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Quantum Institute : 2009 Quantum Lunch Seminar Schedule


  • Coordinator
    Diego Dalvit
  • Quantum Lunch Location:
    T-Division Conference Room, TA-3,
    Building 123, Room 121

Quantum Institute: Visitor Schedule

The Quantum Lunch is regularly held on Thursdays in the Theoretical Division Conference Room, TA-3, Building 123, Room 121.
For more information, contact Diego Dalvit.
To add your name to the Quantum Lunch email list, contact Charlotte Carter

Thursday, October 8, 2009
12:30 PM - 2:00 PM

Speaker: Carlton M. Caves, University of New Mexico

Technical Host: Wojciech Zurek

TOPIC: Quantum-limited metrology: Dynamics vs. entanglement

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.

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