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SUMMARY:Hong-Ou-Mandel effect under partial time reversal: a destructive i
 nterference effect in the amplification of light - Nicolas J. Cerf (Univer
 site Libre de Bruxelles
DTSTART:20190509T131500Z
DTEND:20190509T141500Z
UID:TALK123997@talks.cam.ac.uk
CONTACT:Johannes Bausch
DESCRIPTION:In the usual\, predictive approach of quantum mechanics\, one 
 deals with the preparation of a quantum system followed by its time evolut
 ion and ultimately its measurement. In the retrodictive approach of quantu
 m mechanics\, one postselects the instances where a particular measurement
  outcome was observed and considers the probability of the preparation var
 iable conditionally on this outcome. This can be interpreted as if the act
 ually measured state had propagated backwards in time to the preparer. I w
 ill present an intermediate picture\, called _partial time reversal_\, whe
 re a composite system propagates partly forwards and partly backwards in t
 ime. As a striking application\, I will focus on the simplest 2-mode linea
 r-optical component\, namely a beam splitter\, and show that it transforms
  into a two-mode squeezer under partial time reversal. More generally\, by
  building on the generating function of the matrix elements of Gaussian un
 itaries in Fock basis\, I will build simple recurrence equations that are 
 obeyed by the multiphoton transition probabilities (both for the passive a
 nd active linear coupling between two bosonic modes). These recurrence equ
 ations exhibit an interferometric suppression term which generalizes the H
 ong-Ou-Mandel effect for more than two indistinguishable photons impinging
  on a beam splitter of transmittance 1/2. It also exhibits an unexpected 2
 -photon suppression effect in an optical parametric amplifier of gain 2 or
 iginating from the _timelike_ indistinguishability between the input and o
 utput photons (it is the partial time-reversed version of the usual _space
 like_ indistinguishability that is at work in the Hong-Ou-Mandel effect).
LOCATION:MR13\, Centre for Mathematical Sciences\, Wilberforce Road\, Camb
 ridge
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