Lab 1 Entanglement and Bell s Inequalities

Quantum Optics Lab Review Justin Winkler

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)

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

Theory

Measured and Theoretical Probabilities

CSHS Inequality Quantum mechanics predicts violation at certain angles, allowing a maximum S value of 2.82843

Experimental Setup

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

Bell s inequality was violated Predicted S = 2.828

Additional Results Predicted S = 2.497

Lab 2: Single Photon Interference

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

Double Slit Diffraction

Diffraction Pattern

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

Double Slit Apparatus

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

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

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

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

Fringe Visibility Fringe Visibility = Max - Min Max + Min

Fringe Visibility Results

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

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.

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

Experimental Setup

CCD Imaging

Confocal Microscope Scans

Scan Close-up

Antibunching Histogram

Histogram Without Antibunching

We Saw Antibunching!

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.

Scan With Photonic Bandgap Material

Antibunching With Photonic Bandgap Material

Fluorescence Lifetime

The End

Questions?

Phase Shift from BBO Crystals

Fringe Visibility Results

Delay Characterization 61.81 ns

Spontaneous Parametric Down-Conversion

SPDC Ring Imaged With CCD Camera

Single Counts

Horizontal Waveplate Alignment

Vertical Waveplate Alignment