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SUMMARY:Quantum Complexity in Ultracold Quantum Systems - Lincoln D. Carr 
 (Colorado School of Mines)
DTSTART:20150709T130000Z
DTEND:20150709T140000Z
UID:TALK60119@talks.cam.ac.uk
CONTACT:6270
DESCRIPTION:Ultracold quantum simulators have proven a tremendous success.
   These analog quantum computers have allowed us to explore diverse quantu
 m many-body phenomena from quantum phase transitions to the Kibble-Zurek m
 echanism to many-body localization.  We propose a new direction for analog
  quantum computations\, quantum complexity.  Despite hundreds of thousands
  of empirical examples of complexity ranging from complex networks like th
 e internet to diverse mixed geometry microbial communities like the microb
 iome found in the human gut\, we have no first principles theory of comple
 xity – we don’t know why nature seems to prefer complexity.  Moreover\
 , unlike the other senses of the word “macroscopicity” we don’t have
  a good sense of how classical complexity\, associated with macroscopic cl
 assical systems\, results from the underlying quantum dynamics – so we d
 on’t know where this preference first appears at the quantum level.  In 
 this talk\, we principally explore two topics in this untested regime of q
 uantum mechanics.  First\, we propose a new set of quantum measures for co
 mplex quantum dynamics\, namely quantum mutual information complex network
 s.  As a proof of principle\, we show that complex network measures like c
 lustering reproduce and improve upon traditional correlation-based measure
 s for the critical point of quantum phase transitions in transverse Ising 
 and Bose-Hubbard models.  Second\, we identify new concrete regimes of qua
 ntum complexity in quantum simulators implementing molecular Hubbard Hamil
 tonians.  For singlet sigma molecules we calculate specific parameter sets
  for five kinds of molecules either already quantum degenerate and at unit
  filling in optical lattices in lab experiments\, or close to quantum dege
 neracy: LiCs\, NaK\, RbCs\, KRb\, RbCs\, and LiNa.  Finally\, we briefly o
 utline progress in two other areas of quantum complexity: new regimes acce
 ssible in many-body symmetric top molecular systems\, and quantum games of
  life
LOCATION:Ryle Seminar (Rutherford 930)
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