From: mk_thisisit
Time crystals are a fascinating concept in physics, often described as the temporal equivalent of ordinary spatial crystals like diamonds or table salt [02:16:18]. Just as spatial crystals exhibit a repeating structure in space, time crystals display periodic motion or behavior in time [02:19:00]. However, this periodicity must emerge spontaneously, distinct from trivial periodic motion such as a clock’s pendulum [04:16:00].
The difficulty in understanding time crystals is acknowledged by many physicists [01:43:00], with the topic being described as “science fiction” [01:53:00]. This complexity arises from their quantum mechanical nature and the subtle ways they break time-translation symmetry.
The Genesis of the Concept
The term “time crystal” was coined by Nobel Prize winner Frank Wilczek in 2012 [00:24:00], [03:28:00]. The name itself is attributed to his wife, who was not a physicist [00:27:00], [10:24:00]. Wilczek’s initial article, originally titled “Spontaneous breaking of symmetry translation in time,” was simplified to the more accessible “time crystal” through his wife’s suggestion [09:56:00].
Wilczek’s original proposal asked whether a system of many bodies could spontaneously enter periodic motion in its lowest energy state, similar to how spatial crystals form [06:36:00], [13:05:00]. This idea centered on the spontaneous breaking of time-translation symmetry [09:27:00]. While the idea was “brilliant” [13:21:00], it was quickly identified that the specific mechanism Frank Wilczek proposed did not work [00:33:00], [11:14:00].
Breakthroughs and Experimental Realization
Despite the initial flaw, Frank Wilczek’s concept opened “powerful horizons for doing new physics” [12:37:00]. Physicists began searching for time crystals in different systems and conditions [13:45:00]. Professor Krzysztof Sacha, recognized as the author of the first description of “discrete time crystals” [15:31:00], contributed a crucial refinement.
Sacha proposed that if a multi-body system is disturbed by a periodically changing force, some systems can spontaneously develop periodic motion with a different period than the driving force [13:52:00]. This “spontaneous emergence of motion periodic which has no direct connection with what drives it” [14:20:00] became the key characteristic of these new time crystals.
Sacha published his article in 2015 [14:49:00]. A year later, two American groups, from the University of Maryland and Harvard, proposed the same phenomenon in other physical systems [14:55:00], [15:08:00]. The following year, the first experiments were successfully carried out, confirming Sacha’s theory [15:04:00].
One significant breakthrough was the realization of a discrete time crystal in an optical system (an optical cavity with laser beams) closer to room temperature conditions [31:48:00]. This contrasts with experiments requiring extremely low temperatures, on the order of nanoKelvins, typically found in specialized laboratories dealing with ultra-cold atomic gases [33:14:00].
Conceptual Challenges in Quantum Mechanics
Understanding time crystals requires grappling with fundamental aspects of quantum mechanics, which describes the world using probabilities [00:57:00].
- Spontaneous Symmetry Breaking: In quantum mechanics, if equations have a certain symmetry, their stationary solutions should also have that symmetry [08:42:48]. However, in phenomena like time crystals, this symmetry is spontaneously broken [09:14:00]. For time crystals, this means a system with continuous time-translation symmetry produces discrete translational symmetry in time, resulting in periodic motion [09:32:00].
- The Observer Effect and Schrödinger’s Cat: A major challenge in quantum mechanics is the “observer point,” where the act of observing elementary particles can change their behavior [20:56:00]. This is illustrated by Schrödinger’s cat analogy: a cat in a box is simultaneously alive and dead (in superposition) until observed [19:10:00]. The information gained from observation collapses the quantum state [19:54:00].
- For time crystals, although a “Schrödinger’s cat” like state might theoretically exist momentarily during formation, it immediately disappears upon observation [23:06:00]. However, the subsequent periodic motion of the time crystal is robust to observation, and the information received does not dramatically change its state [23:24:00].
- Zeno Effect: If a particle is observed continuously, it does not move, an interesting phenomenon called the Zeno effect [25:21:00].
Potential Applications
The field of time crystal applications is still young, but there are promising prospects [26:29:00]. Just as spatial crystals are universally used for their conductivity and transport properties [26:40:00], researchers are exploring if time crystals can exhibit similar properties in the time dimension, such as insulating or even superconductivity properties [27:28:00].
One significant area of interest is their use in quantum computers [26:08:00]. To build a quantum computer, operations must be performed on qubits, which represent quantum information [29:30:00]. This requires entangling qubits, which means they must interact [30:11:00]. A major engineering challenge is maintaining quantum coherence – the property of superposition where a qubit can be both 0 and 1 simultaneously [30:50:00]. While the application of time crystals to quantum computing is currently at a theoretical level, it appears promising [29:17:00].
Broader Implications
The journey of understanding time crystals highlights the dynamic nature of physics, where initial mistakes can lead to new directions of research and profound discoveries [13:19:00]. The field continues to develop, challenging and changing physicists’ points of view [37:47:00].
Ultimately, the study of such abstract concepts also touches upon fundamental philosophical questions. As Frank Wilczek posed the most important unanswered question in science today: “How consciousness is created from matter” [36:14:00], [01:05:00]. This emphasizes that physics, even in its most abstract forms, often grapples with the deepest mysteries of existence.