Breaking Newton’s Law

The interesting oscillatory back-and-forth motion of a quantum particle.

Breaking Newton's Law
Physicists have observed an intriguing oscillatory back-and-forth motion of a quantum particle in a one-dimensional atomic gas. (Credit: Florian Meinert)

A falling apple from a tree makes scientist Issac Newton establish a well-known gravity law. His theory describes the motion of objects subjected to the force. Ranging from a skydiver falling in the earth’s gravitational field to the earth orbiting around the sun, the impact of Newton’s law is evergreen in everyday experience.

In the quantum world, the motion of objects is strongly challenged and may sometimes even completely fail. Scientists at Innsbruck in collaboration with theorists from Munich, Paris, and Cambridge studying a marble falling through water oscillating up and down rather than just moving straight downwards.

In real, scientists have discovered for a quantum particle that’s what scientists called as quantum interference. It is the fact that quantum mechanics allows particles to behave like waves, which can add up or cancel each other.

Scientists primarily cooled down the gas of Cesium atoms to observe the quantum particle oscillating back and forth. They also had to confine it to an arrangement of very thin tubes realized by high-power laser beams.

They then used a simple trick that allows the atoms to interact with each other. At such extreme conditions, the atoms form a quantum fluid whose motion is restricted to the direction of the tubes. Thus, scientists then accelerated an impurity atom, which is an atom in a different spin state, through the gas.

When the quantum particle started moving, they were scattered off the gas particles and to reflect backward. The effect is termed ‘Bragg-scattering’. This causes an oscillatory motion in contrast to what a marble would do when falling in the water.

Scientists found that the experiment failed Newton’s law in the case of the quantum realm.

Scientists explained, “A quantum-wave may get reflected into certain directions has been known since the early days of the development of the theory of quantum mechanics. The surprising thing happened during an experiment, was that no crystal was present for the impurity to reflect off. Instead, it was the gas of atoms itself that provided a type of hidden order in its arrangement, a property that physicist dub ‘correlations’.”

The study suggests that the correlations in combination with the wave-nature of matter determine the motion of particles in the quantum world. It could lead to novel and exciting phenomena that counteract the experiences from our daily life.