Lecture 10 Jeffrey H. Shapiro Optical and Quantum Communications - PDF document

October 13, 2016 6.453 Quantum Optical Communication Lecture 10 Jeffrey H. Shapiro Optical and Quantum Communications Group www.rle.mit.edu/qoptics 6.453 Quantum Optical Communication - Lecture 10 § Announcements § Turn in problem set 5 § Pick up problem set 5 solutions, problem set 6, lecture notes, slides § Single-Mode Photodetection § Signatures of non-classical light § Squeezed-state waveguide tap 2 www.rle.mit.edu/qoptics 1

Single-Mode Semiclassical Photodetection § Photon-Units Classical Field: § Direct Detection: given , is Poisson with mean a § Homodyne Detection: given , a § Heterodyne Detection: given , a 3 www.rle.mit.edu/qoptics Single-Mode Quantum Photodetection § Photon-Units Field Operator: for § Direct Detection: measurement § Homodyne Detection: measurement § Heterodyne Detection: measurement 4 www.rle.mit.edu/qoptics 2

Single-Mode Random Fields: Classical vs. Quantum § Classical Field: complex random variable § Measurement variances § Quantum Field: density operator of the excited mode § Measurement variances where 5 www.rle.mit.edu/qoptics Signatures of Non-Classical Light § “ Classical Light ” = random mixture of coherent states § Sub-Poissonian Statistics: § Quadrature-Noise Squeezing: § Heterodyne-Detection Statistics Determine 6 www.rle.mit.edu/qoptics 3

Optical Waveguide Tap — Semiclassical § Coupler is a beam splitter Fused Fiber Coupler § Tap input is zero § Homodyne SNR at signal input § Homodyne SNR at signal output § Homodyne SNR at tap output 7 www.rle.mit.edu/qoptics Optical Waveguide Tap — Quantum § Coupler is a beam splitter Fused Fiber Coupler § Tap input is in squeezed vacuum § Homodyne SNR at signal input § Homodyne SNR at signal output § Homodyne SNR at tap output 8 www.rle.mit.edu/qoptics 4

Optical Waveguide Tap: SNR Tradeoff 9 www.rle.mit.edu/qoptics Non-Ideal Quantum Photodetection § Quantum Efficiency : § Direct Detection: measurement § Homodyne Detection: measurement § Heterodyne Detection: measurement 10 www.rle.mit.edu/qoptics 5

Loss is a Problem for Squeezed States 11 www.rle.mit.edu/qoptics Coming Attractions: Lecture 11 § Lecture 11: Single-Mode and Two-Mode Linear Systems § Attenuators § Phase-Insensitive Amplifiers § Phase-Sensitive Amplifiers 12 www.rle.mit.edu/qoptics 6

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