Experimental Issues in Quantum Measurement

1
Experimental Issues in Quantum Measurement
Lectures Tuesday, 10-11, Kleiner Hörsaal
Aephraim Steinberg
(auf Englisch, es tut mir leid)

• Why does one thing happen and not another?
• When is a quantum measurement?
• Does a measurement necessarily disturb the
  system, and how?
• What can we say about an observable before we
  measure it?
• Does a wave function describe a single particle,
  or only an ensemble?
• Is a wave function a complete description of a
  single particle?
• Can we predict the past?

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Atoms falling out of a lattice trap
As the trap is lowered, each quantum state falls
out at a different time we can see by eye how
many atoms were in each energy eigenstate.
3
The Wigner quasiprobability function
...combining many such measurements, we can
completely describe the quantum state of the
atoms.
P(0,0) lt 0 ?!
4
Some topics well cover

• Must collapse really happen?
• alternate pictures of measurements and
  correlations
• How much can we say about the past?
• weak measurements and postselection...
• Can we measure the entire state of a particle?
• density-matrix and Wigner function reconstruction
• Can we distinguish between indistinguishable
  things?
• non-orthogonal state discrimination
• Are there different things we can never
  distinguish between?
• different preparations of identical density
  matrices
• Can we measure something without interacting
  with it?
• Vaidmans bomb experiment
• Can we undo the disturbance introduced by a
  measurement?
• The quantum eraser
• Can we use the measurement process to accomplish
  tasks?
• Measurement-induced nonlinearity, LOQC

LECTURES TUESDAYS 10-11, Kleiner Hörsaal