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.

February 8, 2007
Thursday, 12:30 PM to 2 PM

Rolando Somma ,
P-21

Quantum Metrology: Optimal Quantum Measurements

Abstract

The standard method to obtain expectation values of observables and unitary operators of a quantum system consists of preparing many copies of the desired state, and measuring the corresponding quantity by coupling the quantum system to an apparatus. The precision of the measured value using this method is known to scale as 1/sqrt(N), where N indicates the number of copies (experiments). I will show that, with a minimal prior knowledge about the operator whose expectation value is to be measured, such a precision can be increased to 1/N. For this purpose, I will consider different variations of the phase estimation algorithm according to the quantity that is to be measured. These algorithms are particularly useful for simulating quantum systems on quantum computers, enabling efficient measurement of observables and correlation functions. In particular, I will describe simple single parameter estimation and reference-frame alignment methods, as these will potentially be implemented in the near future on the ion-trap device at the Lab.