Scientists evade the Heisenberg uncertainty principle

March 22, 2017
The evolution of a spin and its uncertainty as they orbit due to a magnetic field. The uncertainty, initially equal in all directions, is squeezed into only the out-of-plane component, leaving the two in-plane components highly certain. Credit: ICFO

ICFO Researchers report the discovery of a new technique that could drastically improve the sensitivity of instruments such as magnetic resonance imagers (MRIs) and atomic clocks. The study, published in Nature, reports a technique to bypass the Heisenberg uncertainty principle. This technique hides quantum uncertainty in atomic features not seen by the instrument, allowing the scientists to make very high precision measurements.

State-of-the-art sensors, such as MRIs and atomic clocks, are capable of making measurements with exquisite precision. MRI is used to image tissues deep within the human body and tells us whether we might suffer from an illness, while are extremely precise timekeepers used for GPS, internet synchronization, and long baseline interferometry in radio-astronomy. One might think these two instruments have nothing in common, but they do: both technologies are based on precise measurement the spin of the atom, the gyroscope-like motion of the electrons and the nucleus. In MRI, for example, the pointing angle of the spin gives information about where in the body the atom is located, while the amount of spin (the amplitude) is used to distinguish different kinds of tissue. Combining these two pieces of information, the MRI can make a 3D map of the tissues in the body.

The sensitivity of this kind of measurement was long thought to be limited by Heisenberg's principle, which states that accurately measuring one property of an atom puts a limit to the precision of measurement you can obtain on another property. For example, if we measure an electron's position with high precision, Heisenberg's principle limits the accuracy in the measurement of its momentum. Since most atomic instruments measure two properties (spin amplitude and angle), the principle seems to say that the readings will always contain some . This long-standing expectation has now been disproven, however, by ICFO researchers Dr. Giorgio Colangelo, Ferran Martin Ciurana, Lorena C. Bianchet and Dr. Robert J. Sewell, led by ICREA Prof. at ICFO Morgan W. Mitchell. In their article "Simultaneous tracking of spin angle and amplitude beyond classical limits", published this week in Nature, they describe how a properly designed instrument can almost completely avoid quantum uncertainty.

The trick is to realize that the spin has not one but two pointing angles, one for the north-east-south-west direction, and the other for the elevation above the horizon. The ICFO team showed how to put nearly all of the uncertainty into the angle that is not measured by the instrument. In this way they still obeyed Heisenberg's requirement for uncertainty, but hid the uncertainty where it can do no harm. As a result, they were able to obtain an angle-amplitude measurement of unprecedented precision, unbothered by quantum uncertainty.

Prof. Mitchell uses a solid analogy to state that "To scientists, the uncertainty principle is very frustrating - we'd like to know everything, but Heisenberg says we can't. In this case, though, we found a way to know everything that matters to us. It's like the Rolling Stones song: you can't always get what you want / but if you try sometimes you just might find / you get what you need."

Ferran Martin Ciurana and Dr. Giorgio Colangelo working on the experimental setup. Credit: ICFO

In their study, the ICFO team cooled down a cloud of atoms to a few microKelvin, applied a magnetic field to produce spin motion as in MRI, and illuminated the cloud with a laser to measure the orientation of the atomic spins. They observed that both the spin angle and uncertainty can be continuously monitored with a sensitivity beyond the previously expected limits, although still obeying the Heisenberg principle.

As for the challenges faced during the experiment, Colangelo comments that "in the first place, we had to develop a theoretical model to see if what we wanted to do was really possible. Then, not all the technologies we used for the experiment existed when we started: among them, we had to design and develop a particular detector that was fast enough and with very low noise. We also had to improve a lot the way we were "preparing" the atoms and find a way to efficiently use all the dynamic range we had in the detector. It was a battle against the Dark Side of Quantum, but we won it!"

The results of the study are of paramount importance since this shows that it is possible to obtain even more accurate measurements of atomic spins, opening a new path to the development of far more sensitive instruments and enabling the detection of signals, such as gravitational waves or brain activity, with unprecedented accuracy.

