Three ways that physicists make their own luck

Sometimes, physicists get really lucky. An experiment can turn up expected results, like when Ernest Rontgen stumbled upon X-rays while investigating cathode rays. But they’re also great at making their own luck. By using mathematical tricks and the rules of quantum mechanics, physicists tip the scales in their favour for everything from detecting gravitational waves to making ever more accurate atomic clocks.

Today’s high-tech experiments often require making detections as such infinitesimally small scales that physicists need to “stack the deck” to increase their chances. From entangling particles to “squeezing” out better results, physicists have found new ways to make precise sensors that help us learn even more about our universe.

1. Detecting gravitational waves with quantum squeezing

Gravitational waves are so difficult to detect that LIGO, a gravitational wave detector in the US, is looking for movements that are 10,0000 trillion times smaller than a human hair. It's so small that the uncertainty principle, one of quantum mechanics' fundamental principles, becomes an issue.

In the uncertainty principle, certain pairs of physical properties, like position and momentum, are limited. The more accurately position is measured, for example, the less accurately momentum can be known. For LIGO, researchers have turned to manipulating the uncertainty principle through a process called “quantum squeezing” to find gravitational waves.

LIGO has released a fantastic short video explanation of quantum squeezing. The process involves increasing the uncertainty in one aspect of light, either the amplitude or phase, to decrease the uncertainty in the other, leading to more accurate detections. LIGO does this at both high and low frequencies to ensure they have the most accurate detections possible.

2. Using entanglement to make more accurate atomic clocks

Another way physicists can “stack the deck” relies on quantum entanglement, the phenomena where particles can share a single joint state so that measuring one instantly determines the others’ state.

In an experiment with many individual particles, each particle gives a weak, noisy signal that requires repeat trials to determine a clear effect. But if you can prepare particles in special entangled states, their detection probabilities together become more strongly correlated.

Entanglement has been explored to make atomic clocks more accurate. Currently, atomic clocks use lasers to measure the vibrations of atoms, which oscillate at a constant frequency. By entangling particles, however, researchers have demonstrated that they can reduce measurement errors that are caused by the statistical uncertainty inherent in quantum mechanics. Acting as an entangled group, the lasers make more accurate detections, increasing the accuracy of atomic clocks.

3. Searching for dark matter and cosmic neutrinos with coherent elastic scattering

Neutrinos are particles that are so small and have such little mass that they can pass through solid lead for a light year before hitting anything. It makes them almost impossible to detect. Currently, increasing the size of neutrino detectors like SNOLAB in Ontario leads to a proportional increase in the chances of a detection, like using a bigger net to go fishing.

But what if you could increase the chances of detection exponentially instead of proportionally?

Asimina Arvanitaki, Stavros Niarchos Foundation Aristarchus Chair in Theoretical Physics at Perimeter, and her fellow researchers have turned to coherent elastic scattering to theorize how to exponentially increase detections. This could change the way experimentalists search for dark matter and cosmic neutrinos.

When atoms experience a high-energy interaction, the amount momentum they transfer makes them easier to locate. But when particles experience weak interactions, they only transfer a small amount of momentum which, because of the uncertainty principle, makes localizing the interaction difficult.

Arvanitaki and her team proved that coherent elastic scattering can square the number of reactions. This is because the low-energy neutrino scatters off an entire nucleus as a single object, leading to a small recoil. If you can prepare the experiment in the right way, you can look for the recoil, increasing detections exponentially.

So, if you’re a budding scientist out there, don’t wait for luck to strike you. Go out and make your own!