Time crystals are a new phase of matter that exhibit a strange property: they are in constant, repeating motion in time without any external input.
Unlike ordinary crystals, which have atoms arranged in a regular pattern in space, time crystals have atoms that oscillate back and forth in time. This means that they break the symmetry of time and behave like a clock.
Time crystals were first proposed by Nobel laureate Frank Wilczek in 2012, but it took until 2016 for the first experimental evidence of their existence to emerge. Since then, scientists have created time crystals in various systems, such as trapped ions, diamond defects, and superfluid helium-3. However, until recently, no one had observed two time crystals in the same system, let alone seen them interact.
A breakthrough experiment
In a breakthrough experiment, published in Nature Materials, an international team of researchers from Lancaster University, Yale University, Royal Holloway London, and Aalto University in Helsinki managed to observe the interaction of two time crystals for the first time ever. They used superfluid helium-3, a rare isotope of helium with one missing neutron, which can form a quantum liquid with zero viscosity and zero entropy at extremely low temperatures.
The researchers cooled superfluid helium-3 to within one ten thousandth of a degree from absolute zero (0.0001 K or -273.15 °C) using a rotating refrigerator at Aalto University. They then created two time crystals inside the superfluid by applying a magnetic field and pumping energy into the system with radio waves. The time crystals consisted of spin waves, or magnons, which are quanta of magnetization that precess about the magnetic field. The magnons formed a Bose-Einstein condensate, a state of matter where all particles occupy the same quantum state and act as one coherent entity.
The researchers then brought the two time crystals close enough to touch and observed how they interacted. They found that the time crystals exchanged particles through a phenomenon known as the Josephson effect, which is usually seen in superconductors. The Josephson effect allows particles to tunnel through a barrier without losing energy or coherence. The researchers also observed that the interaction between the time crystals caused them to change their frequency and phase.
Implications and applications
The observation of two time crystals interacting is a major achievement that opens up new possibilities for studying and manipulating this exotic phase of matter. The researchers hope that their work will inspire further experiments on time crystals in different systems and under different conditions.
One of the potential applications of time crystals is quantum information processing, which aims to use quantum phenomena to perform tasks that are impossible or inefficient with classical computers. Time crystals are attractive for this purpose because they automatically maintain their coherence, which is the main challenge for building quantum devices. Coherence means that the quantum state of a system does not decohere or lose information due to interactions with the environment.
Time crystals could also be used to improve current atomic clock technology, which relies on precise measurements of oscillating atoms to keep accurate time. Atomic clocks are essential for many technologies, such as GPS, telecommunications, and navigation systems. Time crystals could offer advantages over atomic clocks in terms of stability, accuracy, and robustness.
Moreover, time crystals could provide new insights into fundamental physics, such as the nature of time and symmetry breaking. They could also help to detect exotic particles, such as Majorana fermions, which are predicted to exist at the surface of superfluid helium-3 and could enable topological quantum computing.
Time crystals are a fascinating new phase of matter that defy our common sense of time and motion. They have been seen interacting for the first time ever in an experiment using superfluid helium-3. This discovery could lead to novel applications in quantum information processing, atomic clock technology, and fundamental physics.
