Timedependent Hamiltonian estimation for Doppler velocimetry of trapped ions
Abstract
The time evolution of a closed quantum system is connected to its Hamiltonian through Schroedinger's equation. The ability to estimate the Hamiltonian is critical to our understanding of quantum systems, and allows optimization of control. Though spectroscopic methods allow timeindependent Hamiltonians to be recovered, for timedependent Hamiltonians this task is more challenging. Here, using a single trapped ion, we experimentally demonstrate a method for estimating a timedependent Hamiltonian of a single qubit. The method involves measuring the time evolution of the qubit in a fixed basis as a function of a timeindependent offset term added to the Hamiltonian. In our system the initially unknown Hamiltonian arises from transporting an ion through a static, nearresonant laser beam. Hamiltonian estimation allows us to estimate the spatial dependence of the laser beam intensity and the ion's velocity as a function of time. This work is of direct value in optimizing transport operations and transportbased gates in scalable trapped ion quantum information processing, while the estimation technique is general enough that it can be applied to other quantum systems, aiding the pursuit of high operational fidelities in quantum control.
 Publication:

arXiv eprints
 Pub Date:
 September 2015
 DOI:
 10.48550/arXiv.1509.07083
 arXiv:
 arXiv:1509.07083
 Bibcode:
 2015arXiv150907083D
 Keywords:

 Quantum Physics;
 Physics  Atomic Physics;
 Physics  Optics
 EPrint:
 10 pages, 8 figures