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 16, 2008Optical and Quantum Communications Groupwww.rle.mit.edu/qoptics6.453 Quantum Optical CommunicationLecture 11Jeffrey H. Shapiro2www.rle.mit.edu/qoptics6.453 Quantum Optical Communication - Lecture 11! Announcements! Pick up lecture notes, slides! Single-Mode Photodetection! Squeezed-state waveguide tap — reprise! Single-Mode Linear Systems! Attenuators! Phase-Insensitive Amplifiers3www.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 Coupler4www.rle.mit.edu/qopticsOptical Waveguide Tap: SNR Tradeoff5www.rle.mit.edu/qopticsNon-Ideal Quantum Photodetection! Quantum Efficiency :! Direct Detection: measurement! Homodyne Detection: measurement! Heterodyne Detection: measurement6www.rle.mit.edu/qopticsNon-Ideal Quantum Photodetection:! Direct Detection of Number State :! Homodyne Detection of Squeezed State :7www.rle.mit.edu/qopticsLoss is a Problem for Squeezed States8www.rle.mit.edu/qopticsSingle-Mode Linear Systems: the Attenuator! Classical Attenuation! Noiseless attenuation is possible9www.rle.mit.edu/qopticsSingle-Mode Linear Systems: the Amplifier! Classical Amplification! Noiseless amplification is possible10www.rle.mit.edu/qopticsSingle-Mode Linear Systems: Quantum Case! Input and Output are Photon Annihilation Operators:! Quantum Attenuator Cannot Obey! Quantum Amplifier Cannot Obey! Loss and Gain Require Additional Quantum Noise:to preserve the Heisenberg Uncertainty Principle11www.rle.mit.edu/qopticsSingle-Mode Linear Systems: Quantum Case! Quantum Attenuation! Quantum Amplification12www.rle.mit.edu/qopticsSingle-Mode Linear Systems: Quantum Case! Attenuator with Coherent-State and Vacuum-State :! Amplifier with Coherent-State and Vacuum-State :13www.rle.mit.edu/qopticsComing Attractions: Lecture 12! Lecture 12:Single-Mode and Two-Mode Linear Systems! Phase-Insensitive Amplifiers! Phase-Sensitive Amplifiers!
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