Introduction: Crystals have long captivated scientists and enthusiasts alike due to their intricate structures formed by the orderly arrangement of atoms in a repeating pattern. These atomic configurations give rise to distinct physical properties—such as hardness, conductivity, and optical characteristics.
In 2012, Nobel laureate Frank Wilczek introduced the concept of time crystals, a groundbreaking phase of matter that extends the idea of crystalline order into the realm of time. Unlike ordinary crystals, which exhibit a repeating arrangement of atoms in three-dimensional space, time crystals possess structures that periodically change over time.
A time crystal is a quantum system where particles remain in a state of continuous, repetitive motion, even at their lowest energy level. Since the particles are in the ground state, there is no loss of energy, and the particles do not come to rest. This means they can oscillate between different states without using energy, defying our traditional understanding of thermodynamics and equilibrium.
Time crystals are a remarkable illustration of a new class of non-equilibrium quantum phases of matter. They exhibit a property known as ‘time-translation symmetry breaking,’ which means they switch between different states at regular time intervals. This unusual behavior manifests itself in three main ways:
► Spontaneous Symmetry Breaking: In time crystals, after an initial phase, the system naturally settles into regular oscillations at a period longer than the force driving it. This reflects a stable, self-organized state.
► Crypto-equilibrium: The system’s steady oscillations maintain balance without energy loss or chaos, keeping entropy constant and thereby satisfying the second law of thermodynamics, which dictates that disorder cannot decrease.
► Rigid long-range order: Time crystals maintain synchronized, steady oscillations across long distances and time, staying in harmony even when disturbed by outside influences.
Image Courtesy – https://en.wikipedia.org/wiki/Time_crystal#/media/File:QuantumPhaseTransition.svg
This diagram illustrates the phase transitions between classical and quantum states of matter.
Mechanism:
A regular gallium arsenide crystal was used as the foundation for creating a time crystal, which required breaking symmetry to achieve oscillations between nuclear and electron spins. To do this, about 3% indium atoms were introduced into the crystal through a process called doping, and the crystal was cooled to approximately 6 Kelvin. This doping caused distortions in the crystal lattice, changing the local magnetic fields experienced by the electrons based on how close they were to the Indium atom.
To keep a steady energy supply and balance out energy losses, a pump laser with a wavelength of 785 nanometers was applied. This laser provided both energy and order using circularly polarized light. When the laser hit the crystal, the photons transferred their spin to the electrons, aligning them and boosting them to a higher energy state.
Spin Interactions and Many-Body Localization:
In time crystals, the interactions between particles—specifically the electron and nuclear spinsare central to their behavior. The constant input of laser energy causes electron spins to align.As the electron spins align, their magnetic fields begin to interact with nearby nuclear spins,which in turn exerts a force on the nuclear spins transferring their spin through flip-flop process.However, these nuclear spins don’t align perfectly parallel to the electron spins, which is then pushing back on the same electronic spin leading to a complex oscillating interaction—essentially the first indications of a time crystal.
Localized Eigenstates:
Due to strong interactions and the inherent disorder in the system, the spins (both nuclear and electronic) are restricted to specific localized configurations called eigenstates. In such a system, flipping the spins can lead to a new, stable many-body localized system. This kind of localized behavior is what allows the system to resist spreading out and losing coherence.
Trapped Dynamics:
When the system is driven by an external force, such as a laser, it cycles between two states indefinitely without absorbing energy from the laser.
At the end, a slight magnetic field, tilted at 10 degrees, was added to the system to bias its movement and drive it away from chaotic behavior into a more organized, self-oscillating state. This resulted in oscillations with a repeating pattern and a period of 6.9 seconds—much slower than the oscillations typically seen in optical systems. Remarkably, the time crystal was stable for at least a few hours without noticeable decay during the 40-minute experimental observation.
Key Leaders in the Domain:
Google Quantum AI
- In 2021, Google Quantum AI, in collaboration with NASA and the Universities Space Research Association, worked with Stanford University, Oxford University, and the Max Planck Institute for Physics of Complex Systems to create a time crystal using their Sycamore quantum processor. Google continues to explore the potential of time crystals in quantum computing.
QuTech
- This Dutch research institute is at the forefront of developing time crystals with diamond-based quantum computers, making significant strides in the field.
IBM
- IBM developed Qiskit, an open-source quantum computing framework that has become a standard tool for researchers and developers to write quantum algorithms. Actively researching time crystals to enhance quantum computing capabilities, focusing on qubit performance and error correction.
IonQ
- Specializing in quantum computing, IonQ is investigating time crystals and their potential for improving quantum algorithms and technologies.
- Collaboration between academia and industry can significantly accelerate the development of time crystal technologies. Notable examples of such partnerships include Google Quantum AI and Caltech, who have collaborated on projects, scientists at the University of Maryland, and IBM who have partnered to investigate time crystals and their potential applications in quantum technology. Researchers from Harvard and MIT have collaborated on studies involving many-body physics.
Applications of Time Crystals
- Quantum Memory: Time crystals could serve as nearly perfect quantum memory systems. Their ability to maintain coherence and oscillate between states without energy loss makes them ideal candidates for storing quantum information reliably.
- Enhanced Quantum Algorithms: The unique properties of time crystals can improve the efficiency of quantum algorithms. By leveraging their oscillatory behavior and stability, researchers could develop new algorithms that take advantage of time-dependent states.
- Two-Level Systems: Recent research has shown that coupled time crystals can form macroscopic two-level systems, which exist in a superposition of two independent quantum states. This characteristic allows for precise control over quantum interactions, facilitating advancements in quantum coherence and entanglement studies.
- Room Temperature Quantum Computing: Traditional quantum computers require extremely low temperatures to function effectively. However, time crystals have been demonstrated to exist at room temperature, potentially paving the way for quantum computers that operate without the need for extensive cooling. This could make quantum technology more accessible and practical.
- Quantum Sensors: Time crystals may enable the development of highly sensitive quantum sensors. Their unique oscillatory properties can improve the precision of measurements in various fields, such as magnetometry and gravitational wave detection.
- Study of Quantum Dynamics: Time crystals provide a platform for exploring quantum dynamics and the behavior of many-body systems. Researchers can use them to investigate fundamental questions in quantum physics, contributing to a deeper understanding of the universe.
