Lab Home | Phone | Search
Center for Nonlinear Studies  Center for Nonlinear Studies
 Home 
 People 
 Current 
 Postdocs 
 Visitors 
 Students 
 Research 
 Publications 
 Conferences 
 Workshops 
 Sponsorship 
 Talks 
 Seminars 
 Postdoc Seminars Archive 
 Quantum Lunch 
 Quantum Lunch Archive 
 P/T Colloquia 
 Archive 
 Ulam Scholar 
 
 Postdoc Nominations 
 Students 
 Student Program 
 Visitors 
 Description 
 Past Visitors 
 Services 
 General 
 
 History of CNLS 
 
 Maps, Directions 
 CNLS Office 
 T-Division 
 LANL 
 
Thursday, October 08, 2009
12:30 PM - 1:30 PM
T-DO Conference Room

Quantum Lunch

Quantum-limited metrology: Dynamics vs. entanglement

Carl Caves
Department of Physics and Astronomy, University of New Mexico

Questions about quantum limits on measurement precision were once viewed from the perspective of how to reduce or avoid the effects of the quantum noise that is a consequence of the uncertainty principle. With the advent of quantum information science came a paradigm shift to proving rigorous bounds on measurement precision. These bounds have been interpreted as saying, first, that the best achievable sensitivity scales as 1/N, where N is the number of particles one has available for a measurement and, second, that the only way to achieve this Heisenberg-limited sensitivity is to use quantum entanglement. I will review these results and introduce a new perspective based on using nonlinear quantum dynamics to improve sensitivity. Using quadratic couplings of N particles to a parameter to be estimated, one can achieve sensitivities that scale as 1/N^2 if one uses entanglement, but even in the absence of any entanglement at any time during the measurement protocol, one can achieve a super-Heisenberg scaling of 1/N^{3/2}. Such sensitivity scalings might be achieved in Bose-Einstein condensates or in nanomechanical resonators.

Host: Wojciech Zurek