Exploring the multimode structure of atomgenerated squeezed light

Exploring the multi-mode structure of atom-generated squeezed light Melissa Guidry Advisor: Eugeniy Mikhailov Department of Physics, College of William & Mary

Outline • Introduction to light quadratures • Squeezed light • Applications • Squeezing through atoms • Experiment • Noise detection • Pump beam mode optimization • Local oscillator mode shaping • Conclusions and outlook • Spatial photon statistics 12/7/2020 2

Quantum fluctuations Quantization of the EM-field Quadrature operators Non-commutative: 3

Squeezed vacuum Applications: • Quantum probe in EIT-based quantum memory • Enhanced laser interferometry (GEO 600, LIGO) • Precision metrology 4

Applications Interferometric gravitational wave detectors Atomic clocks 2 d. B squeezing: 26% sensitivity improvement 1 Absorption spectroscopy 1 H. Grote et al. Phys. 12/7/2020 Rev. Lett. 110, 181101 (2013). 5

Squeezing measurement • Polarization self-rotation • Predicted squeezing: -8 d. B A. B. Matsko, I. Novikova, G. R. Welch, D. Budker, D. F. Kimball, and S. M. Rochester. Phys. Rev. A 66, 043815 (2002) • Best squeezing: -3 d. B S. Barreiro, P. Valente, H. Failache, and A. Lezama Phys. Rev. A 84, 033851 (2011) • Our squeezing: -2. 7 d. B -1 0 +1 6

Homodyne detection 12/7/2020 7

SMPM fiber GP L L Rb 87 -cell Diode laser Spectrum analyzer BPD 50/50 SMPM M SLM GP Ph. R BPD Ph. R PBS Single-mode polarization-maintaining Mirror Spatial light modulator Glenn Polarizer Phase-retarding plate Balanced photodiodes 8

Mode structure M. Zhang, et al. Phys. Rev. A, 93: 013853, 2016. Squeezed vacuum 87 Rb-cell LO 12/7/2020 9

Multi-mode generation Local oscillator imaging Mi Zhang, R. Nicholas Lanning, Zhihao Xiao, Jonathan P. Dowling, Irina Novikova, and Eugeniy E. Mikhailov, Phys. Rev. A 93, 01385 (2016) • Complex spatial structure of the squeezed field • Local oscillator and vacuum field both experience spatial dependence on atomic density • Spatial distribution of pump beam influences squeezing Increasing atomic density 10

12/7/2020 11

Laguerre-Gaussian (LG) modes • Higher order mode generation • Power moved from Gaussian mode to higher order LG modes 12/7/2020 12

Spatial light modulator V. Nikolenko, et al. Desired image 12/7/2020 Phase mask Fluorescence 13

L L 87 Rb-cell SLM Detection Squeezing Pump beam mode structure optimization: 1. Set an initial phase mask 2. Measure squeezing 3. Alter the phase mask 4. Measure squeezing 5. Reject or accept move 12/7/2020 14

Spatial optimization 15

Pump beam optimization 16

Local oscillator optimization SLM Original squeezing: -1. 8 d. B Squeezing with SLM turned on: -1. 0 d. B L Rb 87 -cell No improvement was observed. M Possible explanation: • Voltage applied to liquid crystals induces oscillations • Oscillating crystals Phase oscillations • Induces cycling through quadratures, averaging greater noise 17

Optimization summary Rb 87 -cell SLM Reshaping the pump beam using the SLM can improve squeezing under some conditions. Rb 87 -cell SLM Reflection off of the SLM deteriorates squeezing in the on state. Looking at spatial squeezing directly? • • Quantum noise-limited camera Measure photon statistics 18

12/7/2020 19

Four distinct noise lobes 12/7/2020 20

12/7/2020 21

Outlook • • • AOM shutter Camera kinetic mode subtraction with knife blade Low frequency removal Camera artifact removal Spatial correlations in noise Figure source: africa-wildlifedetective. com 12/7/2020 22

Acknowledgements Louisiana State University William & Mary Quantum Optics Group Jonathan P. Dowling This project is supported by AFOSR grant FA 9550 -13 -1 -0098, MAG is supported by the VSGC. R. Nicholas Lanning Zhihao Xiao 23