Time-of-flight refers to how long it takes for a photon to travel from point A to point B (see below). Knowing this travel time gives you a lot of potentially valuable information about what is happening between A and B, including:
The gravity gradient of the Earth or moon, relativistic effects, or even gravity waves, by measuring the distance between satellites.
Weather forecasting by calculating the pressure, temperature, CO2 concentration, and humidity in the atmosphere between cell towers and from satellites.
Network security by detecting line breaks or network intrusions in fiber optic cables.
Locating reference or rogue signals, or even a gunshot, using time difference of arrival.
Detecting and locating people behind walls using multiple wi-fi routers.
Obviously, time-of-arrival calculation requires very accurate synchronization between A and B. While this synchronization could be achieved by traditional means, Xairos' quantum clock synchronization (QCS) has added benefits as it directly measures the time a photon leaves A and arrives at B. It is fundamental to our protocol. This time-of-flight of individual photons can be used to glean even more valuable information about what is going on between A and B. Last Week's Theme: PNT? It should be TNP
Industry News
The recent European Radio Navigation Plan claims that “10% of the European Union (EU) GDP relies on the use of GNSS services", with an annual economic benefit of nearly $400B in the US and Europe alone. The plan noted that “satellite timing is needed to keep our power grids, financial services and mobile networks working …the effects of any outage would be far reaching and potentially very damaging to European economy. To address this threat, it is important to consider backup solutions.”
There was another mysterious GPS outage, this time at the Panama Canal, following the DIA and DFW airport outages. This outage occurred last August and lasted three weeks.
As we enter the most active solar cycle in two decades, there is a concern about how solar weather could impact GPS and other GNSS.
A recent International Telecommunications Union (ITU) paper talked about the importance of synchronization, stating “Synchronization is more important than ever in today’s 5G networks and will be even more so in future mobile networks, where emerging radio technologies and network architectures support increasingly demanding use cases, such as time-sensitive networking for automated vehicles or controlling robots in smart factories.”
A US House Committee held a "Advancing American Leadership in Quantum Technology" hearing focused on reauthorizing the National Quantum Initiative Act, noting that quantum technologies "are changing our nation's economic, strategic, and scientific landscape...and continued American leadership is essential if we want to capture their many benefits."
This article highlights a few tricks to squeeze better performance out of your GNSS signals using ground control points (GCP), post-processed kinematics (PPK), and real-time kinematics (RTK).
The Chicago Quantum Exchange is releasing a “Quick Quantum” video series to teach high-school students about “key concepts in quantum information science and engineering and show how these concepts can be used in real-world applications.”
The More You Know...
It is a common misconception that photons, or particles of light, travel the speed of light.
They do – in a vacuum.
In any other medium, like air, water, or the glass of fiber optics, they move slower than the speed of light (though, in reality, the photon isn't really “slowing down” – it is the effect caused by the photon’s electromagnetic wave interacting with the waves of the medium).
The photon speed can vary based on the properties of the medium and the color/wavelength of the photon.
These variations give up a lot of information about what is happening in the medium.
For example, the photon speed in air depends on pressure, temperature, CO2 concentration, and humidity.
For the glass in an optical fiber, a photon’s speed are set by the glass with slight variations due to physical or temperature shifts. But an accidental break or malicious intrusion could register as a change in the photon’s travel time.
In addition, there is a lot of information that can be gleaned from the travel time of the individual photons.
Each photon has a specific color or wavelength. And for a lot of materials, photons of different colors move at different speeds, which creates the famous prism rainbow effect. In air, glass or water, this means a red photon will arrive at B slightly faster than a purple photon that left A at the same time.
And their relative speed can help provide insight into what is happening between A and B.