Explore further: Researchers beat the quantum limit of microwave measurements

More information: Simultaneous tracking of spin angle and amplitude beyond classical limits, Nature, nature.com/articles/doi:10.1038/nature21434

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PhysicsMatter
not rated yet Mar 22, 2017
It is all good but it has nothing to do with Werner Heisenberg principle of uncertainty and especially with overcoming its limitation which is anyway theoretical and not really practical due to nature of quantum observables.

Those observables we are dealing in the experiments are large fluxes of particles not individual particles and problem of unwanted influence of act of measurement on outcome of experiment in such a context is not quantum problemor effect at all but it is centuries old issue, well described in manuals of experimentalists and in books on error analysis, as it was elegantly put by Richard von Mises in his famous book, "Probability, Statistics and Truth" 1957, particularly in his critique of Heisenberg uncertainty principle.

More on that and general misinterpretation of Quantum Mechanics in popular science can be found here:
https://questforn...-quanta/

Hyperfuzzy
1 / 5 (2) Mar 25, 2017
This principle applies in QM. Therefore has no basis with reality. Said the superBot with controls for everything.

My super bot challenges your quanta thingy.
charlimopps
not rated yet Mar 27, 2017
Heisenberg compensators?
antialias_physorg
5 / 5 (3) Mar 27, 2017
The study, published in Nature, reports a technique to bypass the Heisenberg uncertainty principle. This technique hides quantum uncertainty in atomic features not seen by the instrument, allowing the scientists to make very high precision measurements.

The article is a bit misleading. They're not breaking the Uncertainty Principle - which is acknowledged in this part:
The ICFO team showed how to put nearly all of the uncertainty into the angle that is not measured by the instrument. In this way they still obeyed Heisenberg's requirement for uncertainty, but hid the uncertainty where it can do no harm.

What they are doing is using squeezed states which lowers uncertainty in one variable at the cost of more uncertainty in another. That's perfectly fine. The trick here is that they shunt all the uncertainty into a variable that is not of interest to the experimental setup.
swordsman
not rated yet Mar 27, 2017
Another example of scientists not understanding the "Heisenberg Uncertainty Principle". This principle is correct in that there is an uncertainty in any time-variant measurement. A simple example is the measurement of velocity of a body. The measurement is time variant in that it takes time to make a measurement, and the particle is moving, thus creating an error. Also, the measurement is vectorial, having a potential direction error. The answer is to take two different vectorial measurements simultaneously. The results can be processed to derive an accurate result. This is not a very difficult scientific problem, with the exception of the proper choice of variables to measure. Unbelievalbe ignorance.
Hyperfuzzy
1 / 5 (1) Mar 27, 2017
No, it's the inability to Quantum Mechanically define a specific state with all measured attributes at a given point in time. Since QM is non-causal, there is no derivable complete state, the world is described erroneously, one cannot define continuity discretely with probabilities; however, one may describe continuity with causality. Knowing every field is "caused" by the motion of charge, and is updated at the speed of light relative to the charge. There are no particles, only these diametrical spherical fields. An infinite set of pairs in an infinite universe; there are no limits except each field center moves as described by Maxwell. These objects are transparent to each other and move according to Coulomb. Therefore one may define exact actions and attributes with inexact measurements. It's called calibration!
antialias_physorg
5 / 5 (2) Mar 27, 2017
This principle is correct in that there is an uncertainty in any time-variant measurement. A simple example is the measurement of velocity of a body. The measurement is time variant in that it takes time to make a measurement,

Uncertainty is independent of measurement method. If it weren't for Uncertainty you could not have something like the tunnelling effect (which is observed and heavily used in electronics). 'Measurement time' or how many measurements you take at the same time is not relevant.
Hyperfuzzy
1 / 5 (1) Mar 28, 2017
This principle is correct in that there is an uncertainty in any time-variant measurement. A simple example is the measurement of velocity of a body. The measurement is time variant in that it takes time to make a measurement,

Uncertainty is independent of measurement method. If it weren't for Uncertainty you could not have something like the tunnelling effect (which is observed and heavily used in electronics). 'Measurement time' or how many measurements you take at the same time is not relevant.

With only the invisible diametrical spherical fields, we call charge, and charge has no mass, charges are transparent to each other but their dance follows coulomb and as they move their fields are updated at the speed of light relative to its center. Their shimmer then is the thing we call energy; for the shimmer will cause motion upon another charge. The rest is defined simply by superposition. Therefore, we may define our measurement exactly.

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