics predicts violation at certain angles, allowing a maximum S value of

8 Experimental Setup

9 Coincident Photon Counts Polarizer A held constant, polarizer B rotated Expected cosine squared dependence

10 Bell s inequality was violated Predicted S = 2.828

11 Additional Results Predicted S = 2.497

12 Lab 2: Single Photon Interference

13 Lab 2 Structure Two Parts Double Slit Diffraction Wave-Particle Duality Single photon diffraction Used attenuated laser source Mach-Zehnder Interferometer Which-way information Also used attenuated laser source

14 Double Slit Diffraction

15 Diffraction Pattern

16 Wave-Particle Duality Light has wave-like and particle-like like properties Wave Diffraction Interference Particle Photoelectric effect Photons Antibunching Single photons are still expected to display interference effects

17 Double Slit Apparatus

18 Double Slit Results 4 orders of attenuation Average of 0.94 meters between photons 0.1 second exposure time

19 Build Up of Interference Pattern Attenuation = 0.8 * 10-5 Photon Separation = 11.7 m 0.5 Seconds 1 Second 5 Seconds

20 Mach-Zehnder Interferometer Light in different paths have orthogonal polarization Presence of which path information is controlled by analyzer polarizer

21 MZ Interferometer Pictures Analyzer Polarizer at 45 (no which way information) Analyzer Polarizer at 90 (which way information present)

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23 Fringe Visibility Fringe Visibility = Max - Min Max + Min

24 Fringe Visibility Results

25 Lab 3: Confocal Microscope Imaging of Single-Emitter Fluorescence Lab 4: Hanbury Brown & Twiss Setup, Photon Antibunching

26 Single Emitters and Photon Antibunching Attenuated lasers will sometimes produce bunches of photons which cannot be avoided. Single photon source requires single emitter that displays antibunching.

27 Quantum Dots Quantum dot - confines electrons in all directions Colloidal quantum dots - nanocrystals dispersed through a solution We prepared sample slides of colloidal quantum dots through spin coating Also used samples prepared by Luke Brissel

28 Experimental Setup

29 Experimental Setup

30 CCD Imaging

31 Confocal Microscope Scans

32 Scan Close-up

33 Antibunching Histogram

34 Histogram Without Antibunching

35 We Saw Antibunching!

36 Photonic Bandgap Material Photonic Crystals - Spatial periodicity on order of light wavelength Photonic Bandgap - No light passes in certain frequency range Cholesteric Liquid Crystals - Chiral crystals that suppress spontaneous emission in stop band and enhance near band edge.

37 Scan With Photonic Bandgap Material

38 Antibunching With Photonic Bandgap Material

39 Fluorescence Lifetime

40 The End

41 Questions?

42 Phase Shift from BBO Crystals

43 Fringe Visibility Results

44 Delay Characterization ns

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46 Spontaneous Parametric Down-Conversion

47 SPDC Ring Imaged With CCD Camera

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49 Single Counts

50 Horizontal Waveplate Alignment

51 Vertical Waveplate Alignment