10 research outputs found
Stochastic metrology and the empirical distribution
We study the problem of parameter estimation in time series stemming from
general stochastic processes, where the outcomes may exhibit arbitrary temporal
correlations. In particular, we address the question of how much Fisher
information is lost if the stochastic process is compressed into a single
histogram, known as the empirical distribution. As we show, the answer is
non-trivial due to the correlations between outcomes. We derive practical
formulas for the resulting Fisher information for various scenarios, from
generic stationary processes to discrete-time Markov chains to continuous-time
classical master equations. The results are illustrated with several examples.Comment: 16 pages, 8 figures, 1 tabl
Assessing the quality of a network of vector-field sensors
An experiment consisting of a network of sensors can endow several advantages
over an experiment with a single sensor: improved sensitivity, error
corrections, spatial resolution, etc. However, there is often a question of how
to optimally set up the network to yield the best results. Here, we consider a
network of devices that measure a vector field along a given axis; namely for
magnetometers in the Global Network of Optical Magnetometers for Exotic physics
searches (GNOME). We quantify how well the network is arranged, explore
characteristics and examples of ideal networks, and characterize the optimal
configuration for GNOME. We find that by re-orienting the sensitive axes of
existing magnetometers, the sensitivity of the network can be improved by
around a factor of two.Comment: 7 pages, 2 figures, 2 table
Optomechanical Analogy for Toy Cosmology with Quantized Scale Factor
The simplest cosmology—the Friedmann–Robertson–Walker–Lemaître (FRW) model— describes a spatially homogeneous and isotropic universe where the scale factor is the only dynamical parameter. Here we consider how quantized electromagnetic fields become entangled with the scale factor in a toy version of the FRW model. A system consisting of a photon, source, and detector is described in such a universe, and we find that the detection of a redshifted photon by the detector system constrains possible scale factor superpositions. Thus, measuring the redshift of the photon is equivalent to a weak measurement of the underlying cosmology. We also consider a potential optomechanical analogy system that would enable experimental exploration of these concepts. The analogy focuses on the effects of photon redshift measurement as a quantum back-action on metric variables, where the position of a movable mirror plays the role of the scale factor. By working in the rotating frame, an effective Hubble equation can be simulated with a simple free moving mirror
A machine learning algorithm for direct detection of axion-like particle domain walls
The Global Network of Optical Magnetometers for Exotic physics searches (GNOME) conducts an experimental search for certain forms of dark matter based on their spatiotemporal signatures imprinted on a global array of synchronized atomic magnetometers. The experiment described here looks for a gradient coupling of axion-like particles (ALPs) with proton spins as a signature of locally dense dark matter objects such as domain walls. In this work, stochastic optimization with machine learning is proposed for use in a search for ALP domain walls based on GNOME data. The validity and reliability of this method were verified using binary classification. The projected sensitivity of this new analysis method for ALP domain-wall crossing events is presented.11Nsciescopu
Stochastic fluctuations of bosonic dark matter
Numerous theories extending beyond the standard model of particle physics
predict the existence of bosons that could constitute the dark matter (DM)
permeating the universe. In the standard halo model (SHM) of galactic dark
matter the velocity distribution of the bosonic DM field defines a
characteristic coherence time . Until recently, laboratory experiments
searching for bosonic DM fields have been in the regime where the measurement
time significantly exceeds , so null results have been interpreted
as constraints on the coupling of bosonic DM to standard model particles with a
bosonic DM field amplitude fixed by the average local DM density.
However, motivated by new theoretical developments, a number of recent searches
probe the regime where . Here we show that experiments operating in
this regime do not sample the full distribution of bosonic DM field amplitudes
and therefore it is incorrect to assume a fixed value of when
inferring constraints on the coupling strength of bosonic DM to standard model
particles. Instead, in order to interpret laboratory measurements (even in the
event of a discovery), it is necessary to account for the stochastic nature of
such a virialized ultralight field (VULF). The constraints inferred from
several previous null experiments searching for ultralight bosonic DM were
overestimated by factors ranging from 3 to 10 depending on experimental
details, model assumptions, and choice of inference framework.Comment: Supplementary material was not compiled in previous versio
Intensity interferometry for ultralight bosonic dark matter detection
Ultralight bosonic dark matter (UBDM) can be described by a classical
wave-like field oscillating near the Compton frequency of the bosons. If a
measurement scheme for the direct detection of UBDM interactions is sensitive
to a signature quadratic in the field, then there is a near-zero-frequency (dc)
component of the signal. Thus, a detector with a given finite bandwidth can be
used to search for bosons with Compton frequencies many orders of magnitude
larger than its bandwidth. This opens the possibility of a detection scheme
analogous to Hanbury Brown and Twiss intensity interferometry. Assuming that
the UBDM is virialized in the galactic gravitational potential, the random
velocities produce slight deviations from the Compton frequency. These result
in stochastic fluctuations of the intensity on a time scale determined by the
spread in kinetic energies. In order to mitigate ubiquitous local low-frequency
noise, a network of sensors can be used to search for the stochastic intensity
fluctuations by measuring cross-correlation between the sensors. This method is
inherently broadband, since a large range of Compton frequencies will yield
near-zero-frequency components within the sensor bandwidth that can be searched
for simultaneously. Measurements with existing sensor networks have sufficient
sensitivity to search experimentally unexplored parameter space.Comment: 10 pages, 4 figures. Supplementary material included after the
reference
Search for topological defect dark matter with a global network of optical magnetometers
Ultralight bosons such as axion-like particles are viable candidates for dark matter. They can form stable, macroscopic field configurations in the form of topological defects that could concentrate the dark matter density into many distinct, compact spatial regions that are small compared with the Galaxy but much larger than the Earth. Here we report the results of the search for transient signals from the domain walls of axion-like particles by using the global network of optical magnetometers for exotic (GNOME) physics searches. We search the data, consisting of correlated measurements from optical atomic magnetometers located in laboratories all over the world, for patterns of signals propagating through the network consistent with domain walls. The analysis of these data from a continuous month-long operation of GNOME finds no statistically significant signals, thus placing experimental constraints on such dark matter scenarios