F. Y. Khalili | Searcharxiv

arXiv2026

Squeezing for dispersive readout of NV magnetometer

Nitrogen vacancy centers in diamond have established themselves as good sensing element for various type of sensors. In particular magnetometers based on diamond impurities are quickly developing and are already on the market. Yet, optical readout in these systems complicates system design. Recently schemes of dispersive readout of nitrogen vacancy spin state using high finesse dielectric cavities for microwave field were proposed, which do not use the optical readout scheme. However, only shot noise based estimates were so far done for sensitivity of these devices. Here we provide detailed analysis of various practically relevant noise and loss sources for such a system. Furthermore, we consider the possibility of using the squeezing quantum state of the probing microwave field and show it allows to improve the device performance even at room temperature.

quant-ph↗

arXiv2016

On universal decoherence under gravity: a perspective through the Equivalence Principle

In Nature Phys. 11, 668 (2015) (Ref. [1]), a composite particle prepared in a pure initial quantum state and propagated in a uniform gravitational field is shown to undergo a decoherence process at a rate determined by the gravitational acceleration. By assuming Einstein's Equivalence Principle to be valid, we demonstrate, first in a Lorentz frame with accelerating detectors, and then directly in the Lab frame with uniform gravity, that the dephasing between the different internal states arise not from gravity but rather from differences in their rest mass, and the mass dependence of the de Broglie wave's dispersion relation. We provide an alternative view to the situation considered by Ref. [1], where we propose that gravity plays a kinematic role in the loss of fringe visibility by giving the detector a transverse velocity relative to the particle beam; visibility can be easily recovered by giving the screen an appropriate uniform velocity. We finally propose that dephasing due to gravity may in fact take place for certain modifications to the gravitational potential where the Equivalence Principle is violated.

quant-ph↗