FREE COFFEE AND KRISPY KREME DONUTS
WHAT: TOPICS IN QUANTUM OPTICAL METROLOGY (PHD DEFENSE)
WHO: ARAVIND CHIRUVELLI (LSU)
WHEN: 3:40PM WED 26 AUG 09
WHERE: 435 NICH
ABSTRACT:
Quantum optical metrology deals with estimation of an unknown
parameter by
exploiting the non-classical properties of the light. The unknown
parameter
that we are trying to estimate is the optical phase. Precise
optical
phase
measurement has been a well-known problem and has many applications,
most
notably the gravitational wave detection.
In this thesis we investigate the interferometric measurement schemes.
We
consider the parity detection for a class of input states that have
been shown
to exhibit sub-shot noise limited phase estimate with their respective
detection schemes. Our results indicate that the parity detection
applies to all
these strategies with various input states and thus acts as a unified
detection
scheme towards the goal of interferometric phase estimates beyond the
shot-noise limit.
We also consider the performance of the so-called
optimal state with the canonical phase measurement
scheme that was proposed by Sanders and Milburn [Phys. Rev. Lett. 75,
2944 (1995)] in presence of photon loss. The model for photon loss is a
generic fictitious beam splitter and the analytical treatment requires
density matrix approach rather than the state-vector formalism.
We present full density-matrix calculations. Our
results indicate that, for a given amount of loss, the phase estimate
saturates but does not diverge as one would expect with increasing
the loss.
Finally, we study the continuous measurement and feedback schme with
optical homodyne detection for a single optical qubit. We found a
protocol that speeds up the rate of increase of the average purity of
the
system and generates a deterministic evolution for the purity in
the limit of strong feedback.