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6.453 Quantum Optical Communication
Spring 2009
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September 4, 2008
6.453 Quantum Optical Communication
Lecture 1
Jeffrey H. Shapiro
Optical and Quantum Communications Group
www.rle.mit.edu/qoptics
6.453 Quantum Optical Communication — Lecture 1
! Handouts
! Syllabus, schedule/policy, probability chapter, lecture notes, slides,
problem set 1
! Sign-up on class list
! Introductory Remarks
! Subject organization
! Subject outline
! Technical Overview
! Optical eavesdropping tap — quadrature-noise squeezing
! Action at a distance — polarization entanglement
! Long-distance quantum state transmission — qubit teleportation
2
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Optical Homodyne Detection — Semiclassical
! Signal is weak, LO is strong
! Energy conservation
Balanced Homodyne Receiver
! Detectors are noisy square laws
! Output mean and variance
3
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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
4
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Quantum Homodyne Detection and Waveguide Tap
Balanced Homodyne Receiver
Fused Fiber Coupler
Homodyne SNR at tap output
Homodyne SNR at signal output
5
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Billiard-Ball Photons and the Poincaré Sphere
! Polarization of
-going photon:
! Poincaré sphere representation
!
polarization measurement
6
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Classical Correlation vs. Quantum Entanglement
! Classical-Correlated, Randomly-Polarized Photons
! Source produces
photon pair with
completely random
! Conditional probability given photon 1 is
instead of
! Maximally-Entangled Photons
! Source produces
photon pair with
completely random
! Conditional probability given photon 1 is
7
instead of
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Properties of Single-Photon Polarization States
! Polarization cannot be perfectly measured Æ
! ¨ Polarization cannot be perfectly cloned
! Photons can be lost in propagation:
8
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Photon Polarization States Can Be Teleported
Alice
Bob
9
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The Road Ahead: Problem Set 1, Lectures 2 and 3
! Problem Set 1
! Reviews of essential probability theory and linear algebra
! Lectures 2 and 3:
Fundamentals of Dirac-Notation Quantum Mechanics
!
!
!
!
!
Quantum systems
States as ket vectors
State evolution via Schrödinger’s equation
Quantum measurements — observables
Schrödinger picture versus Heisenberg picture
10
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