22 research outputs found
Quantum time transfer for freespace quantum networking
Timing requirements for long-range quantum networking are driven by the
necessity of synchronizing the arrival of photons, from independent sources,
for Bell-state measurements. Thus, characteristics such as repetition rate and
pulse duration influence the precision required to enable quantum networking
tasks such as teleportation and entanglement swapping. Some solutions have been
proposed utilizing classical laser pulses, frequency combs, and bi-photon
sources. In this article, we explore the utility of the latter method since it
is based upon quantum phenomena, which makes it naturally covert, and
potentially quantum secure. Furthermore, it relies on relatively low technology
quantum-photon sources and detection equipment, but provides picosecond timing
precision even under high loss and high noise channel conditions representative
of daytime space-Earth links. Therefore, this method is potentially relevant
for daytime space-Earth quantum networking and/or providing high-precision
secure timing in GPS denied environments
Practical Approach to Extending Baselines of Telescopes using Continuous-Variable Quantum Information
Interferometric telescopes are instrumental for the imaging of distant
astronomical bodies, but optical loss heavily restricts how far telescopes in
an array can be placed from one another, leading to a bottleneck in the
resolution that can be achieved. An entanglement-assisted approach to this
problem has been proposed by Gottesman, Jennewein, and Croke (GJC12) [Physical
Review Letters, 109(7):070503, July 2011], as a possible solution to the issue
of optical loss if the entangled state can be distributed across long distances
by employing a quantum repeater network. In this paper, we propose an
alternative entanglement-assisted scheme that interferes a two-mode squeezed
vacuum state with the astronomical state and then measures the resulting state
by means of homodyne detection. We use a continuous-variable approach and
compute the Fisher information with respect to the mutual coherence of the
astronomical source. We show that when the Fisher information is observed
cumulatively at the rate at which successful measurements can be performed, our
proposed scheme does not outperforms the traditional direct detection approach
or the entanglement-assisted approach of GJC12.Comment: 9 pages, 2 figure
Spatial multimode structure of atom-generated squeezed light
We investigated the spatial distribution of quantum fluctuations in a squeezed vacuum field, generated via polarization self-rotation (PSR) interaction of an ensemble of Rb atoms and a strong near-resonant linearly polarized laser field. We found that the noise suppression is greatly effected by the transverse profile of a spatial mask, placed in both the squeezed field and the local oscillator, as well as its position along the focused beam near the focal point. These observations indicate the spatial multimode structure of the squeezed vacuum field. We have developed a theoretical model that describes the generation of higher-order Laguerre-Gauss modes as a result of PSR light-atom interaction. The prediction of this model is in a good qualitative agreement with the experimental measurements
Two-Way Quantum Time Transfer: A Method for Daytime Space-Earth Links
Remote clock synchronization is crucial for many classical and quantum
network applications. Current state-of-the-art remote clock synchronization
techniques achieve femtosecond-scale clock stability utilizing frequency combs,
which are supplementary to quantum-networking hardware. Demonstrating an
alternative, we synchronize two remote clocks across our freespace testbed
using a method called two-way quantum time transfer (QTT). In one second we
reach picosecond-scale timing precision under very lossy and noisy channel
conditions representative of daytime space-Earth links with commercial
off-the-shelf quantum-photon sources and detection equipment. This work
demonstrates how QTT is potentially relevant for daytime space-Earth quantum
networking and/or providing high-precision secure timing in GPS-denied
environments.Comment: arXiv admin note: text overlap with arXiv:2211.0073