Precision Measurements with Quantum Technology


Measurements that are more precise than ever before are now possible thanks to new quantum technologies. 

The precise measurement of physical quantities such as the distance between New York and Boston or the number of electrons flowing through a wire at a particular period may appear to be tedious. 

However, this is not the case. Because, regardless of what is being measured, whether it is meters, seconds, volts, or anything else, the highest level of accuracy may be critical. In this regard, the sensitivity of quantum mechanically entangled states to external shocks can be very beneficial for many measuring applications. 

The measuring of time by atomic clocks is a well-known example of the metrological application of quantum physical processes. 

Optical atomic clocks have been in use for more than 70 years. The characteristic frequency of electron transitions in atoms subjected to electromagnetic radiation determines their temporal interval. 

Incoming electromagnetic waves with a frequency of 9,192,631,770 oscillations per second (in the microwave range) have a maximum resonance for caesium atoms, i.e., a maximum of photons are released at that frequency. 

Humans have a considerably more precise definition of the second than the assertion that one day comprises 86,400 s, thanks to the commonly recognized definition that one second equals 9,192,631,770 of these vibrations. Because atomic clocks are based on the stimulation of numerous caesium atoms and a mean value of the number of released photons is taken, they are extremely precise. 

Now that there are roughly 260 standardized atomic clocks across the world that can be compared to each other, the measurement becomes even more precise, resulting in yet another averaging effect. 

Thanks to a global network of atomic clocks, time measurement is unbelievably precise. Every million years, they are accurate to within 1 second. However, that is insufficiently correct. 

How is that possible? After all, we just need our clock to be precise to the second to ensure that we don't miss the start of our favorite television show. 

However, most of us are unaware that the global navigation system GPS would not function without atomic clocks, as it determines locations by measuring the time it takes for a signal to travel between the device and the GPS satellites. 

The time measurement must be accurate to a few billionths of a second in order to identify our position to within a meter. Similarly, digital communication, in which a huge number of phone calls are sent over a single line at the same time, relies on ultraprecise time measurement. 

Atomic clocks manage the switches that route individual digital signals across the network so that they arrive at the correct receiver in the correct order. 

External disturbances, such as electric fields, can impact the accuracy of atomic clocks. 

These extend the frequency spectrum of the photons being measured, resulting in tiny changes in the resonance frequency and, as a result, in the time being recorded. 

Fluctuations in the terrestrial magnetic field are another factor. Today's GPS and digital communications technologies, as well as high-precision measurements in physics experiments, are limited by this. Even with atomic clocks, time measurement is still too imprecise for some GPS applications or many data transmission channels. 

This weakness would be addressed by a new generation of atomic clocks that take use of quantum entanglement's impact. In each clock in the global network, a few atoms would be quantum mechanically entangled. 

Because a measurement on a single atom of one clock is also a measurement on all others, the clocks will stabilize each other in this way; because to the nature of entanglement, even the tiniest errors within the network of clocks will be instantaneously rectified. 

Quantum physical processes offer another another technique to improve the accuracy of atomic clocks. 

We could account for the unsettling magnetic field variations if we knew how long they lasted in fractions of a second using an adequate error correction approach. Nature demonstrates how the magnetic field may be measured ultra-precisely at the atomic level utilizing the impact of quantum entanglement. 

Many migrating bird species have a magnetic sense that they utilize to navigate hundreds of kilometers to their wintering sites. For a long time, ornithologists were astounded by the precision with which they measured the intensity and direction of the Earth's magnetic field. 

They just discovered a few years ago that birds employ a quantum compass for this reason. Electron pairs are entangled across two molecules by their spins in the robin's eye. 

External magnetic fields are quite sensitive to these entanglements. The electrons revolve in different directions depending on the magnetic field's orientation, which translates to different orientations of their "spin." 

The shift in the orientation of the electron spins of these molecules in the bird's eye is enough to turn them into isomers (molecules with the same chemical formula but different spatial structure). 

The varied characteristics of the isomers are very sensitive to the strength and direction of the magnetic field, generating various chemical processes in the bird's retina that eventually lead to perception—the bird's eye therefore becomes a perfect measuring device for magnetic fields. 

Many species of birds have evolved a form of quantum pair of glasses for magnetic fields. 

They may therefore make their way to their winter lodgings via quantum phenomena. Local gravity fields may be detected extremely precisely utilizing quantum mechanically entangled states, in addition to temporal and magnetic fields, which has sparked major economic interest. 

Today, detailed measurements of the intensity of local gravitational fields are used to find metal and oil resources in the earth. 

Large subterranean gas or water fields can also be detected by local density differences, which result in a slightly greater or weaker gravitational force—but this is a little impact that can only be detected with ultra-sensitive gravity sensors. 

Such measurements might be made much more precise by utilizing the phenomena of quantum mechanical entanglement. Even a single individual might be tracked down using an entanglement-based ultra-sensitive gravity sensor based on the gravitational field formed by their body mass. 

Gas pipelines in the earth, water pipe breaks, sinkholes beneath roadways, and anomalies under a proposed house plot might all be found. 

Furthermore, if archaeologists were able to use gravity sensors to simply "lit up" ancient and prehistoric sites, their work would be substantially simplified. Entanglement-based measuring devices might also detect the small magnetic currents linked to brain function or cell-to-cell communication in our bodies. 

They would allow for real-time monitoring of individual neurons and their behavior. This would allow us to assess the processes in our brain (and body) considerably more precisely than we can now with EEG recordings. 

Quantum magnetic field sensors are already in use for magnetoencephalography (MEG), which uses Superconducting Quantum Interference Devices (SQUIDs) to assess the magnetic activity of the brain (superconducting quantum interference units). Perhaps, in the future, we may be able to capture our thoughts from the outside and feed them straight into a computer. 

Future quantum technologies may, in fact, provide the ideal brain–computer interaction. Much of what has previously been unseen will become visible thanks to measurement instruments based on quantum entanglement.

~ Jai Krishna Ponnappan

You may also want to read more about Quantum Computing here.

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