MIT OpenCourseWarehttp://ocw.mit.edu 6.453 Quantum Optical Communication Spring 2009 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms.October 14, 2008Optical and Quantum Communications Groupwww.rle.mit.edu/qoptics6.453 Quantum Optical CommunicationLecture 10Jeffrey H. Shapiro2www.rle.mit.edu/qoptics6.453 Quantum Optical Communication - Lecture 10! Announcements! Turn in problem set 5! Pick up problem set 4 graded, problem set 5 solution, problem set 6,lecture notes, slides! Single-Mode Photodetection! Signatures of non-classical light! Squeezed-state waveguide tap3www.rle.mit.edu/qopticsSingle-Mode Semiclassical Photodetection! Photon-Units Classical Field:! Direct Detection: given , is Poisson with mean! Homodyne Detection: given ,! Heterodyne Detection: given ,4www.rle.mit.edu/qopticsSingle-Mode Quantum Photodetection! Photon-Units Field Operator:for! Direct Detection: measurement! Homodyne Detection: measurement! Heterodyne Detection: measurement5www.rle.mit.edu/qopticsSingle-Mode Random Fields: Classical vs. Quantum! Classical Field: complex random variable! Measurement variances! Quantum Field: density operator of the excited mode! Measurement varianceswhere6www.rle.mit.edu/qopticsSignatures of Non-Classical Light! “Classical Light” = random mixture of coherent states! Sub-Poissonian Statistics:! Quadrature-Noise Squeezing:! Heterodyne-Detection Statistics Determine7www.rle.mit.edu/qopticsOptical Waveguide Tap —!Semiclassical! Coupler is a beam splitter! Tap input is zero! Homodyne SNR at signal input! Homodyne SNR at signal output! Homodyne SNR at tap outputFused Fiber Coupler8www.rle.mit.edu/qopticsOptical Waveguide Tap —!Quantum! Coupler is a beam splitter! Tap input is in squeezed vacuum! Homodyne SNR at signal input! Homodyne SNR at signal output! Homodyne SNR at tap outputFused Fiber Coupler9www.rle.mit.edu/qopticsOptical Waveguide Tap: SNR Tradeoff10www.rle.mit.edu/qopticsNon-Ideal Quantum Photodetection! Quantum Efficiency :! Direct Detection: measurement! Homodyne Detection: measurement! Heterodyne Detection: measurement11www.rle.mit.edu/qopticsLoss is a Problem for Squeezed States12www.rle.mit.edu/qopticsComing Attractions: Lecture 11! Lecture 11:Single-Mode and Two-Mode Linear Systems! Attenuators! Phase-Insensitive Amplifiers! Phase-Sensitive
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